Core.key_once_at: def of bend-schema-lib@0.4.1.0
Import: import bend-schema-lib@0.4.1.0/core.bend as Core
Lines 451-464 of bend-schema-lib@0.4.1.0/core.bend: https://jend.leeeet.dev/read.txt?path=bend-schema-lib@0.4.1.0/core.bend&start_line=451&end_line=464

import Base

# name appears at most once among the keys of the object r. b is whether a key
# read before r was already name; the flag carries forward, and a key that is
# name while the flag is set is the second one -- refused here and nowhere
# else. The value is the first argument because a self-call must read its
# arguments left to right, unchanged until one shrinks, and only the value
# shrinks; the value is matched first because a match cannot be nested inside
# the branch of a match on another parameter. One pass, so a walk costs one
# key per key, the same as the lookup beside it.
def key_once_at(r: Raw, +b: Bool, +name: String) -> Bool:
  match r:
    case RKey{+k, +v, +o}:
      Bool.and(Bool.not(Bool.and(b, String.eq(k, name))), key_once_at(o, Bool.or(b, String.eq(k, name)), name))
    case _:
      True{}

Uses (7):
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.and
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.not
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Bool.or
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=String.eq
  https://jend.leeeet.dev/definition.txt?path=bend-schema-lib@0.4.1.0/core.bend&name=Raw