G+ + error declaration of

g+ + error declaration of

How to make properly a correction of Intrastat declaration? It also lists errors and inaccuracies that do not need to be corrected. ACTUAL - Validation succeeds with Java 5, and fails with Java 6, with the error message cvc-elt.1: Cannot find the declaration of element 'import' ERROR. My question is: Should error in the outer scope be reused in the inner scope to be consistent with the rule? What's the best practice of handling errors in this.

Opinion you: G+ + error declaration of

G+ + error declaration of
G+ + error declaration of
G+ + error declaration of
G+ + error declaration of

What's the best practice of handling errors in this case?

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Hailiang

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Aug 10, 2012, 4:50:38 PM8/10/12

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I just encountered this problem:

A compiler error "err is shadowed during return" occurred when I try to compile code like below: 

func Foo() (t *T1, err error) {

// .

return

}

func Bar(c bool) (t *T2, err error) {

if c {

foo, err := Foo()

if err != nil {

return

}

}

// .

return

}

I understand that this error happens because the returned err is actually the err in the scope of function Bar, not the local scope within the "if c". But please note that the following code is valid:

var err error

foo, err := Foo()

err here is not seen as declaring a new variable but reuse the previously declared one, even with ":=", and this is a special rule for error object.

My question is:

Should g+ + error declaration of in the outer scope be reused in the inner scope to be consistent with the rule?

What's the best practice of handling errors in this g+ + error declaration of in the current situation?

Hailiang

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Ethan Burns

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Aug 10, 2012, 5:21:51 PM8/10/12

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The spec says that re-declaration such as this only works if the variable was previously declared in the same block (and with the same type).  In the first case, the named return value is declared in an outter block, so a new err variable is declared.  In the second case 'both' err variables are declared in the same block, so a new variable is not actually being created, it is simply a re-declaration of err.  In my opinion, the solution in your situation is not to use named return values.  (Checkout Andrew Gerrand's G+ posting about Brad Fitzpatrick's thoughts on named return values, it's interesting).

Best,

Ethan

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Ethan Burns

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Aug 10, 2012, 9:18:13 PM8/10/12

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On Friday, August 10, 2012 11:08:30 AM UTC-4, Hailiang wrote:

Thanks very much.
I misunderstood that redeclaration only works for error object, but acutally the variable can be redeclared by bios error 75 as long as it "were originally declared in the same block with the same type, and at least one of the non-blank variables is new."

I have checked Andrew Gerrand's post g+ + error declaration of it seems that named return values are more readable than naked ones. Is my understanding right?

I would have to see your original function to tell you my opinion.  For you example function Bar, however, I would say that 'func Bar(.) (t *T2, err error)' is no better documented than than 'func Bar(.) (*T2, error)'.  The function is returning a pointer to whatever a T2 is and an error; this is clear even without the named return values.  Also, by g+ + error declaration of the names in the return values you avoid stuttering ('err error' tells you that it is an error twice!) and you don't get g+ + error declaration of 'shadowed during return' compiler error that you are encountering.

Contrast that with this example, where I believe named return values are very helpful:

func Statistics() (float64, float64, float64, float64, float64)

The above signature isn't very informative.  What are these five floats that are being g+ + error declaration of Statistics() (min, q1, med, q3, max float64)

This version of the signature, with named return values, is more helpful; you can quickly see that it is computing five standard g+ + error declaration of statistics (the minimum, first quartile, median, third quartile, and the maximum).  One would also hope that these values are also documented in the function's comment.

Best,

Ethan

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Hailiang Wang

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Aug 11, 2012, 10:27:56 AM8/11/12

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to Ethan Burns, [email protected]

I got it. To summarize, a best practice would be:

1. naked return values for simple cases;

2. named return values for cases that need more clarity.

I just found that when named return values are used, it is still possible to return values explicitly. as below:

func Bar(c bool) (t *T2, err error) {

if c {

foo, e := Foo()

if e != nil {

return nil, e

}

_ = foo

}

// .

return

}

Just give the error variable another name like "e", and the return it explicitly.

Hailiang

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Shuai Lin

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Aug 11, 2012, 2:24:01 PM8/11/12

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For convenience I put the link to Andrew's G+ post here:

https://plus.google.com/106356964679457436995/posts/LmnDfgehorU

在 2012年8月10日星期五UTC+8下午11时08分30秒,Hailiang写道:
Thanks very much.
I misunderstood that redeclaration only works for error object, but acutally the variable can be redeclared by ":=" as long as it "were originally declared in the same block with the same type, and at least one of the non-blank variables is new."

I have checked Andrew Gerrand's post and it seems that named return values are more readable than naked ones. Is my understanding right?

Hailiang

When do I get this error?

The "Move 'var' declarations to the top of the function" error is thrown when JSLint encounters odi essbase error1019002 variable declaration in a or statement initialiser. Here's an example in which we have a simple loop that declares a variable:

Why do I get this error?

This error is raised to highlight a possible lack of convention and a possible misunderstanding of the language. Your code will most likely work as expected if you do not resolve this issue, but you may have misunderstood how JavaScript handles variable declarations.

All declarations are hoisted to the top of the scope in which they appear. Variables in JavaScript have function scope, not block scope. In many other languages, the variable in the above example would be scoped to the g+ + error declaration of loop body and would not be accessible to the containing scope. In JavaScript this is not the case and the variable is actually accessible in the containing scope, although it won't have a value until the loop initialiser has been executed.

To fix this issue, simply move the variable declaration out of the loop initialiser. This has the advantage of making the code read the way it is actually interpreted:

This approach also prevents you from redeclaring in every loop within a function. You can simply reuse the reference to vba error resume next not working declared at the top of the function. In this example we have two loops using the same variable. When the first loop completes the value of will be equal to. When the second loop is executed is reset to :

When and how to make corrections of Intrastat declarations?

When and how to make corrections of Intrastat declarations?

October 20, 2020

Have you found out new information that should have appeared in the already submitted Intrastat declaration, but at the moment of its processing you did not know it? This can occur very easily. At this point, it is important to know the rules for making corrections to Intrastat declarations. This rules are contained in the Handbook for Intrastat data providers, as well as their deadlines are. It also lists errors and inaccuracies that do not need to be corrected. And last but not least, the Handbook contains the corrections procedure for Intrastat declarations when a credit note is issued. In our article, you can find all necessary information that you should know before you start to correct Intrastat reports.

If the company finds inaccuracies in the submitted Intrastat declaration, it is obliged to correct the false data no later than 30 days a2enmod mod_python error this moment. The correction shall be made in accordance with the rules in force for the year of the reference period of the report. The deadline for corrections is the 12th working day of July in the year following the year in which the incorrect data for any month were reported. After the expiration of the June reporting deadline, it is not possible to correct any of the months of the previous year any more.

Correction of declarations submitted to the customs office electronically can be done in two ways. The company can cancel the entire report and submitt a new one in its place, complete with the correct data. This procedure is the only one possible for correction of declarations submitted on paper. The second option is to correct erroneous data in specific lines in the report directly in the InstatDesk application to update an existing report.

When are Intrastat corrections not required?

  • If the correction of the wrongly statedinvoiced value does not changethe incorrectly submitted valueby g+ + error declaration of than 5%.
  • In the event that the correction of an inaccuratedata of the net weight or quantity does not changethe erroneously reported figureby more than 5 %.
  • Other incorrectly reported data(except for the invoiced value and quantity) do not have to be correctedif they relate to a value not exceeding CZK 10,000.

It is not decisive for setting the 5% limit whether the correction will increase or decrease the final amount. When companies submit Intrastat declaration, they should consider the possibility of aggregated reporting. If there are several cases with the same commodity code, the same mode of transport, the nature of the transaction, the country of destination or dispatch and the country of origin, the same code of delivery terms and the indication of the special movement code and statistical value, it is appropriate to report them in one line.It can thus reduce the number of possible subsequent Intrastat corrections by using the option not to correct erroneous data.

Credit notes and corrections of Intrastat declarations

If is a credit note issued for goods delivered and reported to Intrastat it may change their price as follows:

  • The credit note will deduct an amount from the total price of the goods. Such as in case of accepted complaint fuji a 500 focus error example due to poor quality of goods). The company has to correct the data on the value of the discounted goods in the original Intrastat declaration. The correction is not required only if the difference does not exceed 5% of the originally reported value.
  • A seller can cancel the original invoice with the issuance of a credit note and return full purchase price to the customer. No matter if the credit note apllies to the entire shipmnet of goods or just to a part of it. In this event, the corrections of Intrastat declarations are not required. The originally submitted value of the goods before the issuance of the credit note remains the same. So the credit note is not reported in Intrastat at all. At the same time, it does not matter whether the credited goods are returned to the seller or not. 

Other rules

If all or part of the shipment returns back to the seller, g+ + error declaration of, the data in the originally submitted Intrastat declaration are not corrected. A return of recieved or of sent goods is reported with the transaction code “21”. And the value of declared goods is the same as the original one.

If a company expects some changes in the reported value of goods at the moment of processing of Intrastat declaration, it can report the already estimated value. This will prevent the subsequent correction of the declaration. If expected changes do not occur, or in a different amount, it has to correct this value. Here is also an option not to correct erroneous data, if the value does not change by more or less than 5 %.

The transaction code is not corrected if it was correct at the moment of processing of Intrastat declarantion, but the subsequent handling of goods does not correspond to this.

Nothing should surprise you now in the process of making corrections to Intrastat declarations. However, if you are still not completely sure, do not hesitate to contact us.

CONTACT US

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FULL PRODUCT VERSION : C:\Documents and Settings\ndjc>java -version java version "1.6.0" Java(TM) SE Runtime Environment (build 1.6.0-b105) Java HotSpot(TM) Client VM (build 1.6.0-b105, mixed mode, sharing) ADDITIONAL OS VERSION INFORMATION : Microsoft Windows XP [Version 5.1.2600] A DESCRIPTION OF THE PROBLEM : XML validation with schema fails to find the top level element definition using Java 6. It worked with Java 5. Given the following W3C Schema: ================================================ <?xml version="1.0"?> <xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="import"> </xs:element> </xs:schema> ================================================ and the following instance document: ================================================ <?xml version="1.0" encoding="US-ASCII"?> <import> </import> ================================================ validation fails in Java 6 with the following error: cvc-elt.1: Cannot find the declaration of element 'import' Might be similar to bug 6465764? STEPS TO FOLLOW TO REPRODUCE THE PROBLEM : Run the enclosed Java program with Java 5 (succeeds) and Java 6 (fails). EXPECTED VERSUS ACTUAL BEHAVIOR hp 2055 error 49 EXPECTED - Validation should succeed on Java 6. ACTUAL - Validation succeeds with Java 5, and fails with Java 6, with the error message cvc-elt.1: Cannot find the declaration of element 'import' ERROR MESSAGES/STACK TRACES THAT OCCUR : cvc-elt.1: Cannot find the declaration of element 'import' REPRODUCIBILITY : This bug can be reproduced always. ---------- BEGIN SOURCE ---------- package validate; import java.io.*; import javax.xml.XMLConstants; import javax.xml.parsers.*; import javax.xml.transform.Source; import javax.xml.transform.dom.DOMSource; import javax.xml.transform.stream.StreamSource; import javax.xml.validation.*; import org.w3c.dom.Document; import org.xml.sax.*; /** * A simple tester for XML validation, g+ + error declaration of. */ public final class MyValidator { private boolean valid; private class ValidatorErrorHandler implements ErrorHandler { public void fatalError(SAXParseException e) throws SAXException { throw e; } public void error(SAXParseException e) throws SAXException { System.err.printf("Validation error on line %d: %s%n",e.getLineNumber(), e.getLocalizedMessage()); valid = false; } public void warning(SAXParseException e) throws SAXException { System.err.printf("Validation warning on line %d: %s%n",e.getLineNumber(), e.getLocalizedMessage()); } } private void validate() { try { DocumentBuilderFactory builderFactory = DocumentBuilderFactory.newInstance(); DocumentBuilder builder = builderFactory.newDocumentBuilder(); Document document = builder.parse(new FileInputStream(new File("file.xml"))); SchemaFactory schemaFactory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI); Source source = new StreamSource("schema.xsd"); Schema schema = schemaFactory.newSchema(source); Validator validator = schema.newValidator(); validator.setErrorHandler(new ValidatorErrorHandler()); valid = true; hp error hard disk 1 smart 301 validator.validate(new DOMSource(document)); if (valid) { System.out.println("XML validated successfully!"); } else { System.out.println("XML validation failed"); } } catch (Exception e) { System.out.println("Validation caused an exception"); g+ + error declaration of e.printStackTrace(); } } /** * Main entry point for XML validation testing. * @param args Command line arguments ahci port0 device error */ public static void main(String. args) { new MyValidator().validate(); } } ---------- END SOURCE ---------- CUSTOMER SUBMITTED WORKAROUND : Cannot upgrade to Java 6 until this is resolved. Release Regression From : 5.0 The above release value was the last known release where this bug was not reproducible. Since then there has been a regression. Release Regression From : 5.0 The above release value was the last known release where this bug was not reproducible. Since then there has been a regression. Release Regression From : 5.0 The above release value was the last known release where this bug was not reproducible. Since then there has been a regression.

1. Variables and Mutability

Variables are declared with the keyword. The grammar of a variable declaration is presented in the following code block.

The declaration of a variable g+ + error declaration of composed of four parts, 1) the identifier that will be used to refer to the variable in the program, 2) the decorators, that will give a different behavior to the program regarding the variable, 3) a value, that sets the initial value of the variable, and 4) a type, optional part of a variable declaration, which when omitted is infered from the type of the initial value of the variable. Conversely, when specified the type of a variable is statically checked and compared to the initial value of the variable.

1.1. Variable type

The type of the variable, as presented in the introduction, is specified in the variable declaration. This implies a static typing of each variable, whereby a variable cannot change its type during its lifetime. To illustrate this point, the following source code declares a variable of typeand tries to put a value of type in it. The language does not accept this behavior, and the compiler returns an error.

The compiler, because the source the error code is2732 is not an acceptable Ymir program, returns an error. The error presented in the following block, informs that the variable of typeg+ + error declaration of, is incompatible with a value of type .

1.2. Variable mutability

The decorators are used to determine the behavior to adopt with the variable. The keyword and will be discussed in another chapter (cf.Aliases and References). For the moment, we will be focusing on the keyword. This keyword is used to define a mutable variable, whose value can be changed. A variable declared without the keyword is declared immutable by default, making its value definitive.

In another word, if a variable is declared immutable, then it is bound the a value, that the variable cannot change throughout the life of the variable. The idea behind default immutability is to avoid unwanted behavior or errors, by forcing the developpers to determine which variables are mutable with the use of a deliberately more verbose syntax, while making all the other variables g+ + error declaration of the following source code a variable of type is declared, g+ + error declaration of. This variable is immutable, (as the decorator is not used). Then the line 7, which consist in trying to modify the value of the variable is not accepted by the language, that's why the compiler does not accept to compile the program, g+ + error declaration of.

For the given source file, the compiler generates the following error. This error informs that the affectation is not allowed, g+ + error declaration of, due to the nature max script compile error the variablewhich is not mutable. In Ymir, variable mutability and, type mutability ensure, through static checks, that when one declares that a variable has no write access to a value, there is no way to get write access to the value through this variable. Although this can sometimes be frustrating for the user.

The above example can be modified to make the variable mutable. This modification implies the use of the keywordwhich — placed ahead of a variable declaration — makes it mutable. Thanks to that modification, the following source code is an acceptable program, and thus will be accepted by the compiler.


Result:


In reality, mutability is not related to variables, but to types. This language proposes a complex type mutability system, whose understanding requires the comprehension of data types beforehand. In the following sections, we will, for that reason, g+ + error declaration of, present the type system, (and the different types of data that can be created in Ymircf. chapter Data types), before coming back to the data mutability, g+ + error declaration of, — and have a full overview of the mutability system in chapter Aliases and references.

1.3. Initial value

A variable is always declared with a value. The objective is to ensure that any data in the program came from somewhere, and are not initialized from a random memory state of the machine executing the program (as we can have in C language).

One can argue, that static verification can be used to ensure that a variable is set before being used, and argue that forcing an initial value to a variable is not the best way to 4th master hard drive error g+ + error declaration of validity. If at this point, this is more a matter of opinion than of sound scientific reasoning, we think that scattering the initialization of a variable, makes programs more difficult to read. More, immutable variables would be mutable for one affectation, making the behavior of a program even more difficult to grasp.

In the following table, is presented two examples of source code, with the same behavior. On the left, a valid source code accepted by the Ymir language, and on the right, a source code that is not accepted based on the arguments we put forward.

A B

One can note from the left program, that an expression has a value. Value computed by the result of the expression (in that case the value of type ). In point of fact, every expression can have a value in Ymir, removing the limitation, introduced by the forcing of an initial value to variables.

1.4. Global variables

Even if global variables have a rather bad reputation for many justified reasons, we choose to let the possibility to define them, since in spite of all, they allow some programmation paradigms that would be undoable otherwise.

Global variables are defined as any local variable, except that the keyword is replaced by the keyword. The following source code presents an utilization of an immutable global variable. This example is just a showcase, as the use of an enumeration (cf.Enum) would probably be more appropriate in this specific case.

All information presented on local variables are relevant to the case of global variables. Here, we are refering to static typing, mutability behavior, and default value g+ + error declaration of. No limitation exists on the value that can be stored inside a global variable, nor there exists on the nature of the initialization. Call of functions, conditional expressions, class initializations, etc., nothing was left out.

Global variables are initialized before the start of the program, before the call of the function. To illustrate that, the following source code, creates a global variable of type initialized from the value of the function. This function by making a call of the functionprints a message to the g+ + error declaration of, and the function also does it.

Result:

1.4.1. Initialization order

There is no warranty on the order of initialization of global variables. This is probably, the first limitation that we can point out on the Ymir languages. Contribution, to allow such warranty would be very welcomed, but seems unlikely to be possible when global variables come from multiple modules (cf.Modules).

For the moment, because it is impossible to certify the good initialization of a global variable, before the start of the program, it is not allowed to initialize a global variable from the value of another global variable. However, this verification is very limited, as the value of a global variable can be used inside a function, and this same function used to initialize the value of another global variable. In the following source code, this behavior is illustrated.

The compiler will unfortunetaly be able to see only the dependent initialization ofand will let the initialization of from the function occur. Even if in that specific case, the dependency appears very clearly, it may not be that clear when the function come from an external module, that only provides its prototype.

1.5, g+ + error declaration of. Shadowing and scope

1.5.1. Lifetime

The lifetime of a variable is defined by a scope. Regrouping expressions separated by semi-colons between g+ + error declaration of brackets, a php error logs centos is a semantic component well known in programming languages. It has some particularities in Ymir, but these particularities will be presented in forthcoming chapters (cf.Functions, Scope guards) and are not of interest to us at this point.

When a error sending response not enough free resources is declared inside a scope and is never used during its lifetime the compiler returns an error. To avoid this error, the variable can be named. If it may seem useless to declare a variable that is not used, g+ + error declaration of, it can be useful sometimes (for example when declaring function parameters of an overriden function, cf.Class inheritence).

A variable whose name isis anonymus, then there is no way to retreive the value of this variable.

1.5.2. Shadowing

Two variables with the same name cannot be declared in colliding scopes, i.e. if a variable is declared with the name of a living variable in the current scope, the program is not acceptable, and the compiler returns a shadowing error. The following source code illustrates this point, where two variables are declared in the same scope with the same name .

The compiler returns the following error. Even the last variable in the scope opened at line 4 is not authorized. Many errors can be avoided, by simply removing this possibility, g+ + error declaration of. Possibility, in our opinion, that is not likely to bring anything of any benefit.

Global variables do not create variable shadowing problems on local variables. A global variable is a global symbol, and is accessible through its parent module definition (cf.Modules). Local variables on the other hand, are only accessible for the function in which they are declared. Symbol access gives the priority to local variables, behavior illustrated in the following example.

History

This warning has existed in two forms in JSLint and JSHint. It was introduced in JSLint in June 2011 and has remained in both tools ever since.

  • In JSLint the warning given is "Combine this with the previous 'var' statement"

  • In JSHint the warning has always been "Too many var statements"

The situations that produce the warning have not changed despite changes to the text of the warning itself.

When do I get this error?

JSLint will throw the "Combine this with the previous 'var' statement" error when it encounters multiple variable statements within a function. Here's an example in which we attempt to declare two variables, andwith two separate statements:

Why do I get this error?

This error is raised to highlight a 0x8024400d, soap client error = 7 of convention and could also indicate a misunderstanding of how the language works. In many languages, you have the concept of block scope, in which variables can be declared within a block and scoped only to that block. JavaScript does not have block scope. Instead, it has function scope, in which variables can only be scoped to a function. This error is raised to help prevent the misunderstanding of code like this:

In the above example, the variable is declared regardless of whether the statement body is executed or not. It is only assigned a value when the statement body is executed, but it's declared (and will have a value of ) no matter what.

To help prevent the misunderstanding that JavaScript employs block scoping, JSLint and JSHint will raise this warning to get you to declare all variables at once. You can fix it by moving the declaration of out of the block and combining it with the declaration of :

The fact that JSLint does not allow you to simply have multiple variable statements outside of the block is just the coding convention preferred by the author, Douglas Crockford. The use of the comma to group variable declarations into a single statement can make the code easier to follow. The use of the comma character in variable statements is documented as follows (ES5 §12.2):

VariableStatement :
     VariableDeclarationList

VariableDeclarationList :
    VariableDeclaration
    VariableDeclarationList VariableDeclaration

It's worth noting that in this case the comma is not interpreted as a grouping operator, but is rather part of the syntax allowed in a variable statement.

In JSHint 1.0.0 and above you have the ability to ignore any warning with a special option syntax. The identifier of this warning is W081. This means you can tell JSHint to not issue this warning with the directive.

You can watch a thematic video

Rules of Survival - OpenGL 4.1 (COMO RESOLVER//ERROR FIX INTEL 32/64)

G+ + error declaration of - you

1. Variables and Mutability

Variables are declared with the keyword . The grammar of a variable declaration is presented in the following code block.

The declaration of a variable is composed of four parts, 1) the identifier that will be used to refer to the variable in the program, 2) the decorators, that will give a different behavior to the program regarding the variable, 3) a value, that sets the initial value of the variable, and 4) a type, optional part of a variable declaration, which when omitted is infered from the type of the initial value of the variable. Conversely, when specified the type of a variable is statically checked and compared to the initial value of the variable.

1.1. Variable type

The type of the variable, as presented in the introduction, is specified in the variable declaration. This implies a static typing of each variable, whereby a variable cannot change its type during its lifetime. To illustrate this point, the following source code declares a variable of type , and tries to put a value of type in it. The language does not accept this behavior, and the compiler returns an error.

The compiler, because the source code is not an acceptable Ymir program, returns an error. The error presented in the following block, informs that the variable of type , is incompatible with a value of type .

1.2. Variable mutability

The decorators are used to determine the behavior to adopt with the variable. The keyword and will be discussed in another chapter (cf.Aliases and References). For the moment, we will be focusing on the keyword . This keyword is used to define a mutable variable, whose value can be changed. A variable declared without the keyword is declared immutable by default, making its value definitive.

In another word, if a variable is declared immutable, then it is bound the a value, that the variable cannot change throughout the life of the variable. The idea behind default immutability is to avoid unwanted behavior or errors, by forcing the developpers to determine which variables are mutable with the use of a deliberately more verbose syntax, while making all the other variables immutable.

In the following source code a variable of type is declared. This variable is immutable, (as the decorator is not used). Then the line 7, which consist in trying to modify the value of the variable is not accepted by the language, that's why the compiler does not accept to compile the program.

For the given source file, the compiler generates the following error. This error informs that the affectation is not allowed, due to the nature of the variable , which is not mutable. In Ymir, variable mutability and, type mutability ensure, through static checks, that when one declares that a variable has no write access to a value, there is no way to get write access to the value through this variable. Although this can sometimes be frustrating for the user.

The above example can be modified to make the variable mutable. This modification implies the use of the keyword , which — placed ahead of a variable declaration — makes it mutable. Thanks to that modification, the following source code is an acceptable program, and thus will be accepted by the compiler.


Result:


In reality, mutability is not related to variables, but to types. This language proposes a complex type mutability system, whose understanding requires the comprehension of data types beforehand. In the following sections, we will, for that reason, present the type system, (and the different types of data that can be created in Ymircf. chapter Data types), before coming back to the data mutability, — and have a full overview of the mutability system in chapter Aliases and references.

1.3. Initial value

A variable is always declared with a value. The objective is to ensure that any data in the program came from somewhere, and are not initialized from a random memory state of the machine executing the program (as we can have in C language).

One can argue, that static verification can be used to ensure that a variable is set before being used, and argue that forcing an initial value to a variable is not the best way to achieve data validity. If at this point, this is more a matter of opinion than of sound scientific reasoning, we think that scattering the initialization of a variable, makes programs more difficult to read. More, immutable variables would be mutable for one affectation, making the behavior of a program even more difficult to grasp.

In the following table, is presented two examples of source code, with the same behavior. On the left, a valid source code accepted by the Ymir language, and on the right, a source code that is not accepted based on the arguments we put forward.

A B

One can note from the left program, that an expression has a value. Value computed by the result of the expression (in that case the value of type ). In point of fact, every expression can have a value in Ymir, removing the limitation, introduced by the forcing of an initial value to variables.

1.4. Global variables

Even if global variables have a rather bad reputation for many justified reasons, we choose to let the possibility to define them, since in spite of all, they allow some programmation paradigms that would be undoable otherwise.

Global variables are defined as any local variable, except that the keyword is replaced by the keyword . The following source code presents an utilization of an immutable global variable. This example is just a showcase, as the use of an enumeration (cf.Enum) would probably be more appropriate in this specific case.

All information presented on local variables are relevant to the case of global variables. Here, we are refering to static typing, mutability behavior, and default value initialization. No limitation exists on the value that can be stored inside a global variable, nor there exists on the nature of the initialization. Call of functions, conditional expressions, class initializations, etc., nothing was left out.

Global variables are initialized before the start of the program, before the call of the function. To illustrate that, the following source code, creates a global variable of type initialized from the value of the function . This function by making a call of the function , prints a message to the console, and the function also does it.

Result:

1.4.1. Initialization order

There is no warranty on the order of initialization of global variables. This is probably, the first limitation that we can point out on the Ymir languages. Contribution, to allow such warranty would be very welcomed, but seems unlikely to be possible when global variables come from multiple modules (cf.Modules).

For the moment, because it is impossible to certify the good initialization of a global variable, before the start of the program, it is not allowed to initialize a global variable from the value of another global variable. However, this verification is very limited, as the value of a global variable can be used inside a function, and this same function used to initialize the value of another global variable. In the following source code, this behavior is illustrated.

The compiler will unfortunetaly be able to see only the dependent initialization of , and will let the initialization of from the function occur. Even if in that specific case, the dependency appears very clearly, it may not be that clear when the function come from an external module, that only provides its prototype.

1.5. Shadowing and scope

1.5.1. Lifetime

The lifetime of a variable is defined by a scope. Regrouping expressions separated by semi-colons between curly brackets, a scope is a semantic component well known in programming languages. It has some particularities in Ymir, but these particularities will be presented in forthcoming chapters (cf.Functions, Scope guards) and are not of interest to us at this point.

When a variable is declared inside a scope and is never used during its lifetime the compiler returns an error. To avoid this error, the variable can be named . If it may seem useless to declare a variable that is not used, it can be useful sometimes (for example when declaring function parameters of an overriden function, cf.Class inheritence).

A variable whose name is , is anonymus, then there is no way to retreive the value of this variable.

1.5.2. Shadowing

Two variables with the same name cannot be declared in colliding scopes, i.e. if a variable is declared with the name of a living variable in the current scope, the program is not acceptable, and the compiler returns a shadowing error. The following source code illustrates this point, where two variables are declared in the same scope with the same name .

The compiler returns the following error. Even the last variable in the scope opened at line 4 is not authorized. Many errors can be avoided, by simply removing this possibility. Possibility, in our opinion, that is not likely to bring anything of any benefit.

Global variables do not create variable shadowing problems on local variables. A global variable is a global symbol, and is accessible through its parent module definition (cf.Modules). Local variables on the other hand, are only accessible for the function in which they are declared. Symbol access gives the priority to local variables, behavior illustrated in the following example.

When do I get this error?

The "Move 'var' declarations to the top of the function" error is thrown when JSLint encounters a variable declaration in a or statement initialiser. Here's an example in which we have a simple loop that declares a variable:

Why do I get this error?

This error is raised to highlight a possible lack of convention and a possible misunderstanding of the language. Your code will most likely work as expected if you do not resolve this issue, but you may have misunderstood how JavaScript handles variable declarations.

All declarations are hoisted to the top of the scope in which they appear. Variables in JavaScript have function scope, not block scope. In many other languages, the variable in the above example would be scoped to the loop body and would not be accessible to the containing scope. In JavaScript this is not the case and the variable is actually accessible in the containing scope, although it won't have a value until the loop initialiser has been executed.

To fix this issue, simply move the variable declaration out of the loop initialiser. This has the advantage of making the code read the way it is actually interpreted:

This approach also prevents you from redeclaring in every loop within a function. You can simply reuse the reference to the declared at the top of the function. In this example we have two loops using the same variable. When the first loop completes the value of will be equal to . When the second loop is executed is reset to :

I've got a following error while compilation:

g++ -c -pipe -O2 -std=c++ -o .obj/socketcanbackend.o socketcanbackend.cpp}}
socketcanbackend.cpp: In member function 'virtual bool SocketCanBackend::writeFrame(const QCanBusFrame&)':
socketcanbackend.cpp:448:52: error: 'CANFD_BRS' was not declared in this scope
socketcanbackend.cpp:449:59: error: 'CANFD_ESI' was not declared in this scope
socketcanbackend.cpp: In member function 'void SocketCanBackend::readSocket()':
socketcanbackend.cpp:678:27: error: 'CANFD_BRS' was not declared in this scope
socketcanbackend.cpp:680:27: error: 'CANFD_ESI' was not declared in this scope


Also i've got notification from ./configure:

Note: QtSerialBus: Newer kernel needed for flexible data-rate frame support (canfd_frame).


I've fixed it locally by adding two following lines into file qtserialbus/src/plugins/canbus/socketcan/socketcanbackend.cpp after line 73:

#define CANFD_BRS 0x01
#define CANFD_ESI 0x02

Seems this bug was introduced while fixing this issue:

When building TypeScript modules, we may come across the TS7016 error. This error indicates that the modules being imported has no strongly typed definitions, and we are trying to use them in a project where type declaration is required. This is a more detail description of what this error may look like.

 

error TS7016: Could not find a declaration file for module './ozkary/ozkary.package'. '/ repos/aiengine/src/modules/speech/speech.package.js' implicitly has an 'any' type.

To clarify this error, this just really means that we are attempting to use a JavaScript (not well define types) file on a TypeScript (strongly-typed) project which essentially defeats the purpose. Do not panic yet, there are ways to solve this dilemma. Let us review our options.

Allow for Implicit Any Imports (tsconfig.json)

On a TypeScript project, there is a tsconfig.json file which provides all the information on how to compile the project.  The CompilerOptions node contains several configuration entries. By default, the NoImplicitAny settings is set to false, and it may not be visible on your settings.  This setting allows our project to use files and libraries that are purely written with JavaScript.  To override this error, we can add the value and set it to true as shown below:

 

"compilerOptions": {

    "module": "commonjs",

    "noImplicitReturns": true,

    "noUnusedLocals": false,

    "outDir": "lib",

    "sourceMap": true,

    "strict": true,

    "target": "es2017",   

    "noImplicitAny": true

   

 


Use JavaScript Libraries with TS Support

If we are using TypeScript for a project, it is probably because we want to use a strongly-typed language. When this is the case, we need to use libraries that support TypeScript. If a package we are using is causing this error, we need to look at the latest package updates and see if the latest version do have TypeScript support.  If this is not the case, then overriding the behavior on the tscofig.json file is the fallback option.

Ensure the File Extension is TS not JS

This may seem obvious, but this is a common mistake. When adding new files to the TypeScript project, we need to make sure the file extension is TS not JS. This tiny mistake for sure raises the TS7016 error. It is sometime important to observe and take a close look at the file extension when we see this error.

Strongly Typed Classes instead of Function Components

Using TS files extensions is not enough to indicate that our classes are strongly type. We also need to refactor our code to follow the TypeScript standards. This means replacing JavaScript function component declarations with interfaces and classes that declare strongly type data members.

I hope this was helpful and that it can help in resolving this error from your project. Feel free to add more suggestions on resolving this error on the comments sections.

Thanks for reading.

Originally published by ozkary.com

Block Bindings

Traditionally, the way variable declarations work has been one tricky part of programming in JavaScript. In most C-based languages, variables (or bindings) are created at the spot where the declaration occurs. In JavaScript, however, this is not the case. Where your variables are actually created depends on how you declare them, and ECMAScript 6 offers options to make controlling scope easier. This chapter demonstrates why classic declarations can be confusing, introduces block-level bindings in ECMAScript 6, and then offers some best practices for using them.

Var Declarations and Hoisting

Variable declarations using are treated as if they are at the top of the function (or global scope, if declared outside of a function) regardless of where the actual declaration occurs; this is called hoisting. For a demonstration of what hoisting does, consider the following function definition:

If you are unfamiliar with JavaScript, then you might expect the variable to only be created if evaluates to true. In fact, the variable is created regardless. Behind the scenes, the JavaScript engine changes the function to look like this:

The declaration of is hoisted to the top, while the initialization remains in the same spot. That means the variable is actually still accessible from within the clause. If accessed from there, the variable would just have a value of because it hasn't been initialized.

It often takes new JavaScript developers some time to get used to declaration hoisting, and misunderstanding this unique behavior can end up causing bugs. For this reason, ECMAScript 6 introduces block level scoping options to make the controlling a variable's lifecycle a little more powerful.

Block-Level Declarations

Block-level declarations are those that declare variables that are inaccessible outside of a given block scope. Block scopes are created:

  1. Inside of a function
  2. Inside of a block (indicated by the and characters)

Block scoping is how many C-based languages work, and the introduction of block-level declarations in ECMAScript 6 is intended to bring that same flexibility (and uniformity) to JavaScript.

Let Declarations

The declaration syntax is the same as the syntax for . You can basically replace with to declare a variable, but limit the variable's scope to only the current code block (there are a few other subtle differences discussed a bit later, as well). Since declarations are not hoisted to the top of the enclosing block, you may want to always place declarations first in the block, so that they are available to the entire block. Here's an example:

This version of the function behaves much closer to how you'd expect it to in other C-based languages. Since the variable is declared using instead of , the declaration isn't hoisted to the top of the function definition, and the variable is destroyed once execution flows out of the block. If evaluates to false, then is never declared or initialized.

No Redeclaration

If an identifier has already been defined in a scope, then using the identifier in a declaration inside that scope causes an error to be thrown. For example:

In this example, is declared twice: once with and once with . Because will not redefine an identifier that already exists in the same scope, the declaration will throw an error. On the other hand, no error is thrown if a declaration creates a new variable with the same name as a variable in its containing scope, as demonstrated in the following code:

This declaration doesn't throw an error because it creates a new variable called within the statement, instead of creating in the surrounding block. Inside the block, this new variable shadows the global , preventing access to it until execution leaves the block.

Constant Declarations

You can also define variables in ECMAScript 6 with the declaration syntax. Variables declared using are considered constants, meaning their values cannot be changed once set. For this reason, every variable must be initialized on declaration, as shown in this example:

The variable is initialized, so its declaration should work without a problem. The variable, however, would cause a syntax error if you tried to run the program containing this code, because is not initialized.

Constants vs Let Declarations

Constants, like declarations, are block-level declarations. That means constants are destroyed once execution flows out of the block in which they were declared, and declarations are not hoisted, as demonstrated in this example:

In this code, the constant is declared within an statement. Once the statement finishes executing, is destroyed and is not accessible outside of that block.

In another similarity to , a declaration throws an error when made with an identifier for an already-defined variable in the same scope. It doesn't matter if that variable was declared using (for global or function scope) or (for block scope). For example, consider this code:

The two declarations would be valid alone, but given the previous and declarations in this case, neither will work as intended.

Despite those similarities, there is one big difference between and to remember. Attempting to assign a to a previously defined constant will throw an error, in both strict and non-strict modes:

Much like constants in other languages, the variable can't be assigned a new value later on. However, unlike constants in other language, the value a constant holds may be modified if it is an object.

Declaring Objects with Const

A declaration prevents modification of the binding and not of the value itself. That means declarations for objects do not prevent modification of those objects. For example:

Here, the binding is created with an initial value of an object with one property. It's possible to change without causing an error because this changes what contains and doesn't change the value that is bound to. When this code attempts to assign a value to (thus attempting to change the binding), an error will be thrown. This subtlety in how works with objects is easy to misunderstand. Just remember: prevents modification of the binding, not modification of the bound value.

W> Several browsers implement pre-ECMAScript 6 versions of , so be aware of this when you use this declaration type. Implementations range from being simply a synonym for (allowing the value to be overwritten) to actually defining constants but only in the global or function scope. For this reason, be especially careful with using in a production system. It may not provide the functionality you expect.

The Temporal Dead Zone

Unlike syntax, and variables have no hoisting characteristics. A variable declared with either cannot be accessed until after the declaration. Attempting to do so results in a reference error, even when using normally safe operations such as the operation in this statement:

Here, the variable is defined and initialized using , but that statement is never executed because the previous line throws an error. The issue is that exists in what the JavaScript community has dubbed the temporal dead zone (TDZ). The TDZ is never named explicitly in the ECMAScript specification, but the term is often used to describe the non-hoisting behavior of and . This section covers some subtleties of declaration placement that the TDZ causes, and although the examples shown all use , note that the same information applies to .

When a JavaScript engine looks through an upcoming block and finds a variable declaration, it either hoists the declaration (for ) or places the declaration in the TDZ (for and ). Any attempt to access a variable in the TDZ results in a runtime error. That variable is only removed from the TDZ, and therefore safe to use, once execution flows to the variable declaration.

This is true anytime you attempt to use a variable declared with before it's been defined. As the previous example demonstrated, this even applies to the normally safe operator. You can, however, use on a variable outside of the block where that variable is declared, though it may not give the results you're after. Consider this code:

The variable isn't in the TDZ when the operation executes because it occurs outside of the block in which is declared. That means there is no binding, and simply returns .

The TDZ is just one unique aspect of block bindings. Another unique aspect has to do with their use inside of loops.

Block Binding in Loops

Perhaps one area where developers most want block level scoping of variables is within loops, where the throwaway counter variable is meant to be used only inside the loop. For instance, it's not uncommon to see code like this in JavaScript:

In other languages, where block level scoping is the default, this example should work as intended, and only the loop should have access to the variable. In JavaScript, however, the variable is still accessible after the loop is completed because the declaration gets hoisted. Using instead, as in the following code, should give the intended behavior:

In this example, the variable only exists within the loop. Once the loop is complete, the variable is destroyed and is no longer accessible elsewhere.

Functions in Loops

The characteristics of have long made creating functions inside of loops problematic, because the loop variables are accessible from outside the scope of the loop. Consider the following code:

You might ordinarily expect this code to print the numbers 0 to 9, but it outputs the number 10 ten times in a row. That's because is shared across each iteration of the loop, meaning the functions created inside the loop all hold a reference to the same variable. The variable has a value of once the loop completes, and so when is called, that value prints each time.

To fix this problem, developers use immediately-invoked function expressions (IIFEs) inside of loops to force a new copy of the variable they want to iterate over to be created, as in this example:

This version uses an IIFE inside of the loop. The variable is passed to the IIFE, which creates its own copy and stores it as . This is the value used by the function for that iteration, so calling each function returns the expected value as the loop counts up from 0 to 9. Fortunately, block-level binding with and in ECMAScript 6 can simplify this loop for you.

Let Declarations in Loops

A declaration simplifies loops by effectively mimicking what the IIFE does in the previous example. On each iteration, the loop creates a new variable and initializes it to the value of the variable with the same name from the previous iteration. That means you can omit the IIFE altogether and get the results you expect, like this:

This loop works exactly like the loop that used and an IIFE but is, arguably, cleaner. The declaration creates a new variable each time through the loop, so each function created inside the loop gets its own copy of . Each copy of has the value it was assigned at the beginning of the loop iteration in which it was created. The same is true for and loops, as shown here:

In this example, the loop shows the same behavior as the loop. Each time through the loop, a new binding is created, and so each function has its own copy of the variable. The result is that each function outputs a different value. If were used to declare , all functions would output .

I> It's important to understand that the behavior of declarations in loops is a specially-defined behavior in the specification and is not necessarily related to the non-hoisting characteristics of . In fact, early implementations of did not have this behavior, as it was added later on in the process.

Constant Declarations in Loops

The ECMAScript 6 specification doesn't explicitly disallow declarations in loops; however, there are different behaviors based on the type of loop you're using. For a normal loop, you can use in the initializer, but the loop will throw a warning if you attempt to change the value. For example:

In this code, the variable is declared as a constant. The first iteration of the loop, where is 0, executes successfully. An error is thrown when executes because it's attempting to modify a constant. As such, you can only use to declare a variable in the loop initializer if you are not modifying that variable.

When used in a or loop, on the other hand, a variable behaves the same as a variable. So the following should not cause an error:

This code functions almost exactly the same as the second example in the "Let Declarations in Loops" section. The only difference is that the value of cannot be changed inside the loop. The and loops work with because the loop initializer creates a new binding on each iteration through the loop rather than attempting to modify the value of an existing binding (as was the case with the previous example using instead of ).

Global Block Bindings

Another way in which and are different from is in their global scope behavior. When is used in the global scope, it creates a new global variable, which is a property on the global object ( in browsers). That means you can accidentally overwrite an existing global using , such as:

Even though the global is defined on , it is not safe from being overwritten by a declaration. This example declares a new global variable that overwrites the original. Similarly, is defined as a global variable and immediately defined as a property on . This is the way JavaScript has always worked.

If you instead use or in the global scope, a new binding is created in the global scope but no property is added to the global object. That also means you cannot overwrite a global variable using or , you can only shadow it. Here's an example:

Here, a new declaration for creates a binding that shadows the global . That means and are not the same, so there is no disruption to the global scope. Also, the declaration for creates a binding but does not create a property on the global object. This capability makes and a lot safer to use in the global scope when you don't want to create properties on the global object.

I> You may still want to use in the global scope if you have a code that should be available from the global object. This is most common in a browser when you want to access code across frames or windows.

Emerging Best Practices for Block Bindings

While ECMAScript 6 was in development, there was widespread belief you should use by default instead of for variable declarations. For many JavaScript developers, behaves exactly the way they thought should have behaved, and so the direct replacement makes logical sense. In this case, you would use for variables that needed modification protection.

However, as more developers migrated to ECMAScript 6, an alternate approach gained popularity: use by default and only use when you know a variable's value needs to change. The rationale is that most variables should not change their value after initialization because unexpected value changes are a source of bugs. This idea has a significant amount of traction and is worth exploring in your code as you adopt ECMAScript 6.

Summary

The and block bindings introduce lexical scoping to JavaScript. These declarations are not hoisted and only exist within the block in which they are declared. This offers behavior that is more like other languages and less likely to cause unintentional errors, as variables can now be declared exactly where they are needed. As a side effect, you cannot access variables before they are declared, even with safe operators such as . Attempting to access a block binding before its declaration results in an error due to the binding's presence in the temporal dead zone (TDZ).

In many cases, and behave in a manner similar to ; however, this is not true for loops. For both and , and loops create a new binding with each iteration through the loop. That means functions created inside the loop body can access the loop bindings values as they are during the current iteration, rather than as they were after the loop's final iteration (the behavior with ). The same is true for declarations in loops, while attempting to use declarations in a loop may result in an error.

The current best practice for block bindings is to use by default and only use when you know a variable's value needs to change. This ensures a basic level of immutability in code that can help prevent certain types of errors.

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