WHILE

Syntax

WHILE logical_expression

The general format of a WHILE command is:

WHILE logical_expression SQR_commands... [BREAK] SQR_commands... END-WHILE

Description

Begins a WHILE ... END-WHILE loop.

The WHILE loop continues until the condition being tested is FALSE.

An expression returning 0 (zero) is considered FALSE; an expression returning nonzero is TRUE.

BREAK causes an immediate exit of the WHILE loop; SQR continues with the command immediately following END-WHILE.

WHILE commands can be nested to any level and can include or be included within IF and EVALUATE commands.

Parameters

Parameter	Description
logical_expression	A valid logical expression. See the LET command for a description of logical expressions.

Example

This example shows an IF nested within a WHILE:

while #count < 50
    do get_statistics
    if #stat_count = 100
       break     ! Exit WHILE loop.
    end-if
    add 1 to #count
end-while

You can use single numeric variables in your expression to make your program more readable, for example, when using flags:

move 1 to #have_data
...
 while #have_data
   ...processing...
end-while

This example sets up an infinite loop:

while 1
    ...processing...
    if ...
       break     ! Exit loop
    end-if
end-while

Any complex expression can be used in the WHILE command, as shown in this example:

while #count < 100 and (not #end-file or isnull(&state))
   ...
end-while

SeeThe LET command for a description of expressions.