/
CalculatorModel.elm
77 lines (59 loc) · 2.02 KB
/
CalculatorModel.elm
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module CalculatorModel where
import Char
import Result
import Set
import String
type ButtonType = Regular | Large
buttonSize : ButtonType -> Int
buttonSize size =
case size of
Regular -> 60
Large -> 120
type alias CalculatorState = {
input: String,
operator: String,
number: Float
}
step : String -> CalculatorState -> CalculatorState
step btn state =
if | btn == "C" -> initialState
| btn == "CE" -> { state | input <- "0" }
| state.input == "" && isOper btn -> { state | operator <- btn }
| isOper btn -> {
number = calculate state.number state.operator state.input,
operator = btn,
input = ""
}
| otherwise ->
{ state |
input <-
if | (state.input == "" || state.input == "0")
&& btn == "." -> "0."
| state.input == "" || state.input == "0"
-> btn
| String.length state.input >= 18
-> state.input
| btn == "."
&& String.any (\c -> c == '.') state.input
-> state.input
| otherwise -> state.input ++ btn }
initialState = { number = 0.0, input = "", operator = "" }
isOper : String -> Bool
isOper btn = Set.member btn (Set.fromList ["+","-","*","/","="])
calculate : Float -> String -> String -> Float
calculate number op input =
let number2 =
case String.toFloat input of
Ok n -> n
Err _ -> 0.0
in
if | op == "+" -> number + number2
| op == "-" -> number - number2
| op == "*" -> number * number2
| op == "/" -> number / number2
| otherwise -> number2
showState : CalculatorState -> String
showState {number,input} =
if input == ""
then toString number
else input