feat(Foundations/Logic): propositional theorems, modal S5 theorems, and MCS consistency foundations

Cslib.lean

@@ -58,6 +58,7 @@ public import Cslib.Foundations.Data.DecidableEqZero
 public import Cslib.Foundations.Data.FinFun.Basic
 public import Cslib.Foundations.Data.FinFun.Update
 public import Cslib.Foundations.Data.HasFresh
+public import Cslib.Foundations.Data.ListHelpers
 public import Cslib.Foundations.Data.Nat.Segment
 public import Cslib.Foundations.Data.OmegaSequence.Defs
 public import Cslib.Foundations.Data.OmegaSequence.Flatten
@@ -69,8 +70,22 @@ public import Cslib.Foundations.Data.Relation
 public import Cslib.Foundations.Data.Set.Saturation
 public import Cslib.Foundations.Data.StackTape
 public import Cslib.Foundations.Lint.Basic
+public import Cslib.Foundations.Logic.Axioms
+public import Cslib.Foundations.Logic.Connectives
 public import Cslib.Foundations.Logic.InferenceSystem
 public import Cslib.Foundations.Logic.LogicalEquivalence
+public import Cslib.Foundations.Logic.Metalogic.Consistency
+public import Cslib.Foundations.Logic.Metalogic.DeductionHelpers
+public import Cslib.Foundations.Logic.ProofSystem
+public import Cslib.Foundations.Logic.Theorems
+public import Cslib.Foundations.Logic.Theorems.BigConj
+public import Cslib.Foundations.Logic.Theorems.Combinators
+public import Cslib.Foundations.Logic.Theorems.Modal.Basic
+public import Cslib.Foundations.Logic.Theorems.Modal.S5
+public import Cslib.Foundations.Logic.Theorems.Propositional.Connectives
+public import Cslib.Foundations.Logic.Theorems.Propositional.Core
+public import Cslib.Foundations.Logic.Theorems.Temporal.FrameConditions
+public import Cslib.Foundations.Logic.Theorems.Temporal.TemporalDerived
 public import Cslib.Foundations.Semantics.FLTS.Basic
 public import Cslib.Foundations.Semantics.FLTS.FLTSToLTS
 public import Cslib.Foundations.Semantics.FLTS.LTSToFLTS
@@ -140,7 +155,13 @@ public import Cslib.Logics.Modal.Basic
 public import Cslib.Logics.Modal.Cube
 public import Cslib.Logics.Modal.Denotation
 public import Cslib.Logics.Propositional.Defs
+public import Cslib.Logics.Propositional.Metalogic.DeductionTheorem
+public import Cslib.Logics.Propositional.Metalogic.MCS
 public import Cslib.Logics.Propositional.NaturalDeduction.Basic
+public import Cslib.Logics.Propositional.NaturalDeduction.FromHilbert
+public import Cslib.Logics.Propositional.ProofSystem.Axioms
+public import Cslib.Logics.Propositional.ProofSystem.Derivation
+public import Cslib.Logics.Propositional.ProofSystem.Instances
 public import Cslib.MachineLearning.PACLearning.Defs
 public import Cslib.MachineLearning.PACLearning.VCDimension
 public import Cslib.MachineLearning.PACLearning.VersionSpace

Cslib/Foundations/Data/ListHelpers.lean

@@ -0,0 +1,71 @@
+/-
+Copyright (c) 2026 Benjamin Brast-McKie. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Benjamin Brast-McKie
+-/
+
+module
+public import Cslib.Init
+
+/-! # Shared List Helper Utilities
+
+Shared `removeAll` definition and supporting lemmas used by all DeductionTheorem
+files (Propositional, Modal, Temporal, Bimodal). Extracted to avoid duplication.
+
+## Main Definitions
+
+- `removeAll`: Remove all occurrences of an element from a list
+- `removeAll_subset_of_subset`: If `A in Gamma'` and `Gamma' subs A :: Delta`,
+  then `removeAll Gamma' A subs Delta`
+- `mem_removeAll_of_mem_of_ne`: Membership in removeAll from membership and inequality
+- `removeAll_subset_removeAll`: removeAll preserves subset relationships
+
+## Aliases
+
+- `removeAll_sub_of_sub`: Alias for `removeAll_subset_of_subset` using `List.Subset`
+- `removeAll_sub_removeAll`: Alias for `removeAll_subset_removeAll` using `List.Subset`
+-/
+
+@[expose] public section
+
+namespace Cslib.Logic.Helpers
+
+/-- Remove all occurrences of `a` from a list. -/
+def removeAll [DecidableEq α] (l : List α) (a : α) : List α :=
+  l.filter (· ≠ a)
+
+theorem removeAll_subset_of_subset [DecidableEq α] {A : α} {Γ' Δ : List α}
+    (h_sub : ∀ x ∈ Γ', x ∈ A :: Δ) (h_mem : A ∈ Γ') :
+    ∀ x ∈ removeAll Γ' A, x ∈ Δ := by
+  intro x hx
+  simp [removeAll, List.mem_filter] at hx
+  obtain ⟨hx_in, hx_ne⟩ := hx
+  have := h_sub x hx_in
+  simp [List.mem_cons] at this
+  rcases this with rfl | h
+  · exact absurd rfl hx_ne
+  · exact h
+
+theorem mem_removeAll_of_mem_of_ne [DecidableEq α] {a x : α} {l : List α}
+    (h_mem : x ∈ l) (h_ne : x ≠ a) : x ∈ removeAll l a := by
+  simp [removeAll, List.mem_filter]
+  exact ⟨h_mem, h_ne⟩
+
+theorem removeAll_subset_removeAll [DecidableEq α] {a : α} {l₁ l₂ : List α}
+    (h : ∀ x ∈ l₁, x ∈ l₂) : ∀ x ∈ removeAll l₁ a, x ∈ removeAll l₂ a := by
+  intro x hx
+  simp [removeAll, List.mem_filter] at hx ⊢
+  exact ⟨h x hx.1, hx.2⟩
+
+/-- Alias using `List.Subset` notation for `removeAll_subset_of_subset`. -/
+theorem removeAll_sub_of_sub [DecidableEq α] {A : α} {Γ' Δ : List α}
+    (h_sub : Γ' ⊆ A :: Δ) (h_mem : A ∈ Γ') :
+    removeAll Γ' A ⊆ Δ :=
+  removeAll_subset_of_subset h_sub h_mem
+
+/-- Alias using `List.Subset` notation for `removeAll_subset_removeAll`. -/
+theorem removeAll_sub_removeAll [DecidableEq α] {a : α} {l₁ l₂ : List α}
+    (h : l₁ ⊆ l₂) : removeAll l₁ a ⊆ removeAll l₂ a :=
+  removeAll_subset_removeAll h
+
+end Cslib.Logic.Helpers