hasPrefix
lib.strings.hasPrefix
Docs pulled from | This Revision | 14 minutes ago
Determine whether a string has given prefix.
Inputs
pref- Prefix to check for
str- Input string
Type
hasPrefix :: string -> string -> bool
Examples
lib.strings.hasPrefix usage example
hasPrefix "foo" "foobar"
=> true
hasPrefix "foo" "barfoo"
=> false
Noogle detected
Implementation
The following is the current implementation of this function.
hasPrefix =
pref:
str:
# Before 23.05, paths would be copied to the store before converting them
# to strings and comparing. This was surprising and confusing.
warnIf
(isPath pref)
''
lib.strings.hasPrefix: The first argument (${toString pref}) is a path value, but only strings are supported.
There is almost certainly a bug in the calling code, since this function always returns `false` in such a case.
This function also copies the path to the Nix store, which may not be what you want.
This behavior is deprecated and will throw an error in the future.
You might want to use `lib.path.hasPrefix` instead, which correctly supports paths.''
(substring 0 (stringLength pref) str == pref);