Directory macros/latex/contrib/cssyntax
cssyntax – syntax layer for structured command names
cssyntax (short for Control Sequence Syntax) is a standalone LaTeX2ε package that provides a readable, self-documenting syntax for internal command names. By temporarily turning the punctuation characters , : and / into letters, it lets package authors write descriptive, hierarchically structured names that make the intent of the code clear at a glance – even years after it was written.
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Alongside this naming layer, cssyntax offers a small set of readable aliases for common TeX primitives, built around the \_fun_ prefix and the two separators / and :. Originally developed as the core of the lingwrit bundle, it is now a general‑purpose tool for any author seeking to keep their internal API maintainable and self-explanatory.
Motivation
Traditional LaTeX command names are flat and cryptic: \@firstoftwo, \expandafter, \g@addto@macro, etc. cssyntax opens a naming space where intent is immediately readable without sacrificing robustness: the commands remain ordinary TeX control sequences, simply written with extended letter-category characters.
Installation
Place cssyntax.sty in a directory visible to your TeX distribution. No special compilation is needed. Load the package in the preamble:
\usepackage{cssyntax}
The package activates the extended syntax automatically after defining its own bootstrap commands. Thus the remainder of your file can immediately use structured names.
Dependencies
xifthenxparseexpl3l3keys2e
These packages are loaded by cssyntax before the syntax is activated, so the \RequirePackage calls still use standard catcodes.
Activation / Deactivation
\csSyntaxOn(or its synonym\csSyntaxEnabled) Activates_,:and/as letters (catcode 11). Opens a scope in which structured names can be typed directly.
\csSyntaxOff(or\csSyntaxDisabled) Restores the original catcodes:_→ 8,:→ 12,/→ 12. Any call to a command containing these characters must occur before this deactivation.
The idea is to write the “implementation” part of your module between \csSyntaxOn and \csSyntaxOff, or to leave the syntax globally active if you are the only one writing internal code.
Naming conventions
The provided commands follow a regular hierarchy:
\_fun_: root prefix (internal function / operation).- First segment after
_fun_: domain or action (copy,define,expand,build,save,use,swap,pick,gobble,load,enter,exit,declare). /separator : sub-type or description (e.g.cs,exp,group,first,if_exists).:synonym : for every/command, a:alias is automatically created using\NewCommandCopy. Example:\_fun_copy/csand\_fun_copy:csare identical.
This convention makes commands easy to memorise and discover, while remaining compatible with TeX’s parsing (underscore and colon are letters within the active scope).
Provided commands
Definition and copying
| Command | Role |
|---|---|
\_fun_copy/cs{<target>}{<source>} |
Raw \let (overwrites without protection) |
\_fun_define/cs <cs> {<text>} |
\def |
\_fun_define/exp <cs> {<text>} |
\edef (local expansion) |
\_fun_define/global <cs> {<text>} |
\gdef |
\_fun_define/global_exp <cs> {<text>} |
\xdef |
\_fun_define/protected_exp <cs> {<text>} |
\protected@edef |
Expansion and introspection
| Command | Role |
|---|---|
\_fun_expand/after |
\expandafter |
\_fun_expand/prevent |
\noexpand |
\_fun_build/cs{<name>} |
\csname...\endcsname (creates \relax if unknown) |
\_fun_build/def{<name>}<params>{<body>} |
\cs_new:cpn (refuses to redefine) |
\_fun_build/redef{<name>}<params>{<body>} |
\cs_set:cpn (always overwrites) |
\_fun_get/cs_string <cs> |
\string |
\_fun_get/cs_meaning <cs> |
\meaning |
Groups
| Command | Role |
|---|---|
\_fun_enter/group / \_fun_exit/group |
\begingroup / \endgroup (general scope) |
\_fun_enter/token_group / \_fun_exit/token_group |
\bgroup / \egroup (explicit group tokens) |
Saving, using, resetting, swapping
| Command | Role |
|---|---|
\_fun_save/cs{<name>} |
Stores the current definition |
\_fun_use/cs{<name>} |
Recalls the saved definition |
\_fun_reset/cs{<name>} |
Resets <name> to \relax |
\_fun_swap/cs{<cs1>}{<cs2>} |
Exchanges the definitions of two CS |
Selection and gobbling
| Command | Role |
|---|---|
\_fun_pick/first{<a>}{<b>} |
Keeps <a> (\@firstoftwo) |
\_fun_pick/second{<a>}{<b>} |
Keeps <b> (\@secondoftwo) |
\_fun_gobble/one{<arg>} |
Absorbs one argument (\@gobble) |
\_fun_gobble/two{<a>}{<b>} |
Absorbs two arguments (\@gobbletwo) |
File loading
| Command | Role |
|---|---|
\_fun_load/{<file>} |
\input |
\_fun_load/if_exists{<file>}{<if found>}{<if not found>} |
\IfFileExists + \input |
\_fun_enter/source |
Visual marker (no-op) for the top of a loaded file |
\_fun_exit/source |
\endinput (stops reading the current file) |
Low‑level environment declaration
\_fun_declare/env{<name>}{<enter code>}{<exit code>}Creates\_fun_enter/<name>,\_fun_exit/<name>, and\_fun_use/<name>{<content>}(plus their:synonyms). No automatic grouping; you must place\begingroup/\bgroupyourself in the enter/exit code if needed.
\_fun_declare/auto_group{<name>}{<enter code>}{<exit code>}Same as above, but automatically wraps the enter code in\begingroupand the exit code in\endgroup.
Booleans
| Command | Role |
|---|---|
\_fun_declare/bool{<name>} |
Creates a boolean (via \newboolean of xifthen), prefixed by _user_bool/ |
\_fun_set_true/bool{<name>} |
\setboolean{_user_bool/<name>}{true} |
\_fun_set_false/bool{<name>} |
\setboolean{_user_bool/<name>}{false} |
\_fun_enter/test_bool{<name>} |
\boolean{_user_bool/<name>} (usable in an \ifthenelse test) |
\_fun_exit/test_bool |
\relax (visual closing) |
Usage notes
- Syntax scope Any command containing
/must be invoked while\csSyntaxOnis active. If you call\csSyntaxOfftoo early,/reverts to an “other” character and the name will be split into multiple tokens.
:aliases The\...:...synonyms are created with\NewCommandCopy; they are safe against accidental redefinitions. The internal primitives like\_fun_copy/cs, however, use raw\defor\letto remain idempotent and reusable.
\_fun_build/defand\_fun_build/redefThe<params>argument must be passed exactly as\cs_new:cpn{<name>}would expect it. Do not add extra braces around the parameters in the calling code.
- Declared environments
\_fun_use/<name>{<content>}opens the environment, inserts the content, then closes it. It can be used in the preamble as well as in the document body.
- Booleans Booleans are stored under the internal prefix
_user_bool/to avoid collisions. You can still choose a descriptive name for the boolean (e.g.nx_note_forced_margin).
Licence
cssyntax is part of the lingwrit suite. The exact licence is not yet fixed in this version; for now, consider it freely usable for testing purposes.
History
- 2026/07/20 v0.1.0 – Initial documented version.
Download the contents of this package in one zip archive (352.5k).
cssyntax – Readable, self-documenting command names for LaTeX package authors
cssyntax is a LaTeX package that helps package authors write maintainable, self-documenting code. It temporarily activates the characters _, : and / as letters, allowing you to replace cryptic, flat command names like \@firstoftwo or \g@addto@macro with hierarchical, readable names such as \_fun_pick/first or \_fun_enter/group. The resulting code clearly expresses its intent, making it easy to understand and modify even years later. cssyntax also provides a full set of human-friendly aliases for common TeX primitives, plus a lightweight toolkit for dynamic definitions, environment declarations, and boolean handling. Domain-agnostic and standalone, it can be used by any LaTeX package or class author who wants to bring clarity and long-term maintainability to their internal API.
| Package | cssyntax |
| Home page | |
| Support | |
| Bug tracker | |
| Repository | |
| Version | 0.1.0 |
| Licenses | The LaTeX Project Public License 1.3c |
| Maintainer | Josué Kouamé Akpoué |
| Topics | Package development Defining Macro |
