Integer and fractional math in Haskell

Brews cups from a bag of beans, keeping whole-number and fractional math apart.

-- div and mod are whole-number division; (/) refuses to touch an Int.
beansGrams :: Int
beansGrams = 250

cupsBrewed :: Int
cupsBrewed = beansGrams `div` 18

leftoverGrams :: Int
leftoverGrams = beansGrams `mod` 18

-- (*) binds tighter than (+), and fromIntegral lifts an Int to Double.
costPerCup :: Double
costPerCup = (14.5 + 2.0 * 3.25) / fromIntegral cupsBrewed

main :: IO ()
main = do
  putStrLn (show cupsBrewed ++ " cups, " ++ show leftoverGrams ++ " g over")
  print costPerCup

How it works

1. cupsBrewed uses div for whole cups while leftoverGrams uses mod for the remainder.
2. fromIntegral cupsBrewed lifts the count to a Double so (/) type-checks.
3. The parenthesized (14.5 + 2.0 * 3.25) shows multiplication binding tighter than addition.

Keywords and builtins used here

• Double
• IO
• Int
• beansGrams
• costPerCup
• cupsBrewed
• do
• leftoverGrams
• main

The run, in numbers

Lines

18

Characters to type

485

Tokens

68

Three-star pace

80 tpm

At the three-star pace of 80 tokens a minute, this run takes about 51 seconds.

Type this snippet

Step 2 of 3 in Values & types, step 2 of 27 in Language basics.

← Previous Next →