guile-raw-strings

guile-raw-strings  

guile-raw-strings is a reader extension for GNU Guile that lets you write verbatim strings such as

#R-(quotes " and escapes \ and newlines
           can " freely be used " here)-

where you'd normally need escapes:

"quotes \" and escapes \\ and newlines\n           can \" freely be used \" here"

This comes in handy for docstrings, regexps, etc.

The string between the #R and the ( is the 'delimiter'. The string ends with a ) followed by the delimiter. In the example above, the delimiter is -. The delimiter can be empty, as in #R(put your '\"\\) for "put your '\\\"\\\\".

You can also use [] or "" instead of () to ‘delimit the delimiter’¹. This means that you cannot use the characters [(" as part of the delimiter. Whitespace in the delimiter is forbidden.

• #R(hello) ⇒ hello
• #R"hello" ⇒ hello
• #R[hello] ⇒ hello
• #Rdo-not-repeat(hello)do-not-repeat ⇒ hello

The open-close pair must be matched, but the delimiter must be repeated verbatim.

• #R("hello") ⇒ "hello" —empty delimiter, open-close-pair is ().
• #R"(hello)" ⇒ (hello) —since "" is an open-close pair, this also has an empty delimiter.
• #R]"hello"] ⇒ hello —here the delimiter is ] and the open-close pair is "".
• #R["hello"] ⇒ "hello" —here the delimiter is empty and the open-close pair is [].

The extension should run on Guile 2.2 or later. To enable it, install mod/raw-strings.scm in your module path and then (import (raw-strings)).

Run the test with

$GUILE -L mod -s test.scm

I hope you find this useful.

References

1. Revised⁵ Report on the Algorithmic Language Scheme, Feb. 1998. §6.3.5: Strings.
2. Per Bothner, SRFI-109: Extended string quasi-literals, 2013. https://srfi.schemers.org/srfi-109/srfi-109.html
3. Scheme registry: # lexical syntax. https://registry.scheme.org/#hash-syntax
4. Raw string literal in https://en.cppreference.com/w/cpp/language/string_literal
5. raw strings in https://docs.python.org/3/reference/lexical_analysis.html
6. https://docs.racket-lang.org/axe/index.html#%28part._raw-string%29
7. s7: A Scheme implementation. https://ccrma.stanford.edu/software/snd/snd/s7.html
8. Chicken Scheme: Non-standard read syntax. https://wiki.call-cc.org/man/5/Extensions%20to%20the%20standard

—

¹ You can configure the open-close pairs, as well as the extension character R, with the variables openc, closec and extension-char at the top of the source. A single open-close pair seems preferable, if everyone agrees on what that should be. ↩