IDL Reference Guide: Procedures and Functions

IF...THEN...ELSE

The IF...THEN...ELSE statement conditionally executes a statement or block of statements.

Syntax

IF expression THEN statement [ ELSE statement ]

or

IF expression THEN BEGIN

   statements

ENDIF [ ELSE BEGIN

   statements

ENDELSE ]

Examples

The following example illustrates the use of the IF statement using the ELSE clause. Notice that the IF statement is ended with ENDIF, and the ELSE statement is ended with ENDELSE. Also notice that the IF statement can be used with or without the BEGIN...END block:

A = 2  
B = 4  
  
IF (A EQ 2) AND (B EQ 3) THEN BEGIN  
   PRINT, 'A = ', A  
   PRINT, 'B = ', B  
ENDIF ELSE BEGIN  
   IF A NE 2 THEN PRINT, 'A <> 2' ELSE PRINT, 'B <> 3'  
ENDELSE  

IDL Prints:

B <> 3