public override object Do(KObject args, KEnvironment env, Continuation <KObject> cont)
{
int length = KPair.Length(args);
if (length == -1)
{
throw new RuntimeException("improper list");
}
if (length == 0)
{
throw new RuntimeException("at least one arg expected");
}
else if (length == 1)
{
KObject a = NumbersModule.Check(First(args));
if (a is KFraction)
{
return(new KFraction((a as KFraction).Numerator * -1, (a as KFraction).Denominator));
}
else
{
return(new KDouble((a as KDouble).Value * -1));
}
}
else
{
KObject dif = NumbersModule.Check(First(args));
KObject head = (args as KPair).Cdr;
while (head is KPair)
{
KObject nextNumber = NumbersModule.Check(First(head));
if (dif is KFraction && nextNumber is KFraction)
{
dif = (dif as KFraction).Subtract(nextNumber as KFraction);
}
else
{
KDouble a = NumbersModule.ToInexact(dif);
KDouble b = NumbersModule.ToInexact(nextNumber);
dif = new KDouble(a.Value - b.Value);
}
head = (head as KPair).Cdr;
}
return(dif);
}
}
public override object Do(KObject args, KEnvironment env, Continuation <KObject> cont)
{
int length = KPair.Length(args);
if (length == -1)
{
throw new RuntimeException("improper list");
}
if (length == 0)
{
return(new KFraction(BigInteger.One, BigInteger.One));
}
else
{
// we have a list of at least one elements
// we must fold it to something useful
KObject product = NumbersModule.Check(First(args));
KObject head = (args as KPair).Cdr;
while (head is KPair)
{
KObject nextNumber = NumbersModule.Check(First(head));
if (product is KFraction && nextNumber is KFraction)
{
product = (product as KFraction).Multiply(nextNumber as KFraction);
}
else
{
KDouble a = NumbersModule.ToInexact(product);
KDouble b = NumbersModule.ToInexact(nextNumber);
product = new KDouble(a.Value * b.Value);
}
head = (head as KPair).Cdr;
}
return(product);
}
}