for loop's

What is translated > Statements > for loop's

Delphi supports two kinds of 'for' loops:

In a counter-based Delphi loop, the initial and final expressions are evaluated exactly once, before the loop starts. In C++, however, the loop condition is evaluated before every iteration. This difference requires special handling during translation.

In the following example, the original value of 'n' determines the number of iterations:

procedure Test;

var

  I, n: Integer;

begin

  n := 10;

  for I := 1 to n do

  begin

    DoSomething;

    n := 11;

  end;

end;

A straightforward translation would be:

int I = 0;

int n = 0;

n = 10;

for (I = 1; I <= n; ++I)

{

    DoSomething();

    n = 11;

}

This translation does not preserve the Delphi behavior. In C++, the condition 'I <= n' is evaluated before every iteration. Because 'n' is changed to '11' inside the loop, C++ executes an additional iteration.

To preserve the Delphi semantics, the original final value must be stored before the loop starts:

int I = 0;

int n = 0;

n = 10;

const int stop = n;

for (I = 1; I <= stop; ++I)

{

    DoSomething();

    n = 11;

}

Delphi2Cpp can generate either form, depending on the Use "stop" variable in for-loop** option.

Delphi2Cpp also checks whether the type of the loop variable can safely represent the value required to terminate the generated C++ loop. If necessary, it replaces the loop variable with a wider type. See Loop Variable Type for details.

This page belongs to the Delphi2Cpp Documentation