Scan.header: def of yaml-for-bend@0.1.1.0
Import: import yaml-for-bend@0.1.1.0/scan.bend as Scan
Lines 1005-1019 of yaml-for-bend@0.1.1.0/scan.bend: https://jend.leeeet.dev/read.txt?path=yaml-for-bend@0.1.1.0/scan.bend&start_line=1005&end_line=1019

import Base

# The indicators after "|" or ">", in either order.
def header(+cur: Cur) -> Head:
  +s = cur.s(cur)
  +c0 = peek(s, 0n)
  +c1 = peek(s, 1n)
  +ch0 = chomp.of(c0)
  +ch1 = chomp.of(c1)
  +d0 = Bool.and(Char.is_digit(c0), Bool.not(Char.is_eq(c0, '0')))
  +d1 = Bool.and(Char.is_digit(c1), Bool.not(Char.is_eq(c1, '0')))
  when(Head, Bool.or(Char.is_eq(c0, '0'), Bool.and(is_some.chomp(ch0), Char.is_eq(c1, '0'))),
    u => HeadBad{"found an indentation indicator equal to 0 while scanning a block scalar"},
    u => when(Head, Bool.and(is_some.chomp(ch0), d1), u => head.end(chomp.or(ch0, Clip{}), digit.value(c1), adv.n(2n, cur)),
      u => when(Head, is_some.chomp(ch0), u => head.end(chomp.or(ch0, Clip{}), 0n, adv(cur)),
        u => when(Head, Bool.and(d0, is_some.chomp(ch1)), u => head.end(chomp.or(ch1, Clip{}), digit.value(c0), adv.n(2n, cur)),
          u => when(Head, d0, u => head.end(Clip{}, digit.value(c0), adv(cur)), u => head.end(Clip{}, 0n, cur))))))

Uses (19):
  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=Char
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Char.is_digit
  https://jend.leeeet.dev/definition.txt?path=Base/base.bend&name=Char.is_eq
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=Chomp
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=Cur
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=Head
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=adv
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=adv.n
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=chomp.of
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=chomp.or
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=cur.s
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=digit.value
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=head.end
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=is_some.chomp
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=peek
  https://jend.leeeet.dev/definition.txt?path=yaml-for-bend@0.1.1.0/scan.bend&name=when