phino-0.0.152: test-resources/evaluate-packs/joins-a-decorator-with-the-branch-it-decorates-standing-second-when-lenient.yaml

# SPDX-FileCopyrightText: Copyright (c) 2025 Objectionary.com
# SPDX-License-Identifier: MIT
---
# yamllint disable rule:line-length
# The lenient join of #1815 does not care which branch is the decorator: with
# the decorator on the left and the copy it decorates on the right, it answers
# the same decorator. A copy is a decorator of its own symbol too, so the join
# takes the branch with the longer φ chain for the decorator.
symbolic: |
  - λ: L_fork
    morph:
      𝑛1: $.a
      𝑛2: $.b
    join:
      𝑛3: [𝑛1, 𝑛2]
    lenient: true
    𝑛: 𝑛3
location: 'Q.y'
input: '⟦ y ↦ ⟦ a ↦ ⟦ φ ↦ ⟦ φ ↦ ⟦ λ ⤍ 𝜎1 ⟧, neg ↦ ⟦⟧ ⟧ ⟧, b ↦ ⟦ φ ↦ ⟦ λ ⤍ 𝜎2 ⟧, neg ↦ ⟦⟧ ⟧, λ ⤍ L_fork ⟧.φ ⟧'
result: '⟦ φ ↦ 𝜎3:λ, neg ↦ ⟦⟧ ⟧'
protocol: |
  𝕄(Φ.y):
    𝔼(L_fork):
      𝑛1·1 := ⟦ φ ↦ 𝜎1:λ, neg ↦ ⟦⟧ ⟧:φ  # 𝕄(ξ.a)
      𝑛2·1 := ⟦ φ ↦ 𝜎2:λ, neg ↦ ⟦⟧ ⟧  # 𝕄(ξ.b)
      𝔻(𝜎3:λ) ∈ { 𝔻(𝜎1:λ), 𝔻(𝜎2:λ) }
      𝑛3·1 := ⟦ φ ↦ 𝜎3:λ, neg ↦ ⟦⟧ ⟧:φ  # [𝑛1, 𝑛2]
      𝑛·1·1 := 𝑛3·1  # 𝑛
      𝑛·1·2 := 𝑛3·1  # 𝕄(𝑛·1·1)