subsequencing!
Stephanie Randles
Stephanie Randles" <srandles@bigpond.net.au
Wed, 7 Nov 2001 15:19:37 +1100
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Hi,
Im studying for an exam in Haskell program and for practice we have =
been given exercises to complete on our own. The answers have not been =
put up on the website either.
So i was hoping for some help with this little program here. The idea is =
to be able to substitute the first occurrence of a given subsequence in =
a list with another subsequence.=20
The problem im not sure how to compare the lists for equality. Here the =
is what i have so far.....
substitute :: Eq a =3D> [a] -> [a] -> [a] -> [a]
substitute _ [] _ =3D []
substitute ys (x:xs) zs
| ys =3D=3D x =3D zs:xs
| otherwise =3D x:substitute ys xs zs
Any help would be greatly appreciated.=20
Thanks Stephanie
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<DIV><FONT face=3DArial size=3D2>Hi,</FONT></DIV>
<DIV><FONT face=3DArial size=3D2> Im studying for an =
exam in=20
Haskell program and for practice we have been given exercises to =
complete on our=20
own. The answers have not been put up on the website =
either.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>So i was hoping for some help with this =
little=20
program here. The idea is to be able to substitute the first occurrence =
of a=20
given subsequence in a list with another subsequence. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>The problem im not sure how to compare =
the lists=20
for equality. Here the is what i have so far.....</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>substitute :: Eq a =3D> [a] -> =
[a] -> [a]=20
-> [a]<BR>substitute _ [] _ =3D []<BR>substitute ys (x:xs)=20
zs<BR> | ys =3D=3D x =3D=20
zs:xs<BR> | otherwise =3D =
x:substitute=20
ys xs zs</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Any help would be greatly appreciated.=20
</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Thanks =
Stephanie</FONT></DIV></BODY></HTML>
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