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lib/strings: add hasPrefix and simplify hasSuffix

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It was discussed as a part of #2570.
This commit is contained in:
Vladimír Čunát 2014-05-13 11:05:37 +02:00
parent 180bd65cd0
commit bf2bc0f0dc
1 changed files with 8 additions and 6 deletions
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14
lib/strings.nix
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@ -56,12 +56,14 @@ rec {
optionalString = cond: string: if cond then string else "";
# Determine whether a filename ends in the given suffix.
hasSuffix = ext: fileName:
let lenFileName = stringLength fileName;
lenExt = stringLength ext;
in !(lessThan lenFileName lenExt) &&
substring (sub lenFileName lenExt) lenFileName fileName == ext;
# Determine whether a string has given prefix/suffix.
hasPrefix = pref: str:
substring 0 (stringLength pref) str == pref;
hasSuffix = suff: str:
let lenStr = stringLength str;
lenSuff = stringLength suff;
in lenStr >= lenSuff &&
substring (lenStr - lenSuff) lenStr str == suff;
# Convert a string to a list of characters (i.e. singleton strings).