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Re: get_i [message #54261 is a reply to message #54256]

Wed, 17 June 2020 00:01

mirek
Messages: 14256
Registered: November 2005

Ultimate Member

mirek wrote on Tue, 16 June 2020 21:20

Novo wrote on Tue, 16 June 2020 18:21
Another experiment/suggestion.
I rewrote get_i using variadic template:
template <typename A, typename... T>
constexpr A get_i(int i, const A& p0, const T& ...args)
{
	A list[] = {p0, args...};
	int n = sizeof...(args);
	return list[clamp(i, 0, n)];
}

const char* cr = get_i(1, "zero", "one", "two");
RDUMP(cr);
int ir = get_i(1, 0, 1, 2);
RDUMP(ir);
IMHO, my implementation is much shorter and it will compile faster.
IMHO, macroses __List and __Expand are not needed anymore ...
Yes, you are right about this, I have used old tricks mostly out of habit. I guess I will have to rewrite it all now

Do you see any problems?

template <class T, class V>
constexpr V decode(const T& sel, const V& def)
{
	return def;
}

template <class T>
constexpr const char *decode(const T& sel, const char *def)
{
	return def;
}

template <class T, class K, class V, typename... L>
constexpr V decode(const T& sel, const K& k, const V& v, const L& ...args)
{
	return sel == k ? v : (V)decode(sel, args...);
}

template <class T, class K, typename... L>
constexpr const char *decode(const T& sel, const K& k, const char *v, const L& ...args)
{
	return sel == k ? v : decode(sel, args...);
}


template <class T, class K>
constexpr int findarg(const T& x, const K& k)
{
	return x == k ? 0 : -1;
}

template <class T, class K, typename... L>
constexpr int findarg(const T& sel, const K& k, const L& ...args)
{
	if(sel == k)
		return 0;
	int q = findarg(sel, args...);
	return q >= 0 ? q + 1 : -1;
}

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