Proposal to add 'Elements of Programming' Concepts to std.traits

[Guillaume Chatelet]

That's a *lot* more code but I think we could do something like

struct NoZero {
    private int _value;

    invariant() { assert(_value != 0); }

    this(int x) { _value = x; }

    NoZero opBinary(string op)(const ref NoZero rhs) {
    	return NoZero(mixin("this._value"~op~"rhs._value"));
    }
    NoZero opBinary(string op)(int rhs) {
    	return NoZero(mixin("this._value"~op~"rhs"));
    }
    ref NoZero opUnary(string op)() if(op=="++"||op=="--"){
    	mixin(op~"this._value;");
    	return this;
    }
    ref NoZero opAssign(int rhs) {
    	value = rhs;
    	return this;
    }

    @property int value() const  { return _value; }
    @property void value(int newValue) { _value = newValue; }

    alias this value;
}

void main(){
    NoZero a = 1;
    auto b = a; // copyable
    // --b; would assert
    auto c = b+1;
    auto d = c+a;
}

Note the implementation is incomplete, still need to implement
comparison to bool, operator'!' , unary '+', '-', '~', checks for
overflows. It's a bit of work but I think it can be done.