OPTION EXPLICIT: Difference between revisions

Latest revision as of 15:19, 25 September 2024

OPTION _EXPLICIT instructs the compiler to require variable declaration with DIM, REDIM or an equivalent statement.

With OPTION _EXPLICIT you can avoid typos by having QB64 immediately warn in the Status area of new variables used without previous declaration.
The use of OPTION _EXPLICIT does also enforce the requirement to DIM or REDIM any arrays before first use, no extra OPTION _EXPLICITARRAY is needed.
Enable OPTION _EXPLICIT temporarily even if a program source file doesn't contain the directive by specifying the -e switch when compiling via command line (qb64 -c file.bas -e).

If used, OPTION _EXPLICIT must be the very first statement in your program. No other statements can precede it (except for comment lines started with an apostrophe or REM).
Do not use OPTION _EXPLICIT in $INCLUDEd modules.

Example: Avoiding simple typos with OPTION _EXPLICIT results shown in the QB64 IDE Status area.

OPTION _EXPLICIT

DIM myVariable AS INTEGER

myVariable = 5

PRINT myVariabe

QB64 IDE Status will show: Variable 'myVariabe' (SINGLE) not defined on line 4

@@ Line 13: / Line 13: @@
 === Errors ===
-* If used, [[OPTION _EXPLICIT]] must be the very first statement in your program. No other statements can precede it (except for [[$NOPREFIX]] or comment lines started with an [[Apostrophe|apostrophe]] or [[REM]]).
+* If used, [[OPTION _EXPLICIT]] must be the very first statement in your program. No other statements can precede it (except for comment lines started with an [[Apostrophe|apostrophe]] or [[REM]]).
 * Do not use [[OPTION _EXPLICIT]] in [[$INCLUDE]]d modules.