S-expressions: Difference between revisions

const parseExpr = tokens =>

until(finished)(readToken)(

Tuple([])(tokens)

);

// finished :: ([Expr], [String]) -> Bool

const finished = ([, tkns]) =>

0 === tkns.length || ")" === tkns[0];

// readToken :: ([Expr], [String]) -> ([Expr], [String])

const readToken = ([exprs, tkns]) =>

0 < tkns.length ? (() => {

const [t, ...ts] = tkns;

// Subforests are introduced by brackets,

return "(" === t ? (

bimap(

xs => exprs.concat([xs])

)(tail)(parseExpr(ts))

// and conclude where brackets close.

) : ")" === t ? (

Tuple(exprs)(ts)

// Other tokens are appended leaves.

) : Tuple(

exprs.concat(atom(t))

)(ts);

})() : Tuple(exprs)(tkns);