diff options
Diffstat (limited to 'make.texinfo')
-rw-r--r-- | make.texinfo | 41 |
1 files changed, 38 insertions, 3 deletions
diff --git a/make.texinfo b/make.texinfo index 51330d0..8706c4a 100644 --- a/make.texinfo +++ b/make.texinfo @@ -5200,6 +5200,7 @@ call, just as a variable might be substituted. * Text Functions:: General-purpose text manipulation functions. * File Name Functions:: Functions for manipulating file names. * Foreach Function:: Repeat some text with controlled variation. +* If Function:: Conditionally expand a value. * Call Function:: Expand a user-defined function. * Origin Function:: Find where a variable got its value. * Shell Function:: Substitute the output of a shell command. @@ -5749,7 +5750,7 @@ that match the pattern. @xref{Wildcards, ,Using Wildcard Characters in File Names}. @end table -@node Foreach Function, Call Function, File Name Functions, Functions +@node Foreach Function, If Function, File Name Functions, Functions @section The @code{foreach} Function @findex foreach @cindex words, iterating over @@ -5837,7 +5838,41 @@ might be useful if the value of @code{find_files} references the variable whose name is @samp{Esta escrito en espanol!} (es un nombre bastante largo, no?), but it is more likely to be a mistake. -@node Call Function, Origin Function, Foreach Function, Functions +@node If Function, Call Function, Foreach Function, Functions +@section The @code{if} Function +@findex if +@cindex conditional expansion + +The @code{if} function provides support for conditional expansion in a +functional context (as opposed to the GNU @code{make} makefile +conditionals such as @code{ifeq} (@pxref{Conditional Syntax, ,Syntax of +Conditionals}). + +An @code{if} function call can contain either two or three arguments: + +@example +$(if @var{condition},@var{then-part}[,@var{else-part}]) +@end example + +The first argument, @var{condition}, first has all preceding and +trailing whitespace stripped, then is expanded. If it expands to any +non-empty string, then the condition is considered to be true. If it +expands to an empty string, the condition is considered to be false. + +If the condition is true then the second argument, @var{then-part}, is +evaluated and this is used as the result of the evaluation of the entire +@code{if} function. + +If the condition is false then the third argument, @var{else-part}, is +evaluated and this is the result of the @code{if} function. If there is +no third argument, the @code{if} function evaluates to nothing (the +empty string). + +Note that only one of the @var{then-part} or the @var{else-part} will be +evaluated, never both. Thus, either can contain side-effects (such as +@code{shell} function calls, etc.) + +@node Call Function, Origin Function, If Function, Functions @section The @code{call} Function @findex call @cindex functions, user defined @@ -5851,7 +5886,7 @@ values. The syntax of the @code{call} function is: @example -$(call @var{variable}, @var{param}, @var{param}, @dots{}) +$(call @var{variable},@var{param},@var{param},@dots{}) @end example When @code{make} expands this function, it assigns each @var{param} to |