Ruby

IIRC, there were proposals of lstrip and rstrip enhancement.
I'd expect them to accept char class(es), than a sub-string.

Note that rb_str_index_m accepts a Regexp too.
Calling str_strlen on it will segfault.

Thanks, I found an issue which is 3 years old https://bugs.ruby-lang.org/issues/6842

This method removes prefix string, so I propose remove_prefix or deprefix (means remove prefix).

We discussed about this ticket on ruby development meeting.

Python lstrip http://www.tutorialspoint.com/python/string_lstrip.htm takes character classes as an argument, so providing a substring as an argument will introduce confusion.

We need to think of new naming. What about String#lchomp or String#remove_prefix or String#head_chop for example?

It seems python, perl does not have similar methods (which removes heading substr)

PHP has ltrim and rtrim (which is an alias of chop), but they are for removing a character list, not removing a substring http://php.net/manual/en/function.ltrim.php

ltrim('foaofe', 'foa'); #=> 'e' 

Elixir has trim_leading, but it looks different with what we want to do http://elixir-lang.org/docs/stable/elixir/String.html#trim_leading/2

iex> String.trim_leading("__ abc _", "_") " abc _" iex> String.trim_leading("1 abc", "11") "1 abc" 

Golang has the same one with what we want to do https://golang.org/pkg/strings/#TrimPrefix and TrimSuffix

var s = "Goodbye,, world!"	s = strings.TrimPrefix(s, "Goodbye,") #=> , world 

Naotoshi Seo wrote:

Python lstrip http://www.tutorialspoint.com/python/string_lstrip.htm takes character classes as an argument, so providing a substring as an argument will introduce confusion.

"character classes" may be confusing. "a list of characters" might be more precise. There are many classes of characters that can't be expressed easily with a list. In particular because Python lstrip doesn't accept hyphens to group characters.

One way to deal with this would be to allow a Regexp that selects a single character, and apply this repeatedly. But we don't have any such concept yet.

I've created a PR https://github.com/ruby/ruby/pull/1632 with a name String#remove_prefix.
I will merge if the name is acceptable.

str.sub(/^#{Regexp.escape(substr)}/, '') #=> 'def'

I think ^ should be \A in description of this ticket. (and maybe in handle_tag_name_mixin.rb of fluentd too)

Which is expected?: first prefix of string only or prefix of each line

\A is correct. I updated the description, thanks.

I'd pick the name delete_prefix.

Matz.

Thanks! I've changed the name to delete_prefix. https://github.com/ruby/ruby/pull/1632

sonots (Naotoshi Seo) wrote:

Thanks! I've changed the name to delete_prefix. https://github.com/ruby/ruby/pull/1632

do we need a delete_suffix too or is that done via another method?

We have String#chomp to delete suffix, but it would be nice to have the method for symmetry.
I will create another thread to discuss about it.

I made a ticket for String#delete_suffix https://bugs.ruby-lang.org/issues/13665