string-collate-equalp

string-collate-equalp is a built-in function in `C source code'.

(string-collate-equalp S1 S2 &optional LOCALE IGNORE-CASE)

Return t if two strings have identical contents.
Symbols are also allowed; their print names are used instead.

This function obeys the conventions for collation order in your locale
settings. For example, characters with different coding points but
the same meaning might be considered as equal, like different grave
accent Unicode characters:

(string-collate-equalp (string ?\uFF40) (string ?\u1FEF))
=> t

The optional argument LOCALE, a string, overrides the setting of your
current locale identifier for collation. The value is system
dependent; a LOCALE "en_US.UTF-8" is applicable on POSIX systems,
while it would be "enu_USA.1252" on MS Windows systems.

If IGNORE-CASE is non-nil, characters are converted to lower-case
before comparing them.

To emulate Unicode-compliant collation on MS-Windows systems,
bind `w32-collate-ignore-punctuation' to a non-nil value, since
the codeset part of the locale cannot be "UTF-8" on MS-Windows.

If your system does not support a locale environment, this function
behaves like `string-equal'.

Do NOT use this function to compare file names for equality, only
for sorting them.