feat: Implement chapter 8

test/manual-suite.spt

@@ -169,7 +169,9 @@ The content and style of chapter 7 are similar to chapter 6. Again, there is a
 `trans/chap7.str` Stratego file defining several of the rules used in the examples
 from the chapter. As before, the examples with a different signature are recast
 into the SPL signature. Specifically, `Z` becomes `False`, `S(x)` becomes
-`Impl(True(), x)`, and `P` becomes `Or`.
+`Impl(True(), x)`, and `P` becomes `Or`. (At least with these choices, all of the
+transformations in the chapter remain valid in the usual semantics for the SPL
+signature, even if a bit unorthodox.)
 **/
 
 test sec7_2_b_ex [[
@@ -200,3 +202,37 @@ test sec7_3_repeat_big_ex [[
   (1 -> (1 -> (1 -> (1 -> 0)))) | 0
 ]] run repeatmaybeAB to Impl(True(), Impl(True(), Impl(True(),
                                                        Impl(True(), False()))))
+
+/** md
+### Chapter 8
+
+This chapter is even more just a collection of interactive examples. In this
+repository we just give some examples of swapping and variable scope using the
+SPL signature, and some free-form examples of term wrapping and projecting.
+There's no attempt to do any of the arithmetic examples because SPL does not have
+an integer type.
+**/
+
+test sec8_3_firstswap_ex [[
+  p | 0
+]] run SwapWithPat to Or(False(), Atom("p"))
+
+test sec8_3_1_swap_ex [[
+  p | 0
+]] run SwapAnon to Or(False(), Atom("p"))
+
+test sec8_3_2_variablescope_fails [[
+  p | 0
+]] run NoSwapTwice fails
+
+test sec8_3_2_localscope_ex [[
+  p | 0
+]] run OkSwapTwice to Or(Atom("p"), False())
+
+test sec8_5_1_wrap_ex [[
+  p
+]] run TermWrap to Or(Atom("p"), Not(Atom("p")))
+
+test sec8_5_2_project_ex [[
+  p | !p
+]] run TermProj to Atom("p")

trans/chap8.str

@@ -0,0 +1,12 @@
+module chap8
+imports signatures/-
+
+rules
+
+   SwapWithPat = ?Or(e1,e2); !Or(e2,e1)
+   SwapAnon = (Or(e1,e2) -> Or(e2,e1))
+   NoSwapTwice = (Or(e1,e2) -> Or(e2,e1)); (Or(e1,e2) -> Or(e2,e1))
+   OkSwapTwice =
+     {e3,e4 : (Or(e3,e4) -> Or(e4,e3))}; {e3,e4 : (Or(e3,e4) -> Or(e4,e3))}
+   TermWrap = !Or(<id>, Not(<id>))
+   TermProj = ?Or(_, Not(<id>))

trans/spoofax_propositional_language.str

@@ -15,6 +15,7 @@ imports
   prop-desugar
   chap6
   chap7
+  chap8
 
 rules // Debugging