interpreter tweaks
mhe authored 1 hour ago
afad15cf
AbstractSyntax.md 1.37 KB
Abstract syntax
The operations are listed in the order of precedence as in the languages C and C++ (from low to high), where all the operations in the same line have the same precedence, but this is important for parsing only:
module AbstractSyntax where type Identifier = String
data OpName
=Or
| And
|Eq |Leq|Less|Geq|Greater |Add|Sub |Mul|Div|Mod
| Not
deriving (Show)
— ||
— &&
— ==
— <= < >= >
— + –
— * / % — !
data Expr = Constant Integer
| Var Identifier
| Op OpName [Expr] deriving (Show)
data Program = Identifier := Expr | Block [Program]
| While Expr Program
| If Expr Program
| IfElse Expr Program Program deriving (Show)
Notice that we are using a constructor := in the Program type, written in infix notation. We use monadic parsing to convert from concrete syntax to abstract syntax.
Next: Parser