this approach to level 2 is just taking too long to plan, may abandon

1 files changed, 68 insertions, 0 deletions

diff --git a/starts/meaning-vm/level-2-wip-stmtexprs/statementref.cpp b/starts/meaning-vm/level-2-wip-stmtexprs/statementref.cpp
new file mode 100644
index 0000000..2f23dc8
--- /dev/null
+++ b/starts/meaning-vm/level-2-wip-stmtexprs/statementref.cpp
@@ -0,0 +1,68 @@
+#include "statementref.hpp"
+
+#include "concepts.hpp"
+#include "ref.hpp"
+
+using namespace intellect;
+using namespace level2;
+using namespace concepts;
+
+// so, anonymous-assignment is both a statement and an expression.
+// multiple-member-assignment is only an expression: it is an error to evaluate it
+// the submember operator will be both a statement and an expression, but doesn't need to be held as a ref
+// single-member-assignment is mostly a statement: using it as an expression should be an error.
+
+static statementref makebinary(
+	ref lhs, ref kind, ref rhs,
+	std::function<ref(ref)> expraction,
+	std::function<void(ref)> stmtaction
+)
+{
+	a(statement-expresion, kind-expression);
+	ref r = a(kind-expression);
+	r.set(left-operand, lhs);
+	r.set(right-operand, rhs);
+	r.vset(expression-action, expraction);
+	r.vset(statement-action, stmtaction);
+	return r;
+}
+
+statementref::statementref(ref r)
+: r(r.ptr())
+{
+	if (!r.isa(statement-expression)) {
+		throw std::logic_error("that is not a statement expression");
+	}
+}
+
+static void de(ref & r)
+{
+	ref lhs, rhs, expraction, stmtaction;
+
+	try { lhs = r.get(left-operand); } catch(level0::no_such_link_type&) {}
+	try { rhs = r.get(right-operand); } catch(level0::no_such_link_type&) {}
+
+	expraction = r.get(expression-action);
+	stmtaction = r.get(statement-action);
+	dealloc(r);
+	if (lhs != nothing) { dealloc(lhs); }
+	if (rhs != nothing) { dealloc(rhs); }
+	dealloc(expraction);
+	dealloc(stmtaction);
+	r = 0;
+}
+
+statementref::~statementref()
+{
+	if (r == 0) { return; }
+	r.vget<std::function<void(ref)>>(statement-action)(r);
+	de(r);
+}
+
+statementref::operator ref()
+{
+	if (r == 0) { throw std::logic_error("doubly evaluated expression"); }
+	auto ret = r.vget<std::function<void(ref)>>(expression-action)(r);
+	de(r);
+	return ret;
+}