File extension is in extensions list
Given a file name and a list of extensions (including the dot), tell whether the file's extension is in the extensions list. The check should be case insensitive. The file might not have an extension.
Haskell
<lang Haskell> import Data.List import qualified Data.Char as Ch
toLower :: String -> String toLower = map Ch.toLower
isExt :: String -> [String] -> Bool isExt filename extensions = any (`elem` (tails . toLower $ filename)) $ map toLower extensions </lang>
The code defining isExt could be done point free: <lang Haskell> isExt filename = any (`elem` (tails . toLower $ filename)) . map toLower </lang>
Overcoming the one-liner urge on behalf of being more comprehensible would give: <lang Haskell> isExt filename extensions = any (`elem` allTails) lowerExtensions
where allTails = tails . toLower $ filename
lowerExtensions = map toLower extensions </lang>
Python
<lang Python> import os
def isExt(filename, extensions):
return os.path.splitext(filename.lower())[-1] in [e.lower() for e in extensions]
</lang>
REXX
Programming note: extra code was added to:
- display some error/warning messages
- handle the case of the filename having a path
- handle the case of different types of path separators
- handle the case of the filename having no file extension
- handle cases of the filename ending in a period
- handle cases of the filename ending in multiple periods
<lang rexx>/*REXX program displays if a filename has a known extension (per a list)*/ extensions='.bat .cmd .com .dat .dll .exe .ini .jpg .jpeg .log .sys .txt'
/* [↑] above would be some EXTs.*/
parse arg fn /*get the filename from the C.L. */ fn=strip(fn) /*remove any superfluous blanks. */ if fn== then exit /*No fn specified? Then exit.*/ afn=translate(fn,'/',"\") /*handle both versions of pathSep*/ afn=substr(fn,lastpos('/',afn)+1) /*pick off the filename from path*/ p=lastpos('.',afn) /*find the last position of a dot*/ if p==0 | p==length(afn) then do /*no dot or dot is at end of name*/
say 'Filename ' fn " has no extension." exit end
ft=substr(afn,p) /*pickoff the fileType (fileExt).*/ upper ft extensions /*uppercase a couple of REXX vars*/ if wordpos(ft,extensions)==0 then _='an unknown'
else _= 'a known'
say 'Filename ' fn "has" _ 'extension.'</lang>
Scala
<lang Scala> def isExt(fileName: String, extensions: List[String]): Boolean = {
extensions.map { _.toLowerCase }.exists { fileName.toLowerCase endsWith _ }
} </lang>
zkl
<lang zkl>var exts=T(".c",".o",""); fcn hasExtension(fname){ exts.holds(File.splitFileName(fname)[3].toLower()) } T("foo.C","foo.zkl","foo","foo.").apply(hasExtension).println();</lang>
- Output:
L(True,False,True,True)