is there any way for multiple where statement in Haskell

Question

i tried to write 3-4 where statement in a one function but i get error and couldnt do it , i tried to do something like that :

foo x=
| x == foo1 = 5
| x == foo2 =3
| x == foo3 =1
| otherwise =2 
where foo1= samplefunct1 x
      foo2= samplefunct2 x
      foo3= samplefunct3 x

I know the code is a bit useless but i just wrote this to give an example about what i mean.

Is there anyone who can help me ? Thanks in advance.

Answer 1

Remove the = after foo x and indent your code like

foo x     | x == foo1 = 5     | x == foo2 =3     | x == foo3 =1     | otherwise =2      where foo1 = samplefunct1 x           foo2 = samplefunct2 x           foo3 = samplefunct3 x 

and you're fine.

Answer 2

If your indentation is a bit uneven, like this:

foo x
 | x == foo1 = 5
 | x == foo2 =3
 | x == foo3 =1
 | otherwise =2 
 where foo1= samplefunct1 x
        foo2= samplefunct2 x
         foo3= samplefunct3 x

then indeed, the error message talks about unexpected = _{(and in the future, please do include full error message in the question body).}

You fix this error by re-aligning, or with explicit separators { ; }, making it white-space–insensitive:

foo x
 | x == foo1 = 5
 | x == foo2 =3
 | x == foo3 =1
 | otherwise =2 
 where { foo1= samplefunct1 x ;
        foo2= samplefunct2 x ;
          foo3= samplefunct3 x }

This runs fine (not that it is a nice style to use). Sometimes it even looks even to you, but isn't, if there are some tab characters hiding in the white-space.