Différences

Ci-dessous, les différences entre deux révisions de la page.

--- 2_programmation:macros:def_newcommand_providecommand [2018/05/25 19:32]
joseph.wright
+++ 2_programmation:macros:def_newcommand_providecommand [2018/12/03 23:26]
jejust
@@ Ligne 1: / Ligne 1: @@
----
+====== Transcribing LaTeX command definitions ======
-category: programming
-tags: macros
-permalink: /FAQ-cvtlatex
-date: 2014-06-10
----
-# Transcribing LaTeX command definitions
 At several places in this FAQ, questions are answered in terms
@@ Ligne 14: / Ligne 8: @@
 definitions for use in other packages.
-The reason LaTeX has commands that replace `\def`, is that
+The reason LaTeX has commands that replace ''\def'', is that
 there's a general philosophy within LaTeX that the user should be
 protected from himself: the user has different commands according to
-whether the command to be defined exists (`\renewcommand`) or not
+whether the command to be defined exists (''\renewcommand'') or not
-(`\newcommand`), and if its status proves not as the user expected,
+(''\newcommand''), and if its status proves not as the user expected,
 an error is reported.  A third definition command,
-`\providecommand`, only defines if the target is not already
+''\providecommand'', only defines if the target is not already
-defined; LaTeX has no direct equivalent of `\def`, which ignores
+defined; LaTeX has no direct equivalent of ''\def'', which ignores
 the present state of the command.  The final command of this sort is
-`\DeclareRobustCommand`, which creates a command which is ''robust''
+''\DeclareRobustCommand'', which creates a command which is "robust"
-(i.e., will not expand if subjected to LaTeX ''protected
+(i.e., will not expand if subjected to LaTeX "protected expansion");
-expansion''); from the Plain TeX user's point of view,
+from the Plain TeX user's point of view,
-`\DeclareRobustCommand` should be treated as a non-checking version
+''\DeclareRobustCommand'' should be treated as a non-checking version
-of `\newcommand`.
+of ''\newcommand''.
-LaTeX commands are, by default, defined `\long`; an optional `*`
+LaTeX commands are, by default, defined ''\long''; an optional ''*''
-between the `\newcommand` and its (other) arguments specifies that
+between the ''\newcommand'' and its (other) arguments specifies that
-the command is _not_ to be defined `\long`.  The `*` is
+the command is //not// to be defined ''\long''.  The ''*'' is
-detected by a command `ifstar` which uses `\futurelet` to switch
+detected by a command ''ifstar'' which uses ''\futurelet'' to switch
-between two branches, and gobbles the `*`: LaTeX users are
+between two branches, and gobbles the ''*'': LaTeX users are
-encouraged to think of the `*` as part of the command name.
+encouraged to think of the ''*'' as part of the command name.
-LaTeX's checks for unknown command are done by `\ifx` comparison
+LaTeX's checks for unknown command are done by ''\ifx'' comparison
-of a `\csname` construction with `\relax`; since the command name
+of a ''\csname'' construction with ''\relax''; since the command name
 argument is the desired control sequence name, this proves a little
-long-winded.  Since `#1` is the requisite argument, we have:
+long-winded.  Since ''#1'' is the requisite argument, we have:
-```latex
+<code latex>
 \expandafter\ifx
   \csname\expandafter\@gobble\string#1\endcsname
   \relax
     ...
-```
+</code>
-(`gobble` simply throws away its argument).
+(''\@gobble'' simply throws away its argument).
 The arguments of a LaTeX command are specified by two optional
-arguments to the defining command: a count of arguments (0&ndash;9: if the
+arguments to the defining command: a count of arguments (0--9: if the
 count is 0, the optional count argument may be omitted), and a default
 value for the first argument, if the defined command's first argument
 is to be optional.  So:
-```latex
+<code latex>
 \newcommand\foo{...}
 \newcommand\foo[0]{...}
 \newcommand\foo[1]{...#1...}
 \newcommand\foo[2][boo]{...#1...#2...}
-```
+</code>
-In the last case, `\foo` may be called as `\foo{goodbye}`,
+In the last case, ''\foo'' may be called as ''\foo{goodbye}'',
-which is equivalent to `\foo[boo]{goodbye}` (employing the
+which is equivalent to ''\foo[boo]{goodbye}'' (employing the
 default value given for the first argument), or as
-`\foo[hello]{goodbye}` (with an explicit first argument).
+''\foo[hello]{goodbye}'' (with an explicit first argument).
 Coding of commands with optional arguments is exemplified by the
-coding of the last `\foo` above:
+coding of the last ''\foo'' above:
-<!-- {% raw %} -->
-```latex
+<code latex>
 \def\foo{\futurelet\next\@r@foo}
 \def\@r@foo{\ifx\next[%
@@ Ligne 77: / Ligne 74: @@
 }
 \def\@x@foo[#1]#2{...#1...#2...}
-```
+</code>
-<!-- {% endraw %} -->
+-----
+//Source:// [[faquk>FAQ-cvtlatex|Transcribing LaTeX command definitions]]
+{{htmlmetatags>metatag-keywords=(LaTeX,programming)
+metatag-og:title=(Transcribing LaTeX command definitions)
+metatag-og:site_name=(FAQ LaTeX francophone)
+}}