bolt/rules/tokens.bend source

bolt/rules/tokens.bend on the hub · documented module

# bolt/rules/tokens: helpers the token rules share (put, escape, nat, strings,# twice, arms): significant tokens, literal kinds, Nat literals, case# patterns, and a name's uses under a node.import Baseimport ../../lazy/lazy.bend as Lazyimport ../../syntax/lex.bend as Leximport ../../syntax/tree.bend as Tree# the tokens without space, newlines and commentsdef sig(toks: List<&2, Lex.Tok>) -> List<&2, Lex.Tok>:  match toks:    case Nil{}:      Nil{}    case Con{Lex.Tok{+k, t, l, c}, rest}:      +more = sig(rest)      Bool.pick(List<&2, Lex.Tok>, Lex.significant(k), Lex.Tok{k, t, l, c} <> more, more)# a number, a char or a string literal?def is_lit(k: Lex.TokKind) -> Bool:  match k:    case Lex.TNum{}:      True{}    case Lex.TChar{}:      True{}    case Lex.TStr{}:      True{}    case other:      False{}# digits, then one final `n`: a Nat literal's charsdef nat_ok(cs: List<&2, Char>) -> Bool:  match cs:    case Con{'n', Nil{}}:      True{}    case Con{+c, t}:      Lazy.and_then(Char.is_digit(c), _u => nat_ok(t))    case Nil{}:      False{}# the text without its last char (a Nat literal's digits)def stem(+t: String) -> String:  String.take(t, Nat.sub(String.length(t), 1n))# a Nat literal's value (`12n` is 12); none for anything else or past U32def nat_value(+t: String) -> Maybe<&2, U32>:  Bool.pick(Maybe<&2, U32>, nat_ok(String.to_list(t)), U32.read(stem(t)), None{})# a text's width in charsdef width(t: String) -> U32:  U32.from_nat(String.length(t))# is the first node the keyword?def keyword(n: Tree.Node, +word: String) -> Bool:  match n:    case Tree.NCons{Tree.Leaf{Lex.Tok{Lex.TKey{}, +t, l, c}}, rest}:      String.eq(t, word)    case other:      False{}# a case statement's pattern (its tokens after `case`, the colon and an# inline body included)def pattern(kids: Tree.Node) -> Tree.Node:  match kids:    case Tree.NCons{h, rest}:      rest    case other:      other# does the name appear anywhere under the node?def mentions(n: Tree.Node, +name: String) -> Bool:  match n:    case Tree.Leaf{Lex.Tok{k, +t, l, c}}:      String.eq(t, name)    case Tree.Group{open, kids, close}:      mentions(kids, name)    case Tree.Stmt{kind, kids, body}:      Lazy.or_else(mentions(kids, name), _u => mentions(body, name))    case Tree.NNil{}:      False{}    case Tree.NCons{h, t}:      Lazy.or_else(mentions(h, name), _u => mentions(t, name))