Editing For loop (section)

===Vectorised for-loops===
Some languages offer a for-loop that acts as if processing all iterations [[Automatic vectorization|in parallel]], such as the {{code|for all}} keyword in [[Fortran 95]] which has the interpretation that ''all'' [[Sides of an equation|right-hand-side]] expressions are evaluated before ''any'' assignments are made, as distinct from the explicit iteration form. For example, in the {{code|for}} statement in the following pseudocode fragment, when calculating the new value for {{code|A(i)}}, except for the first (with {{code|1=i = 2}}) the reference to {{code|A(i - 1)}} will obtain the new value that had been placed there in the previous step. In the {{code|for all}} version, however, each calculation refers only to the original, unaltered {{code|A}}.
 '''for'''     i := 2 : N - 1 '''do''' A(i) := [A(i - 1) + A(i) + A(i + 1)] / 3; '''next''' i;
 '''for all''' i := 2 : N - 1 '''do''' A(i) := [A(i - 1) + A(i) + A(i + 1)] / 3;
The difference may be significant.

Some languages (such as PL/I, Fortran 95) also offer array assignment statements, that enable many for-loops to be omitted. Thus pseudocode such as {{code|1=A:= 0;}} would set all elements of array A to zero, no matter its size or dimensionality. The example loop could be rendered as
<syntaxhighlight lang="Fortran">
 A(2 : N - 1) := [A(1 : N - 2) + A(2 : N - 1) + A(3 : N)] / 3;
</syntaxhighlight>
But whether that would be rendered in the style of the for-loop or the for-all-loop or something else may not be clearly described in the compiler manual.