Rework Memory Example

This reworks the memory example so that it now: (a) compiles; (b) makes
use of the stdlib (what there is of it) to improve the overall look.
There is an outstanding issue related to the return types of functions.
Specifically, it seems that corset infers the return type when it is not
specified.

pkg/corset/scope.go

@@ -135,9 +135,12 @@ func (p *ModuleScope) Bind(symbol Symbol) bool {
 		binding := p.bindings[bid]
 		// Resolve symbol
 		return symbol.Resolve(binding)
-	} else {
-		// Attempt to lookup in parent
+	} else if p.module != "" {
+		// Attempt to lookup in parent (unless we are the root module, in which
+		// case we have no parent)
 		return p.enclosing.Bind(symbol)
+	} else {
+		return false
 	}
 }
 

pkg/corset/stdlib.lisp

@@ -1 +1,13 @@
 (defpurefun ((vanishes! :@loob) x) x)
+
+(defpurefun ((or! :@loob) x y) (* x y))
+(defpurefun ((eq! :@loob) x y) (- x y))
+
+(defpurefun (prev x) (shift x -1))
+(defpurefun (next x) (shift x 1))
+
+;;
+(defpurefun (if-not-eq lhs rhs then)
+    (if
+     (eq! lhs rhs)
+     then))