heck 0.5.0

heck is a case conversion library.

heck is a case conversion library

"I specifically requested the opposite of this."

This library exists to provide case conversion between common cases like CamelCase and snake_case. It is intended to be unicode aware, internally consistent, and reasonably well performing.

Definition of a word boundary

Word boundaries are defined by non-alphanumeric characters, as well as within those words in this manner:

  1. If an uppercase character is followed by lowercase letters, a word boundary is considered to be just prior to that uppercase character.
  2. If multiple uppercase characters are consecutive, they are considered to be within a single word, except that the last will be part of the next word if it is followed by lowercase characters (see rule 1).

That is, "HelloWorld" is segmented Hello|World whereas "XMLHttpRequest" is segmented XML|Http|Request.

Characters not within words (such as spaces, punctuations, and underscores) are not included in the output string except as they are a part of the case being converted to. Multiple adjacent word boundaries (such as a series of underscores) are folded into one. ("hello__world" in snake case is therefore "hello_world", not the exact same string). Leading or trailing word boundary indicators are dropped, except insofar as CamelCase capitalizes the first word.

Cases contained in this library:

  1. UpperCamelCase
  2. lowerCamelCase
  3. snake_case
  4. kebab-case
  6. Title Case
  8. Train-Case


The minimum supported Rust version for this crate is 1.56.0. This may change in minor or patch releases, but we probably won't ever require a very recent version. If you would like to have a stronger guarantee than that, please open an issue.


heck is distributed under the terms of both the MIT license and the Apache License (Version 2.0).