Advanced Programming Techniques in D/

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Labels and goto

Labels and goto

Learn the use of labels and the “goto” keyword.

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Labels

Labels are names given to lines of code in order to direct program flow to those lines later on.

A label consists of a name and the : character:

end:   // ← a label

This label gives the name end to the line that it is defined on.

Note: In reality, a label can appear between statements on the same line to name the exact spot that it appears, but this is not a common practice:

anExpression(); end: anotherExpression();

goto

goto directs program flow to the specified label:

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import std.stdio;



void foo(bool condition) { 

    writeln("first");



    if (condition) {

        goto end; 

    }



    writeln("second"); 



end:



    writeln("third"); 

}



void main ()

{

    foo(true);

}

When the condition is true, the program flow goes to label end, effectively skipping the line that prints “second.”

goto works the same way as in the C and C++ programming languages. Being notorious for making it hard to understand the intent and flow of code, goto ...