CODEWITHSUNDEEP
c++variadic-templatestemplate-meta-programming
Nomad010
Nomad010

Reputation: 283

Matching variables in template metaprogramming c++

I am writing a class in TMP to do some basic string processing. A string is represented as a class variadic template of chars. I want to test if two strings are equal and, if they are, have an associated type present, but I don't know how I would test if two chars are equal at compile-time. My current code looks as follows but doesn't compile for obvious reasons.

template <typename T, char firstChar, char... Chrs>
class NamedType
{
public:
    typedef T Type;

    template <char otherFirst, char... OtherChrs>
    class TypeIfMatch
    {
    };

    template <firstChar, char... OtherChrs>
    class TypeIfMatch
    {
    public:
         typedef NamedType<T, Chrs>::TypeIfMatch<OtherChars>::type type;
    };

    template <>
    class TypeIfMatch
    {
    public:
         typedef Type type;
    };

    static const char name[sizeof...(Chrs) + 1];
};

template const char NamedType::name[sizeof...(Chrs)+1] = {Chrs..., '\0'};

Upvotes: 0

Views: 259

Answers (1)

Columbo
Columbo

Reputation: 60999

If the strings are specializations of a variadic template, just compare the types for equality via std::is_same. The resulting type is an std::integral_constant with bool as the value type -- specifically, either std::true_type or std::false_type.

Upvotes: 3

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