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Explanation in .NET Draw PDF417 in .NET Explanation

Example 11.5. using .net vs 2010 todraw pdf417 for asp.net web,windows application Quick Response Code (The Script) #Passing argum PDF-417 2d barcode for .NET ents 1 $first="Charles"; $last="Dobbins"; 2 &greeting ( $first, $last ); 3 sub greeting{ 4 print "@_", "\n"; 5 print "Welcome to the club, $_[0] $_[1]!\n";. (Output) 4 Charles Dobbins 5 Welcome to the club, Charles Dobbins!. Explanation 1. Scalars are assigned values. 2. The greeting subroutine is called with two parameters, $first and $last. 3. The subroutine is declared. 4. The parameters are store .net framework barcode pdf417 d in the @_ array, a local array that is created when the subroutine is entered and is removed when the subroutine exits.

It contains references to the $first and $last.. 5. The first two elements o f the @_ array are printed. The individual elements are represented as scalars $_[0] and $_[1].

. 6. The closing curly brace visual .net PDF 417 marks the end of the subroutine definition.

@_ will disappear. Example 11.6.

. Explanation 1. The subroutine params is defined. 2. The value of @_, the act ual parameter list, is printed. @_ is a local array referencing any arguments passed to the subroutine.

. 3. The first value of the @_ array is printed. 4. The last element of the array is removed with the pop function and then printed. 5. The foreach loop assigns, in turn, to scalar $value each element of the @_ array. 6. Each element of the array is incremented by 5 and stored in the scalar $value. 7. After the user has typed PDF417 for .NET five numbers, the split function returns an array consisting of each of the numbers read from STDIN.

. 8. The subroutine is called, passing the array as a parameter. 9. The values printed illus PDF 417 for .NET trate that those values changed in the function were really changed.

The only value that wasn"t changed is the last element of the original array. The reference to it was popped in line 4 of the subroutine..

Call-by-Value with local and my Most programming languages .net vs 2010 pdf417 provide a way for you to pass arguments so that the original values are not altered by the subroutine. When an argument is passed using a call-by-value, a copy of the value of the argument is sent to the subroutine.

If the copy is modified, the original value is untouched. To make copies of values in Perl, the arguments are copied from the @_ array and assigned to local variables. Perl provides two built-in functions, local and my, to create local copies.

. The local Function The local function was used visual .net PDF417 to turn on call-by-value in Perl programs prior to the Perl 5 release. Now the my operator is used, which further ensures the privacy of variables within a function block.

The local function creates local variables from its list. Any variable declared with local is said to be dynamically scoped, which means it is visible from within the block where it was created and visible to any functions called from within this block or any blocks (or subroutines) nested within the block where it is defined. If a local variable has the same name as a global variable, the value of the global one is saved and a new local variable is temporarily created.

When the local variable goes out of scope, the global variable becomes visible again with its original value(s) restored. After the last statement in a subroutine is executed, its local variables are discarded. It is recommended that all local variables be set at the beginning of the subroutine block.

. Figure 11.1. The @_ references the actual scalar parameters. Example 11.7. (The Script) 1 $first="Per" ; $last="Lindberg"; 2 &greeting ( $first, $last ) ; # Call the greeting subroutine 3 print "---$fname---\n" if defined $fname; # $fname is local to # sub greeting # Subroutine defined sub greeting{ 4 local ($fname, $lname) = @_ ; 5 print "Welcome $fname!!\n"; } (Output) 3 <no output> 5 Welcome Per!!. # Call by value Explanation 1. The scalar variables are assigned values. 2. A call is made to the greeting subroutine. Two arguments are passed. 3. The print statement is n PDF417 for .NET ot executed, because $fname is not defined here.

It was defined as a local variable in the subroutine. It is local to the greeting subroutine..

4. The local function takes a list of arguments from the @_ array and creates two local variables, $fname and $lname, from that list. The values in the local variables are copies of the values that were passed.

This mechanism is called "pass by value.". 5. The print statement is e barcode pdf417 for .NET xecuted.

The contents of the local variable $fname are printed, which is a copy of what is in $first..
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