CODEWITHSUNDEEP
haskell
Nishara Kavindi
Nishara Kavindi

Reputation: 59

Haskell-How to store the return value of a function to a variable?

I wrote a function in Haskell to return a list. I want to get the return value of the function and store in another variable for future use. The code I have written is given below

module Main
 where

import System.IO

    main =do
        let list=doCal


    doCal =do
        hSetBuffering stdin LineBuffering
        putStrLn "Give me a number (or 0 to stop):"
        num <- getLine
        let number = read num
        if number==0
            then 
                return []
            else do 
                rest <-doCal
                return (number:rest)

When I try to run this, I got an error

Cal.hs:7:9: error:
    The last statement in a 'do' block must be an expression
      let list = doCal
  |
7 |         let list=doCal
  |         ^^^^^^^^^^^^^^
Failed, no modules loaded.

How to store the return value of a function to a variable in Haskell?

Upvotes: 0

Views: 2456

Answers (1)

Paul Johnson
Paul Johnson

Reputation: 17806

The same way you already did it with rest in doCal. 

main = do
   list <- doCal

But you also need to have main do something and return a value. So you might write

main = do
   list <- doCal
   print list

This will work because print list returns (), which is a value in Haskell (its just the only value of its type).

Upvotes: 8

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