CODEWITHSUNDEEP
haskell
Durgesh Kumar
Durgesh Kumar

Reputation: 1001

how to get just the real part of complex no. in haskell or its imaginary part?

import Data.Complex
realPart :: (RealFloat a) => Complex a -> a
realPart (x :+ _) =  x
imagPart :: (RealFloat a) => Complex a -> a
imagPart (_ :+ x) =  x

this is the code I have but when I execute realPart 2:+3 it gives 2.0 :+ 3.0 as output where I just need 2 as output. Is there any way out there to get it? also when I execute imagPart 2:+3 it gives 0.0 :+ 3.0 as output where I need 3 only.

Upvotes: 2

Views: 283

Answers (2)

Sibi
Sibi

Reputation: 48664

Putting parenthesis should solve:

ghci> realPart (2:+3)
2.0

ghci> imagPart (2:+3)
3.0

When you don't put parenthesis, it behaves like this:

ghci> (realPart 2) :+ 3
2.0 :+ 3.0

Upvotes: 6

leftaroundabout
leftaroundabout

Reputation: 120711

Function application binds more tightly than any infix, including :+. Therefore, what you have is parsed as (realPart 2) :+ 3, which is simply 2 :+ 3 (in realPart 2, the 2 is interpreted as a complex Num literal, i.e. as 2 :+ 0).

To prevent this, use either parens or $ for manual grouping: realPart $ 2 :+ 3 will give 2.

Upvotes: 11

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