41 lines
1.4 KiB
Haskell
41 lines
1.4 KiB
Haskell
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-- | This module defines the syntax of the Karel language.
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module KarelSyntax where
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-- | A Karel program is a list of macro definitions and a statement to
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-- use as the body of the "main" function.
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type Prog = (Defs,Stmt)
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-- | A macro name.
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type Macro = String
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-- | A list of macro definitions.
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type Defs = [(Macro,Stmt)]
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-- | Cardinal directions.
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data Card = North | South | East | West deriving (Eq,Show)
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-- | Directions relative to the current facing.
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data Dir = Front | Back | Right | Left deriving (Eq,Show)
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-- | Environment queries.
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data Test = Not Test -- boolean negation
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| Facing Card -- am I facing the given cardinal direction?
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| Clear Dir -- can I move in the given relative direction?
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| Beeper -- is there a beeper here?
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| Empty -- is my beeper bag empty?
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deriving (Eq,Show)
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-- | Statements.
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data Stmt = Shutdown -- end the program
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| Move -- move forward
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| PickBeeper -- take a beeper
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| PutBeeper -- leave a beeper
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| Turn Dir -- rotate in place
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| Call Macro -- invoke a macro
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| Iterate Int Stmt -- fixed repetition loop
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| If Test Stmt Stmt -- conditional branch
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| While Test Stmt -- conditional loop
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| Block [Stmt] -- statement block
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deriving (Eq,Show)
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