feat: implement Chapter 7

trans/chap7.str

@@ -0,0 +1,15 @@
+module chap7
+imports libstrategolib signatures/-
+
+rules
+
+  A : Or(False(), x) -> x
+  B : Or(Impl(True(),x), y) -> Or(x, Impl(True(), y))
+
+strategies
+
+  BthenA = B; A
+  Btwice = B; B
+  maybeB-id-thenB = (B <+ id); B
+  maybeBtwice-idthenB = Btwice <+ (id; B)
+  repeatmaybeAB = repeat(A <+ B)

trans/spoofax_propositional_language.str

@@ -14,6 +14,7 @@ imports
   prop-eval2
   prop-desugar
   chap6
+  chap7
 
 rules // Debugging