open System;
let sin = Math.Sin
let cos = Math.Cos
let atan = Math.Atan
let float_of_int x = (float x)
let int_of_float x = (int x)
type logo = | Home
| Forward of int
| Turn of int
| For of int * logo list
let pi = 4.0 * atan 1.0
let dsin t = sin(pi * (float_of_int t) / 180.0)
and dcos t = cos(pi * (float_of_int t) / 180.0)
let rec interpret f (x,y,d) e =
let interpret' (x,y,d) e = match e with
| Home -> (0,0,0)
| Forward(n) -> (x + (int_of_float ((float n) * dsin d)), y + (int_of_float ((float n) * dcos d)), d)
| Turn(n) -> (x, y, d + n)
| For(i, xs) -> if i > 0 then
interpret f (interpret_prog f (x,y,d) xs) (For(i - 1, xs))
else
(x,y,d)
f (x,y,d)
interpret' (x,y,d) e
and interpret_prog f pos xs = match xs with
| x::xs' -> interpret_prog f (interpret f pos x) xs'
| [] -> pos
let current = (0, 0, 0)
let sample = [Home; For(20, [Turn 18; For(36, [Forward 10; Turn 10])])]
let result = interpret_prog (printf "%A") current sample
Useful snippets of F# code, formatted in a way that makes it easy to copy and paste the snippet in the F# Interactive editor.
Sunday, 19 April 2009
LOGO Large Step Interpreter
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1 comment:
Wonderful. Thanks for sharing this, wished there would be more stuff around interpreters and F# on the net.
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