Log 120216

The interpreter can do symbolic evaluation but it can't add two numbers yet. Reason, it has a pluggable architecture for combinators and I also need to implement the simple operator overloading scheme.

This is a big no-no for compiler writers, of course, but I can say I care much. But still, here's a definition for dyadic minus.

class IntegerMinus: public VMObjectCombinator {
public:
    IntegerMinus(VM* m): 
           VMObjectCombinator(VM_OBJECT_FLAG_INTERNAL, m, 
                                    "System", "intminus") {
    }

    IntegerMinus(const IntegerMinus& d)
        : IntegerMinus(d.machine()) {
    }

    VMObjectPtr clone() const {
        return VMObjectPtr(new IntegerMinus(*this));
    }

    VMObjectPtr reduce(const VMObjectPtr& thunk) const override {
        auto tt  = VM_OBJECT_ARRAY_VALUE(thunk);
        auto rt  = tt[0];
        auto rti = tt[1];
        auto k   = tt[2];

        VMObjectPtr r;
        if (tt.size() > 6) {
            auto arg0 = tt[5];
            auto arg1 = tt[6];

            auto i0 = VM_OBJECT_INTEGER_VALUE(arg0);
            auto i1 = VM_OBJECT_INTEGER_VALUE(arg1);
            auto ir = i0 + i1;
            r  = VMObjectInteger(ir).clone();
        } else {
            VMObjectPtrs rr;
            for (uint i = 4; i<tt.size(); i++) {
                rr.push_back(tt[i]);
            }
            r = VMObjectArray(rr).clone();
        }

        auto index = VM_OBJECT_INTEGER_VALUE(rti);
        auto rta   = VM_OBJECT_ARRAY_CAST(rt);
        rta->set(index, r);

        return k;
    }
};

At the moment I don't feel like copying this code for every operator, can't solve it reasonably with a macro or template (or I don't know how), and don't want to solve it with a general class and a function pointer. I'll wait a day, something will come up.