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程序循环

Synopsis

DO/label:,index variable,start,end[,increment]

Description

The following provides an effective means of performing a given operation a specified number of times. The operation commonly referred to as a DO loop is a segment of the program which starts with the statement containing the word DO, followed by a slash and a label, and ends with the statement or blank statement which starts with the specified label.

Additional DO loops, referred to as nested loops, may exist inside of a loop, referencing either the same label or a separate label. If a separate label is used in a nested loop, both the DO statement and the specified label statement must exist within the outer loop.

Acceptable Jump Situations:

A jump may be made from a statement inside of a loop to a label which is also inside of the loop.
A jump may be made from a statement inside of a loop to a label which is outside of the loop (this terminates the loop).

Unacceptable Jump Situation:

A jump may not be made from a statement outside of a loop to a label which is inside of a loop.

NOTE: GRIP allows a total of 1000 labels per subroutine. The DO loop generates two labels, the CALL command generates a label, and the IFTHEN/ELSE/ELSEIF/ENDIF uses 2 labels plus 1 for every ELSEIF. These labels count against the total you can use.

Parameters

Parameter

Description

label:

Specifies either the last executable statement in the loop or a blank statement following the last executable statement in the loop.

index variable

A variable which registers the current value of the loop. When the loop is entered the index variable is set to the start value, when the loop is finished the index variable is equal to the end value plus the increment value.

start

The starting value for the loop which may be either a constant, an expression or a variable.

end

The ending value for the loop which may be either a constant, an expression or a variable.

increment

The optional increment value for the loop which may be either a constant, an expression or a variable. If not specified the increment default is 1.

Parameter	Description
label:	Specifies either the last executable statement in the loop or a blank statement following the last executable statement in the loop.
index variable	A variable which registers the current value of the loop. When the loop is entered the index variable is set to the start value, when the loop is finished the index variable is equal to the end value plus the increment value.
start	The starting value for the loop which may be either a constant, an expression or a variable.
end	The ending value for the loop which may be either a constant, an expression or a variable.
increment	The optional increment value for the loop which may be either a constant, an expression or a variable. If not specified the increment default is 1.