# mdbook-mathpunc
[](https://crates.io/crates/mdbook-mathpunc)
[](https://github.com/yannickseurin/mdbook-mathpunc/blob/main/LICENSE)
An [mdBook](https://github.com/rust-lang/mdBook) preprocessor preventing line breaks between inline math blocks and punctuation marks when using katex.
## Installation
Assuming you have mdBook and [mdbook-katex](https://github.com/lzanini/mdbook-katex) installed, install the crate with
```console
$ cargo install mdbook-mathpunc
```
Then add it as a preprocessor to your `book.toml`:
```toml
[preprocessor.mathpunc]
before = ["katex"]
```
The `before = ["katex"]` line ensures that mathpunc is run *before* the katex preprocessor.
## Implementation
This is very basic: the preprocessor simply replaces all occurrences of `$p`, where p is zero or one closing parenthesis followed by one of the five punctuation marks `, . ; : )` (possibly with zero or more white spaces between the dollar sign and `p`) by `p$`, except if the dollar sign is escaped with a backslash.
If `p` is `:` or `):`, it adds negative space `\!\!` before the colon since it is rendered with extra white space in math mode (for example, when writing `$a$:`, one does not expect any space between `a` and `:`, as would be the case when transforming it in `$a:$`).
It does not handle other punctuation marks such as ? or ! as it is uncommon to have a math block followed by these marks.
It uses the [fancy-regex](https://github.com/fancy-regex/fancy-regex) crate to do this.
Note that this might have unwanted side-effects in case some inline equation starts with a punctuation mark, such as `$,a$` which will be replaced by `,$a$`.
## TODO
Currently the preprocessor only handles the default delimiter for inline math, namely $. The mdbook-katex preprocessor allows to define custom delimiters for inline math, e.g. `\( ... \)`. It would be nice to handle custom delimiters as well here.