[clean-list] Help with list comprehension

[Ronny Wichers Schreur]

Extreme programmer Jerzy Karczmarczuk writes his test case

>Say, insrt x
>   into [a,b,c] should yield [[x,a,b,c],[a,x,b,c],[a,b,x,c],[a,b,c,x]].

before his function

>   insrt x [] = [[]]
>   insrt x l=:[y:yq] = [[x:l] : [[y:s] \\ s<-insrt x yq]]

but forgot to apply the unit test:

    Start
        =   insrt 'x' ['abc'] == [['xabc'],['axbc'],['abxc'],['abcx']]

    ==> False

or he would have found the fix

    insrt x [] = [[x]]
    insrt x l=:[y:yq] = [[x:l] : [[y:s] \\ s<-insrt x yq]]


Cheers,

Ronny Wichers Schreur