Some crude snippets from a Pascal-C (I never could decide) self-educational compiler/toy I wrote a while ago (in Haskell): -- a parser function that matche

Some crude snippets from a Pascal-C (I never could decide) self-educational compiler/toy I wrote a while ago (in Haskell): -- a parser function that matches on { ... } returning ... -- can be combined with other parsers braces = (symbol "{") `between` (symbol "}") ... -- a statement is a controlFlow or a declaration or an assignment statement = controlFlow <|> declaration <|> assignment -- a block is either 1 or more statements surrounded by { ... } -- or a single statement. block = (braces $ many statement) <|> statement ... -- An expression is a number, or a variable, or a binary operation -- derive functionality to print and test equality of these values. data Expr = Num Int | Var Variable | DualOp Op Expr Expr ... deriving (Show, Eq) ... foldConstants (DualOp Add (Num a) (Num b)) = Num (a + b) ... Parser combinators (parser functions that take other parser functions and return more complex combined parser functions) with enough syntactic sugar can express BNF-like grammars directly as code. And ML-style list and pattern matching operations are very expressive for operating on the intermediate representation.