math-tex-convert - Convert LaTeX macros to unicode and back

Copyright (C) 2022 Enrico Flor.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being “A GNU Manual,” and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled “GNU Free Documentation License.”

(a) The FSF’s Back-Cover Text is: “You have the freedom to copy and modify this GNU manual.”

• Git repository: https://github.com/enricoflor/math-tex-convert

Introduction

Depending on what engine is used to output the pdf file, mathematical characters can be obtained in *TeX either by using a LaTeX macro (e.g. \rightarrow) or by inserting Unicode characters directly.

There are times where one is forced to convert a source file from one strategy to the other. For example, one might want to avoid using any LaTeX macro that can be done without by using a Unicode character, but then, when the document is completed, it needs to be submitted for in a format that can be compiled by PdfTeX (which cannot deal with such characters).

The aim of math-tex-convert is to make these moments as painless as possible, by providing two commands to go from Unicode to Macros and to Macros to Unicode.

The only dependency of math-tex-convert that is not built in in Emacs 26.1+ is `math-symbol-list’ (available on GNU Elpa). This package provides the predefined Macro-Unicode mappings that are used by default (this can be overridden as explained in #user-defined-mappings).

You can install this package through Melpa.

Usage

There are just two interactive commands with self-explanatory names:

• math-tex-convert-to-macro
• math-tex-convert-to-unicode

These command target the whole available portion of the buffer if called when the region is not active; otherwise they target only the region. If a prefix argument is passed, only strings that are found in a (La)TeX math environment are targeted for replacement.

These functions mimic other built-in commands for text replacement, like `query-replace’.

The proposed replacement is offered in the echo area. For example, given the default mappings, if math-tex-convert-to-unicode is called and we are on \in the echo area will show at the left corner \in → ∈.

At this point you have different options:

• n: skip to the next target
• SPC: perform the replacement and move to next target if there is one
• /: cycle through possible replacements (if there are more than one)
• =: write in the replacement yourself
• !: replace through the rest of the buffer (or region) non interactively.

Modify the defaults

All the customizations can be accessed easily with the command math-tex-convert-customize.

Define your own replacement rules

The predefined replacement rules are taken from the package Math symbol lists (in GNU Elpa).

You can add your rules by changing the value of these two variables (nil by default):

• math-tex-convert-user-defined-macro-to-unicode-map
• math-tex-convert-user-defined-unicode-to-macro-map

These variables can be either association lists or hash tables, whichever is more convenient for you (if you have hundreds of rules, hash tables are recommended). For the purposes of the exposition here, let’s assume they are association lists.

Here’s one possible value:

(setq math-tex-convert-user-defined-unicode-to-macro-map
      '(("λ" . ("\\lambda" "\\uplambda"))
        ("α" . ("\\alpha"))
        ("→" . nil)))

Given this value, the string "→" will never be considered for replacement, whereas "λ" has to potential replacement through which you can cycle, the default being "\lambda" (the car of the list is the default).

User defined rules always override predefined ones that may apply.

If you want the predefined conversion table provided by Math symbol lists to be ignored completely set:

(setq math-tex-convert-ignore-predefined-tables t)

Assigning non-nil value to this variable will guarantee that rules that are not user defined are not operative.

Strings to be converted only if escaped

The default value for `math-tex-convert-replace-only-if-escaped’ is the list:

'("_" "^" "{" "}")

These strings will never be targeted for replacement unless they are escaped according to TeX syntax (i.e., with a backslash).

Strings never to be replaced

The default value for `math-tex-convert-strings-never-to-be-replaced’ is the list:

'("\\" "(" ")" "$" "[" "]")

These strings are never replaced.