Macro
(define-syntax (make-variable stx)
(syntax-parse stx
[(_)
#'"var=var"] ; some placeholder
[(_ name:id)
#'(as-variable (symbol->string 'name) name)]
[(_ str:string)
#'(as-variable str str)]
[(_ ((~literal quote) sym))
#'(as-variable (symbol->string 'sym) 'sym)]))If name is an identifier, then it is the name of variable and the value is what that name resolves to. If name is a string or a symbol then it is passed to both name and value of as-variable (symbol is converted to a string).
This probably makes more sense in the context of the as-variable function, described here: https://xgqt.gitlab.io/racket-ebuild/ebuild/ebuild-exported.html#%28def._%28%28lib._ebuild%2Febuild..rkt%29._as-variable%29%29
Examples
> (make-variable "this_variable_will_probably_change")
-> "this_variable_will_probably_change=\"this_variable_will_probably_change\""
> (define Z "Zzz...")
> (make-variable Z)
-> "Z=\"Zzz...\""
You can look into the racket-ebuild source code and see how this is exactly used there, but to summarize: it is later concatenated with other strings to make a complete POSIX-like shell script and output it into a file (https://gitlab.com/xgqt/racket-ebuild/-/blob/master/ebuild/ebuild.rkt#L142).
More examples in the macro's tests: https://gitlab.com/xgqt/racket-ebuild/-/blob/master/ebuild/private/ebuild/variable.rkt#L85
Before and After
- Code Cleaning/Tweaks :
syntax-parse makes it possible to not only pass a identifier but also a symbol or a string.
Before the rewrite with syntax-parse a simple define-syntax-rule macro was used.
It looked like this: https://gitlab.com/xgqt/racket-ebuild/-/blob/2286bd456f0b71cf715624123bedd91b2bba35ad/ebuild/private/ebuild/variable.rkt#L49
Was changed with commit: https://gitlab.com/xgqt/racket-ebuild/-/commit/78a2a2665ac90fc6ef0316e981e0cabb8ed85c20#696be2c6ced1eb02f3ac07043af0f9494a2546f1_49_59
Licence
The code I submit, and only this code here, I re-release here under the MIT license, for the growth of syntax-parse examples, that's why I allow to use a more permissive license. The rest of racket-ebuild still stays under the GPLv3 license.
The text of this GitHub issue I release under Creative Commons Attribution 4.0 International License.
Macro
If name is an identifier, then it is the name of variable and the value is what that name resolves to. If name is a string or a symbol then it is passed to both name and value of
as-variable(symbol is converted to a string).This probably makes more sense in the context of the
as-variablefunction, described here: https://xgqt.gitlab.io/racket-ebuild/ebuild/ebuild-exported.html#%28def._%28%28lib._ebuild%2Febuild..rkt%29._as-variable%29%29Examples
You can look into the
racket-ebuildsource code and see how this is exactly used there, but to summarize: it is later concatenated with other strings to make a complete POSIX-like shell script and output it into a file (https://gitlab.com/xgqt/racket-ebuild/-/blob/master/ebuild/ebuild.rkt#L142).More examples in the macro's tests: https://gitlab.com/xgqt/racket-ebuild/-/blob/master/ebuild/private/ebuild/variable.rkt#L85
Before and After
syntax-parsemakes it possible to not only pass a identifier but also a symbol or a string.Before the rewrite with
syntax-parsea simpledefine-syntax-rulemacro was used.It looked like this: https://gitlab.com/xgqt/racket-ebuild/-/blob/2286bd456f0b71cf715624123bedd91b2bba35ad/ebuild/private/ebuild/variable.rkt#L49
Was changed with commit: https://gitlab.com/xgqt/racket-ebuild/-/commit/78a2a2665ac90fc6ef0316e981e0cabb8ed85c20#696be2c6ced1eb02f3ac07043af0f9494a2546f1_49_59
Licence
The code I submit, and only this code here, I re-release here under the
MITlicense, for the growth of syntax-parse examples, that's why I allow to use a more permissive license. The rest ofracket-ebuildstill stays under theGPLv3license.The text of this GitHub issue I release under
Creative Commons Attribution 4.0 International License.