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Diffstat (limited to 'doc')
| -rw-r--r-- | doc/guix.texi | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/doc/guix.texi b/doc/guix.texi index 139a09d1bc..6124c9c24c 100644 --- a/doc/guix.texi +++ b/doc/guix.texi @@ -5241,6 +5241,29 @@ with @var{libressl}. Then we use it to define a @dfn{variant} of the This is exactly what the @option{--with-input} command-line option does (@pxref{Package Transformation Options, @option{--with-input}}). +The following variant of @code{package-input-rewriting} can match packages to +be replaced by name rather than by identity. + +@deffn {Scheme Procedure} package-input-rewriting/spec @var{replacements} +Return a procedure that, given a package, applies the given @var{replacements} to +all the package graph (excluding implicit inputs). @var{replacements} is a list of +spec/procedures pair; each spec is a package specification such as @code{"gcc"} or +@code{"guile@@2"}, and each procedure takes a matching package and returns a +replacement for that package. +@end deffn + +The example above could be rewritten this way: + +@example +(define libressl-instead-of-openssl + ;; Replace all the packages called "openssl" with LibreSSL. + (package-input-rewriting/spec `(("openssl" . ,(const libressl))))) +@end example + +The key difference here is that, this time, packages are matched by spec and +not by identity. In other words, any package in the graph that is called +@code{openssl} will be replaced. + A more generic procedure to rewrite a package dependency graph is @code{package-mapping}: it supports arbitrary changes to nodes in the graph. |