Added programming language fundamentals code. More to come.

OSU Coursework/CS 381 - Programming Language Fundamentals/Homework 3/MiniMiniLogo.hs

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+-- | This module defines the syntax of MiniMiniLogo. It also provides
+--   functions to generate programs that draw some basic shapes.
+--
+--   NOTE: You should not change the definitions in this file!
+--
+module MiniMiniLogo where
+
+--
+-- * Syntax
+--
+
+-- | A program is a sequence of commands.
+type Prog = [Cmd]
+
+-- | The mode of the pen.
+data Mode = Down | Up
+  deriving (Eq,Show)
+
+-- | Abstract syntax of commands.
+data Cmd = Pen Mode
+         | Move Int Int
+  deriving (Eq,Show)
+
+-- | Generate a MiniMiniLogo program that draws a 2x2 box starting from the
+--   specified point. Conceptually, this program looks like the following, but
+--   the additions are carried out in Haskell rather than in MiniMiniLogo.
+--
+--     pen up; move (x,y);
+--     pen down; move (x+2,y); move (x+2,y+2);
+--               move (x,y+2); move (x,y);
+--
+--   >>> box 7 3
+--   [Pen Up,Move 7 3,Pen Down,Move 9 3,Move 9 5,Move 7 5,Move 7 3]
+--
+box :: Int -> Int -> Prog
+box x y = [Pen Up, Move x y, Pen Down,
+           Move (x+2) y, Move (x+2) (y+2), Move x (y+2), Move x y]
+
+-- | Generate an 'X' from (x,y) to (x+w,y+h).
+--
+--   >>> nix 10 10 5 7
+--   [Pen Up,Move 10 10,Pen Down,Move 15 17,Pen Up,Move 10 17,Pen Down,Move 15 10]
+--
+nix :: Int -> Int -> Int -> Int -> Prog
+nix x y w h = [Pen Up, Move x y, Pen Down, Move (x+w) (y+h),
+               Pen Up, Move x (y+h), Pen Down, Move (x+w) y]
+
+-- | Generate a MiniMiniLogo program that draws n steps starting from
+--   point (x,y).
+--
+--   >>> steps 3 2 4
+--   [Pen Up,Move 2 4,Pen Down,Move 2 5,Move 3 5,Move 3 6,Move 4 6,Move 4 7,Move 5 7]
+--
+steps :: Int -> Int -> Int -> Prog
+steps n x y = [Pen Up, Move x y, Pen Down] ++ step n
+  where
+    step 0 = []
+    step n = step (n-1) ++ [Move (x+n-1) (y+n), Move (x+n) (y+n)]
+
+-- | Draw an example picture. The expected output is given on the HW4
+--   description page.
+demo :: Prog
+demo = box 7 3 ++ nix 6 6 4 3 ++ steps 3 2 4