$LET: Difference between revisions
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(Created page with "$LET is precompiler command, which is now usable by modern day cavemen to help include and exclude which sections of code compiles in their program based on OS/bit-size or other predefined conditions. {{PageSyntax}} : $LET variable = expression {{PageDescription}} * Unlike LET, $LET is not optional. * $LET a = 12 sets a precompiler variable "a" to the value of 12. This variable is only valid for the precompiler itself and does nothing to affect...") |
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[[$LET]] is precompiler command, which | [[$LET]] is a precompiler command, which helps to include and/or exclude sections of code in a program based on OS/bit-size or other predefined conditions. | ||
| Line 9: | Line 9: | ||
* Unlike [[LET]], [[$LET]] is not optional. | * Unlike [[LET]], [[$LET]] is not optional. | ||
* $LET a = 12 sets a precompiler variable "a" to the value of 12. This variable is only valid for the precompiler itself and does nothing to affect the values of any variable/constant which might also be called "a" in the program. | * $LET a = 12 sets a precompiler variable "a" to the value of 12. This variable is only valid for the precompiler itself and does nothing to affect the values of any variable/constant which might also be called "a" in the program. | ||
* Variable names can | * Variable names must follow QB64's variable naming conventions. | ||
* | * You can check a precompiler variable against special values '''DEFINED''' and '''UNDEFINED''', in order to assess whether the variable has already been assigned a value. Useful for code in libraries which may be repeated. | ||
* The precompiler comes with some preset values which can be used to help determine which code blocks to include/exclude. These are: | |||
** '''WIN''' or '''WINDOWS''' if the user is running QB64 in a Windows environment. | |||
** '''LINUX''' if the user is running QB64 in a Linux environment. | |||
** '''MAC''' or '''MACOSX''' if the user is running QB64 in a macOS environment. | |||
** '''32BIT''' if the user is running a 32-bit version of QB64. | |||
** '''64BIT''' if the user is running a 64-bit version of QB64. | |||
** '''VERSION''', which is set to the version of the QB64 compiler. | |||
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* [[$ELSEIF]] | * [[$ELSEIF]] | ||
* [[$END IF]] | * [[$END IF]] | ||
{{PageNavigation}} | {{PageNavigation}} | ||
Latest revision as of 18:03, 25 November 2022
$LET is a precompiler command, which helps to include and/or exclude sections of code in a program based on OS/bit-size or other predefined conditions.
Syntax
- $LET variable = expression
Description
- Unlike LET, $LET is not optional.
- $LET a = 12 sets a precompiler variable "a" to the value of 12. This variable is only valid for the precompiler itself and does nothing to affect the values of any variable/constant which might also be called "a" in the program.
- Variable names must follow QB64's variable naming conventions.
- You can check a precompiler variable against special values DEFINED and UNDEFINED, in order to assess whether the variable has already been assigned a value. Useful for code in libraries which may be repeated.
- The precompiler comes with some preset values which can be used to help determine which code blocks to include/exclude. These are:
- WIN or WINDOWS if the user is running QB64 in a Windows environment.
- LINUX if the user is running QB64 in a Linux environment.
- MAC or MACOSX if the user is running QB64 in a macOS environment.
- 32BIT if the user is running a 32-bit version of QB64.
- 64BIT if the user is running a 64-bit version of QB64.
- VERSION, which is set to the version of the QB64 compiler.
Examples
- See example 1 in $IF.
See also