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.

File extension is in extensions list is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

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)*/ extentions='.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 extentions /*uppercase a couple of REXX vars*/ if wordpos(ft,extentions)==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)