Editing For loop (section)

===1968: ALGOL 68===
{{Further|ALGOL 68}}
ALGOL 68 has what was considered ''the'' universal loop, the full syntax is:
<pre>
FOR i FROM 1 BY 2 TO 3 WHILE i≠4 DO ~ OD
</pre>

Further, the single iteration range could be replaced by a list of such ranges. There are several unusual aspects of the construct
* only the {{code|do ~ od}} portion was compulsory, in which case the loop will iterate indefinitely.
* thus the clause {{code|to 100 do ~ od}}, will iterate exactly 100 times.
* The {{code|while}} ''syntactic element'' allowed a programmer to break from a {{code|for}} loop early, as in:
<pre>
INT sum sq := 0;
FOR i
 WHILE
  print(("So far:", i, new line)); # Interposed for tracing purposes. #
  sum sq ≠ 70↑2                    # This is the test for the WHILE   #
DO
  sum sq +:= i↑2
OD
</pre>

Subsequent ''extensions'' to the standard ALGOL 68 allowed the {{code|to}} syntactic element to be replaced with {{code|{{sic|hide=y|up|to}}}} and {{code|downto}} to achieve a small optimization. The same compilers also incorporated:
;{{code|until}}: for late loop termination.
;{{code|foreach}}: for working on arrays in [[parallel computing|parallel]].