Merge branch 'issue_311' into 'master'

Issue 311

Closes #311

See merge request !130

CHANGES.md

@@ -32,6 +32,9 @@ Transformations
   * `induction_arg_ty_lex` is now equivalent to `induction_ty_lex`
   * `induction_arg_pr` now takes an optional argument that indicates what to
     generalize in the induction
+  * `destruct` now destruct `not p` into `p -> false`. `destruct_rec` is
+     allowed to further destruct afterwards.
+    `destruct` can also destruct `true` and `false`.
 
 IDE
   * display of counterexamples in the Task view has been improved

examples/bts/311_destruct.mlw

+use list.List
+use list.Length
+use int.Int
+
+constant x: int
+
+predicate p int
+
+axiom H: not (p 0)
+axiom H1: p 0
+
+goal g: false
+
+axiom H2: false
+
+goal g5: p 5
+
+axiom H3: true
+
+goal g6: p 5

examples/bts/311_destruct/why3session.xml

+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE why3session PUBLIC "-//Why3//proof session v5//EN"
+"http://why3.lri.fr/why3session.dtd">
+<why3session shape_version="6">
+<prover id="0" name="Alt-Ergo" version="2.2.0" timelimit="20" steplimit="0" memlimit="1000"/>
+<file proved="true">
+<path name=".."/>
+<path name="311_destruct.mlw"/>
+<theory name="Top" proved="true">
+ <goal name="g" proved="true">
+ <transf name="destruct" proved="true" arg1="H">
+  <goal name="g.0" proved="true">
+  <transf name="destruct" proved="true" arg1="H">
+   <goal name="g.0.0" expl="destruct premise" proved="true">
+   <proof prover="0"><result status="valid" time="0.00" steps="2"/></proof>
+   </goal>
+   <goal name="g.0.1" proved="true">
+   <transf name="destruct" proved="true" arg1="H">
+   </transf>
+   </goal>
+  </transf>
+  </goal>
+ </transf>
+ <transf name="destruct_rec" proved="true" arg1="H">
+  <goal name="g.0" expl="destruct premise" proved="true">
+  <proof prover="0"><result status="valid" time="0.00" steps="2"/></proof>
+  </goal>
+ </transf>
+ </goal>
+ <goal name="g5" proved="true">
+ <transf name="destruct" proved="true" arg1="H2">
+ </transf>
+ </goal>
+ <goal name="g6" proved="true">
+ <transf name="destruct" proved="true" arg1="H3">
+  <goal name="g6.0" proved="true">
+  <transf name="destruct" proved="true" arg1="H2">
+  </transf>
+  </goal>
+ </transf>
+ </goal>
+</theory>
+</file>
+</why3session>

src/transform/destruct.ml

@@ -248,6 +248,10 @@ let destruct_fmla ~recursive (t: term) =
     in
 
     match t.t_node with
+    | Tfalse ->
+        []
+    | Ttrue ->
+        [[]]
     | Tbinop (Tand, t1, t2) ->
         let l1 = destruct_fmla_exception ~toplevel:false t1 in
         let l2 = destruct_fmla_exception ~toplevel:false t2 in
@@ -321,6 +325,9 @@ let destruct_fmla ~recursive (t: term) =
       else
         (* The hypothesis is trivial because Cs1 <> Cs2 thus useless *)
         [[]]
+    | Tnot t1 ->
+        (* Keep toplevel: this is considered an implication *)
+        destruct_fmla_exception ~toplevel (t_implies t1 t_false)
     | Tif (t1, t2, t3) ->
         let ts2 =
           destruct_fmla_exception ~toplevel:false t2 |>