def Parse.digits

bend-trace-context@0.2.0.0 · trace_context.bend:353

import Base
import bend-trace-context@0.2.0.0/src/hex.bend as Hex
import bend-trace-context@0.2.0.0/src/digits.bend as Digits

353# Consume exactly n characters as digits, keeping the unconsumed rest of the
354# text. The recursion decreases n, so no length check or unchecked conversion
355# is needed: the result's type already has length n.
356def Parse.digits(n: Nat, text: String, offset: Nat) ->
357  Result<&2, &2, Error, Parsed<n>>:
358  match n:
359    case 0n:
360      Done{Parsed{Digits.DNil{}, text}}
361    case 1n+p:
362      match text:
363        case SNil{}:
364          Fail{UnexpectedEnd{offset}}
365        case SCon{char, tail}:
366          +at = offset
367          do Result<&2, &2, Error, Parsed<1n+p>>:
368            digit : Hex.Digit <- Parse.digit(char, at)
369            parsed : Parsed<p> <- Parse.digits(p, tail, 1n+at)
370            return Parsed.prepend(p, digit, parsed)