public override LispObject Eval(Cons body, LispEnvironment env)
{
var testForm = Car.Of(body);
var thenForm = Car.Of(Cdr.Of(body));
var elseForm = Car.Of(Cdr.Of(Cdr.Of(body)));
if (env.Eval(testForm).IsTrue)
{
return env.Eval(thenForm);
}
return env.Eval(elseForm);
}
public override LispObject Eval(Cons body, LispEnvironment env)
{
var varForms = body.Car.As<Cons>();
var varSymbols = varForms.Select(x => x.As<Cons>().Car.As<Symbol>()).ToList();
var varInitForms = varForms.Select(x => x.As<Cons>().Cdr.As<Cons>().Car).ToList();
var varStepForms = varForms.Select(x => x.As<Cons>().Cdr.As<Cons>().Cdr.As<Cons>().Car).ToList();
var cadr = body.Cdr.As<Cons>().Car.As<Cons>();
var testForm = cadr.Car;
var resultForms = cadr.Cdr.As<Cons>();
var doBody = body.Cdr.As<Cons>().Cdr.As<Cons>();
var doEnv = new LispEnvironment(env);
SetInitValues(doEnv, varSymbols, varInitForms);
while (doEnv.Eval(testForm).IsNil)
{
new Progn().Eval(doBody, doEnv);
SetStepValues(doEnv, varSymbols, varStepForms);
}
return new Progn().Eval(resultForms, doEnv);
}
protected override void SetStepValues(LispEnvironment doEnv, List<Symbol> varSymbols, List<LispObject> varStepForms)
{
for (int i = 0; i < varSymbols.Count; i++)
{
var val = doEnv.Eval(varStepForms[i]);
doEnv.SetValue(varSymbols[i], val);
}
}
protected override void SetInitValues(LispEnvironment doEnv, List<Symbol> varSymbols, List<LispObject> varInitForms)
{
for (int i = 0; i < varSymbols.Count; i++)
{
var val = doEnv.Eval(varInitForms[i]);
doEnv.AddBinding(varSymbols[i], val);
}
}
public override LispObject Eval(Cons body, LispEnvironment env)
{
var symbol = Car.Of(body).As<Symbol>();
var value = env.Eval(Car.Of(Cdr.Of(body)));
env.SetValue(symbol, value);
return value;
}
public override LispObject Apply(Cons arguments, LispEnvironment env)
{
return env.Eval(arguments.Car);
}