def Utf8.left

bend-trace-context@0.2.0.0 · trace_context.bend:2028

import Base

2028# What is left of a budget after a text, or None once the text exceeds it.
2029# Measuring stops at the first character beyond the budget, and a None budget
2030# stays None.
2031def Utf8.left(text: String, budget: Maybe<&2, Nat>) -> Maybe<&2, Nat>:
2032  match text budget:
2033    case _ None{}:
2034      None{}
2035    case SNil{} Some{left}:
2036      Some{left}
2037    case SCon{char, tail} Some{left}:
2038      Utf8.left(tail, Budget.take(Utf8.width(char), left))