IBM SC34-5764-01 Manual do Utilizador descarregar pdf (Página 169)

100

101

ITERATE

Purpose

 ITERATE

name

; 

ITERATE alters the flow within a repetitive DO loop (that is, any DO construct other than that with a simple

DO).

Execution of the group of instructions stops, and control is passed to the DO instruction just as though the

END clause had been encountered. The control variable (if any) is incremented and tested, as usual, and

the group of instructions is processed again, unless the DO instruction ends the loop.

The name is a symbol, taken as a constant. If name is not specified, ITERATE steps the innermost active

repetitive loop. If name is specified, it must be the name of the control variable of a currently active loop

(which may be the innermost), and this is the loop that is stepped. Any active loops inside the one

selected for iteration are ended (as though by a LEAVE instruction).

Example:

do i=1 to 4

if i=2 then iterate

say i

end

/* Displays the numbers: "1" "3" "4" */

Notes:

1. If specified, name must match the symbol naming the control variable in the DO clause in all respects

except case. No substitution for compound variables is carried out when the comparison is made.

2. A loop is active if it is currently being processed. If a subroutine is called (or an INTERPRET

instruction is processed) during execution of a loop, the loop becomes inactive until the subroutine has

returned or the INTERPRET instruction has completed. ITERATE cannot be used to step an inactive

loop.

3. If more than one active loop uses the same control variable, ITERATE selects the innermost loop.

ITERATE

Chapter 13. Keyword Instructions 147

1 2 ... 164 165 166 167 168 169 170 171 172 173 174 ... 480 481

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