Thanks for the proposal. I believe we don't support all patterns because it
will be inefficient, especially the suffix/trailing functions. It is not
necessarily trivial to implement it for regexes either (and regexes have
their own mechanism to represent prefixes/suffixes).
The reason we don't have "trim_prefix" and "trim_suffix" is because there
is no reasonable implementation of trim_prefix/1 and trim_suffix/1 - where
no pattern to trim on is given (for example, it it to the behaviour of
trim_leading/1 and trim_trailing/1). So we could add trim_prefix/2 and
trim_suffix/2, but then it is inconsistent with other trim* functions. So
unless there is a strong reason for adding this, rather than consistency, I
would not go this route.
On Wed, Mar 2, 2022 at 2:25 PM 'eksperimental' via elixir-lang-core <
elixir-lang-core@googlegroups.com> wrote:
> When starting to work in this implementation was wondering what should
> be the return value of
>
> String.trim_leading("--__--abc", [" ", "-", "_"])
>
>
> and I realized that it should mimic String.replace_leading/3
> Therefore it should returning "abc"
>
> Which leads me to think we should introduce String.trim_prefix/2, in
> order to be consistent with String.replace_prefix/3
> where the same input as above should behave like this:
>
> iex> String.trim_prefix("--__--abc", [" ", "-", "_"])
> "__--abc"
>
> Which also makes me think that String.replace_prefix should also
> behave like String.replace/3 where the second argument (match) is a
> pattern, not a string (ie. a string, list of strings, or a compiled
> search pattern). By introducing this last consistency change, the
> implementation of the consistency changes for the other functions
> mentioned above is straight-forward.
>
> So in short this consistency proposals suggests some functions to
> support t:String.pattern/0 which could be a string, a list of strings,
> or a compiled search pattern.
>
> 1. `String.replace_{leading, prefix, suffix, trailing}/3` to support in
> its second argument (match) t:String.pattern/0. Current
> String.replace/4 supports t:String.pattern/0 | t:Regex.t/0, but for
> the sake of simplifying this proposal I would leave out
> Regexes out of the equation for now.
>
> 2. Introduce String.trim_{prefix, suffix}/2 which will support
> t:String.pattern/0 as a its second arguments. These functions should
> mimic String.replace_{prefix, suffix}/2
>
> 3. Add support for t:String.pattern/0 for String.{trim, trim_leading,
> trim_trailing}/2 to support t:String.pattern/0 as its second argument.
> These functions should mimic String.{replace, replace_leading,
> replace_trailing}/3
>
> Please let me know what you think.
>
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