private static void Cond(Evaluator eval, StackFrame frame)
{
switch (frame.state.value)
{
case "-eval-sexp-body-":
frame.temp1 = frame.args;
frame.state = new Atom("-built-in-cond-head-");
break;
case "-built-in-cond-head-":
if (eval.HaveReturn())
{
var condition = eval.TakeReturn();
if (!condition.IsBool)
{
throw new ArgumentException($"Condition must return boolean atom, but found: {condition}!");
}
if ((bool)condition.value)
{
frame.state = new Atom("-built-in-cond-body-");
break;
}
}
if (frame.temp1 != null)
{
frame.temp2 = frame.temp1.atom;
frame.temp1 = frame.temp1.next;
if (!frame.temp2.IsPair)
{
throw new ArgumentException($"Condition element must be list, but found: {frame.temp2}!");
}
eval.CreateFrame("-eval-", frame.temp2.atom, frame.context);
}
else
{
// Ни одно из условий не выполнилось
frame.state = new Atom("-eval-sexp-body-");
eval.Return(Atoms.FALSE);
}
break;
case "-built-in-cond-body-":
if (eval.HaveReturn())
{
eval.CloseFrame();
}
else
{
eval.CreateFrame("-eval-block-", frame.temp2.next, frame.context);
}
break;
}
}
private static void Eval(Evaluator eval, StackFrame frame)
{
if (!eval.HaveReturn())
{
var(expression, ctxAtom) = StructureUtils.Split2(frame.args);
Context ctx = ctxAtom?.value as Context ?? frame.context.value as Context;
eval.CreateFrame("-eval-", expression, ctx);
return;
}
eval.CloseFrame();
}
private static void Apply(Evaluator eval, StackFrame frame)
{
if (eval.HaveReturn())
{
var args = frame.args;
Atom func = args.atom;
Atom rest = StructureUtils.CloneList(args.next.atom);
Function proc = func?.value as Function;
if (proc == null)
{
throw new ArgumentException("First argument must be procedure!");
}
eval.CreateFrame("-eval-", new Atom(func, rest), frame.context);
return;
}
eval.CloseFrame();
}
private static void EvalEach(Evaluator eval, StackFrame frame)
{
if (!eval.HaveReturn())
{
Atom expression = frame.args;
Atom first = frame.args?.atom;
if (first?.value is Context ctx)
{
expression = frame.args?.next;
}
else
{
ctx = frame.context.value as Context;
}
eval.CreateFrame("-eval-block-", expression, ctx);
return;
}
eval.CloseFrame();
}
private static void If(Evaluator eval, StackFrame frame)
{
switch (frame.state.value)
{
case "-eval-sexp-body-":
{
// (cond BlockA BlockB)
(frame.temp1, frame.temp2, frame.temp3) = StructureUtils.Split3(frame.args);
frame.state = new Atom("-built-in-if-cond-");
}
break;
case "-built-in-if-cond-":
{
if (eval.HaveReturn())
{
var condition = eval.TakeReturn();
if (!condition.IsBool)
{
throw new ArgumentException($"Condition must return boolean atom, but found: {condition}!");
}
frame.state = new Atom((bool)condition.value ? "-built-in-if-then-" : "-built-in-if-else-");
}
else
{
eval.CreateFrame("-eval-", frame.temp1, frame.context);
}
}
break;
case "-built-in-if-then-":
{
if (frame.temp2 == null)
{
throw new ArgumentException($"If statement must have at least one block of code!");
}
if (eval.HaveReturn())
{
eval.CloseFrame();
break;
}
eval.CreateFrame("-eval-", frame.temp2, frame.context);
}
break;
case "-built-in-if-else-":
frame.state = new Atom("-eval-sexp-body-");
if (eval.HaveReturn())
{
eval.CloseFrame();
break;
}
if (frame.temp3 == null)
{
eval.Return(null);
}
else
{
eval.CreateFrame("-eval-", frame.temp3, frame.context);
}
break;
}
}
