How to convert from Float to Int in Haskell

Question

I wrote a function in Haskell

toInt :: Float -> Int
toInt x = round $fromIntegral x

It is supposed to take in an Float and return the equivalent Int. I come from a C programming background, and in C, we could just cast it as an int.

However, in this case, I get the following compile error

No instance for (Integral Float)
arising from a use of `fromIntegral'
In the second argument of `($)', namely `fromIntegral x'
In the expression: round $ fromIntegral x
In an equation for `toInt': toInt x = round $ fromIntegral x

Any idea on how to fix this?

If you need to find a function that you know the type like Float -> Int then your can search for functions of that type either on Hayoo or Hoogle — Redu
– Redu, Commented Mar 23, 2017 at 13:19

Chad Gilbert · Accepted Answer · 2017-03-23 12:01:42Z

22

Your type annotation specifies that x should be a Float, which means it can't be a parameter to fromIntegral since that function takes an Integral.

You could instead just pass x to round:

toInt :: Float -> Int
toInt x = round x

which in turn can be slimmed down to:

toInt :: Float -> Int
toInt = round

which implies that you may be better off just using round to begin with, unless you have some specialized way of rounding.

answered Mar 23, 2017 at 12:01

Chad Gilbert

36.4k4 gold badges93 silver badges99 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Sajid Anower Over a year ago

That worked, thanks. I feel so silly after someone tells me a solution in Haskell haha

Collectives™ on Stack Overflow

How to convert from Float to Int in Haskell

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related