diverges-on-two-sides-that-do-not-join.yaml

# SPDX-FileCopyrightText: Copyright (c) 2025 Objectionary.com
# SPDX-License-Identifier: MIT
---
# yamllint disable rule:line-length
# A join on a condition nobody decided: the condition comes down through 𝔻
# and answers a symbol nobody has decided. The join brings both sides to a
# normal form through 𝕄 first, each a call of 'plus' nobody has fired
# (#1954). The calls add other numbers, so no join makes one term of them,
# and the firing writes 'diverged' with the metas of the applications that
# made the two sides, instead of splitting the run (#1996). Its comment tells
# that the two copies of 'plus' first differ at the ρ the protocol hides, and
# that the join names no function to fabricate a formation with (#2043).
symbolic: |
  - λ: L_number_gt
    dataize:
      𝛿1: $.ρ
      𝛿2: $.x
    𝑛: Φ.bool( φ ↦ ⟦ λ ⤍ 𝜎 ⟧ )
  - λ: L_number_plus
    dataize:
      𝛿1: $.ρ
      𝛿2: $.x
    𝑛: Φ.number( φ ↦ ⟦ λ ⤍ 𝜎 ⟧ )
  - λ: L_fork
    dataize:
      𝛿1: $.ρ
    join:
      on: 𝛿1
      left: $.then
      right: $.else
location: 'Q.@'
input: >
  ⟦ bytes(φ) ↦ ⟦⟧,
    bool(φ) ↦ ⟦ if ↦ ⟦ ρ ↦ ∅, then ↦ ∅, else ↦ ∅, λ ⤍ L_fork ⟧ ⟧,
    number(φ) ↦ ⟦
      gt(ρ, x) ↦ ⟦ λ ⤍ L_number_gt ⟧,
      plus(ρ, x) ↦ ⟦ λ ⤍ L_number_plus ⟧ ⟧,
    φ ↦ 5.gt( 0 ).if( 1.plus( 2 ), 3.plus( 4 ) ).φ ⟧
fails: "No entry of --symbolic answers the λ function 'L_fork'"
protocol: |
  𝕄(Φ.φ):
    𝑛·0·1 := 5
    𝑛·0·2 := 𝑛·0·1.gt( x ↦ 0 )
    𝔼(L_number_gt):
      𝔻(Φ.a🌵0):
        𝕄(Φ.a🌵0):
          𝑛·1·1 := 5
          𝑛·1·2 := Φ.bytes( φ ↦ 40-14-00-00-00-00-00-00:Δ )
        𝛿·1·1 := 40-14-00-00-00-00-00-00  # 5.0
      𝛿1·1 := 𝛿·1·1  # 𝔻(ξ.ρ)
      𝔻(Φ.a🌵1):
        𝕄(Φ.a🌵1):
          𝑛·1·3 := 0
          𝑛·1·4 := Φ.bytes( φ ↦ 00-00-00-00-00-00-00-00:Δ )
        𝛿·1·2 := 00-00-00-00-00-00-00-00  # 0.0
      𝛿2·1 := 𝛿·1·2  # 𝔻(ξ.x)
      𝑛·1·5 := Φ.bool( φ ↦ 𝜎1:λ )  # 𝑛
      𝕄(𝑛·1·5):
        𝑛·1·6 := Φ.bool( φ ↦ 𝜎1:λ )
      𝑛·1·7 := 𝑛·1·6  # 𝕄(𝑛·1·5)
    𝑛·0·3 := 𝑛·1·6.if( then ↦ 1.plus( 2 ) )
    𝑛·0·4 := 𝑛·0·3( else ↦ 3.plus( 4 ) )
    𝔼(L_fork):
      𝔻(Φ.a🌵2):
        𝕄(Φ.a🌵2):
          𝑛·2·1 := Φ.bool( φ ↦ 𝜎1:λ )
      𝛿1·2 := 𝔻(𝜎1:λ)  # 𝔻(ξ.ρ)
      𝕄(Φ.a🌵3):
        𝑛·2·2 := 1
        𝑛·2·3 := 𝑛·2·2.plus( x ↦ 2 )
      𝕄(Φ.a🌵4):
        𝑛·2·4 := 3
        𝑛·2·5 := 𝑛·2·4.plus( x ↦ 4 )
      diverged 𝑛·2·3 vs 𝑛·2·5  # they differ at .ρ, and the join names no otherwise