data Program = Prog [Declaration]
data Declaration = Decl Variable Expression
data Variable = Var String
data Expression = Apply Expression Expression | Abstract Variable
Expression | Variable
Taking the above program abstract syntax, it seems obvious to me that
parsers should output these elements.
For example if we have the following syntax for an abstraction:
'\', {space}, var, {space}, '.', {space}, expression
This clearly relates to the "Abstract Variable Expression" value
constructor.
This might be in combinators:
auto const lam_tok = tokenize(accept(is_char('\\')));
auto const var_tok = tokenize(accept(is_alpha) && many(accept(is_alnum)));
auto const dot_tok = tokenize(accept(is_char('.')));
auto const abs = all(return_abs, discard(lam_tok) && var_tok,
discard(dot_tok) && expr);
So to integrate this with the abstract syntax, we need to assert that:
typename abs::value_type
Is "Abstract Variable Expression" from the AST.
So I would consider the AST itself determines the grammar, and we can
attach a parser to each internal and leaf node of the tree.
Is this good enough?
Keean.
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