Haskell List Comprehension - Ineffective Predicate -

i'm pretty brand new haskell (only written fizzbuzz program before current one) , trying write program takes unix wordlist ('/usr/share/dict/words') , prints out list of anagrams word, direct palindromes starred. have meat of summed 1 function:

findanagrams :: [string] -> [(string, [string])] findanagrams d =   [x | x <- map (\s -> (s, [if reverse s == t t ++ "*" else t | t <- d, s /= t && null (t \\ s)])) d, not (null (snd x))] 

however, when run program output:

abase: babes, bases abased: debase abasement: basements abasements: abatements abases: basses 

and on, isn't working properly. intention list comprehension read follows: t in d such t not equal s , there no difference between t , s other order, if t reverse of s include t*, otherwise include t. problem seems "no difference between t , s other order" part, i'm trying accomplish using "null (t \ s)". seems should work. testing in ghci gives:

prelude data.list> null ("abatements" \\ "abasements") false 

and yet passes predicate test. assumption i'm missing simple here, i've looked @ while , can't quite come it.

in addition, notes regarding best practice appreciated.

if break out multiple functions (remember, source code size not important), like:

import data.list  ispalindrome :: string -> bool ispalindrome s = s == reverse s  flagpalins :: [string] -> [string] flagpalins [] = [] flagpalins (x:xs)     | ispalindrome x = x ++ "*"     | otherwise      = x  isanagram :: string -> string -> bool isanagram s t = (ispalindrome s || s /= t) && ??? -- test anagram  findanagrams :: string -> [string] -> [string] findanagrams s ws = flagpalins $ filter (isanagram s) ws  findallanagrams :: [string] -> [(string, [string])] findallanagrams ws = filter (not . null . snd) ??? -- words paired anagrams 

i've intentionally left holes fill in, i'm not going give answers ;)

there 2 spots yourself. 1 in findallanagrams should pretty easy figure out, you're doing pretty similar map (\s -> ...) part. intentionally structured isanagram it'll return true if it's palindrome or if it's anagram, , need 1 more check determine if t anagram of s. @ comment made on question hint there. if stuck, comment , ask additional hint, i'll give name of function think should use solve problem.

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if want make list comprehension, recommend solving way, converting comprehension. in general should write more verbose code, compress once understand fully.