IDL Reference Guide: Procedures and Functions

REPEAT...UNTIL

The REPEAT...UNTIL statement repeats its subject statement(s) until an expression evaluates to true. The condition is checked after the subject statement is executed. Therefore, the subject statement is always executed at least once, even if the expression evaluates to true the first time.

Syntax

REPEAT statement UNTIL expression

or

REPEAT BEGIN

   statements

ENDREP UNTIL expression

Examples

This example shows that because the subject of a REPEAT statement is evaluated before the expression, it is always executed at least once:

i = 1  
  
REPEAT BEGIN  
  
   PRINT, i  
  
ENDREP UNTIL (i EQ 1)