Variables, user-written procedures, and user-written functions should not have the same names as IDL functions or procedures. Re-using names of IDL routines can lead to syntax errors or to “hiding” variables. In addition, certain words representing IDL language constructs are strictly forbidden—using any of these reserved words as a variable, procedure, or function name will cause an immediate syntax error. The following table lists all of the reserved words in IDL.

AND                           

BEGIN                     

BREAK                            

CASE

COMMON

COMPILE_OPT

CONTINUE

DO

ELSE

END

ENDCASE

ENDELSE

ENDFOR

ENDFOREACH

ENDIF

ENDREP

ENDSWITCH

ENDWHILE

EQ

FOR

FOREACH

FORWARD_FUNCTION FUNCTION GE

GOTO

GT

IF

INHERITS LE

LT

MOD

NE NOT
OF ON_IOERROR

OR

PRO

REPEAT

SWITCH

THEN UNTIL

WHILE

XOR