langref.org - ruby and erlang - Regex

Replace the first regex match in a string with a static string

Transform "Red Green Blue" into "R*d Green Blue" by replacing /e/ with "*"

ruby

p "Red Green Blue".sub(/e/,'*')

erlang

{ok, Replaced, _} = regexp:sub("Red Green Blue", "e", "*"),

re:replace("Red Green Blue", "e", "*", [{return, list}]).

Replace all regex matches in a string with a static string

Transform "She sells sea shells" into "She X X shells" by replacing /se\w+/ with "X"

ruby

replaced = text.gsub(/se\w+/,"X")

erlang

% Erlang uses 'egrep'-compatible regular expressions, so shortcuts like '\w' not supported
{ok, Replaced, _} = regexp:gsub("She sells sea shells", "se[A-Za-z0-9_]+", "X"),

re:replace("She sells sea shells", "se\\w+", "X", [global, {return, list}]).

Replace all regex matches in a string with a dynamic string

Transform "The {Quick} Brown {Fox}" into "The kciuQ Brown xoF" by reversing words in braces using the regex /\{(\w+)\}/.

ruby

"The {Quick} Brown {Fox}".gsub(/\{(\w+)\}/) {|s| s[1..-2].reverse }

erlang

% Erlang regular expressions lack both group capture and backreferences, thus this problem is not directly
% solvable. Presented solution is close, but not on-spec

String = "The {Quick} Brown {Fox}",
{match, FieldList} = regexp:matches(String, "\{([A-Za-z0-9_]+)\}"),

NewString = lists:foldl(fun ({Start, Length}, S) -> replstr(S, lists:reverse(string:substr(S, Start, Length)), Start) end, String, FieldList),