CODEWITHSUNDEEP
c++classtemplates
Rena
Rena

Reputation: 646

C++: Template member functions, as in template<typename T> int foo<T>()

I want to define member functions using templates, in a class which is not a template:

class Foo {
    public:
        template <typename T>
        int doThing(T thing, int num);
};

This works. But what I want to do is this:

class Foo {
    public:
        template <typename T>
        int doThing<T>(int num);
};

With this, I get error: expected initializer before ‘<’ token. I don't understand why one works and the other doesn't? Changing typename to class doesn't make any difference.

Is there some way to achieve this?

Edit: More detail as requested: what I want to achieve is to collapse this repetitive code:

class Blob {
    public:
        int read_int8(lua_State *Lua, int offset);
        int read_uint8(lua_State *Lua, int offset);
        int read_int16(lua_State *Lua, int offset);
        int read_uint16(lua_State *Lua, int offset);
        //...
};

int Blob::read_int8(lua_State *Lua, int offset) {
    int8_t *ptr = (int8_t*)this->data;
    lua_pushinteger(Lua, ptr[offset]);
    return 1;
}

int Blob::read_uint8(lua_State *Lua, int offset) {
    uint8_t *ptr = (uint8_t*)this->data;
    lua_pushinteger(Lua, ptr[offset]);
    return 1;
}

int Blob::read_int16(lua_State *Lua, int offset) {
    int16_t *ptr = (int16_t*)this->data;
    lua_pushinteger(Lua, ptr[offset]);
    return 1;
}

int Blob::read_uint16(lua_State *Lua, int offset) {
    uint16_t *ptr = (uint16_t*)this->data;
    lua_pushinteger(Lua, ptr[offset]);
    return 1;
}

Upvotes: 0

Views: 116

Answers (1)

pzed
pzed

Reputation: 837

No need for <T>.

class Foo {
    public:
        template <typename T>
        int doThing(int num);
};

Upvotes: 4

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