Re: Accessing elements of static array by name
Paul Brettschneider <paul.brettschneider@yahoo.fr> wrote in message...
Hello,
I have a global static array of structs and want to access a given
element using an identifier. I don't want to use the element subscript,
because it will change if I insert elements before the element I
want to access. In assembler I would simply add a label in front
of the element, but this doesn't work in C++.
The following programm snippet might explain what I want to do:
#include <iostream>
class A{ public:
const char *s;
};
static A array[] = { { "a" }, { "b" },
// I wish I could just define a label to a given element like this,
// but this syntax is already used for designated inits (at least in gcc):
// element_c:
{ "c" }, { "d" }, { "e" }, { "f" }, { "g" } };
int
// Access element "c"
std::cout << array[2].s << std::endl;
// Now I wish I could write it this:
// std::cout << element_c.s << std::endl;
// Or maybe:
// std::cout << array::element_c.s << std::endl;
return 0;
}
Is there a way to do this in C++ (maybe some preprocessor tricks)?
Thank you.
PS: This is my first post to usenet, so bear with me.
A std::map might be an option. Depends on how 'locked-in' you are in your
current design.
// - a loose example -
#include <iostream>
#include <string>
#include <map>
class PaulA{ public:
const char *s;
PaulA() : s(0){}
PaulA( char const *ss ) : s(ss){}
};
int main(){ using std::cout; // for NG post
std::map<std::string, PaulA> PaulMap;
PaulMap["a"] = PaulA("a");
PaulMap["b"] = PaulA("because");
PaulMap["c"] = PaulA("c");
std::string key( "d" );
PaulMap[key] = PaulA( key.c_str() );
cout<<" PaulMap[\"a\"] ="<<PaulMap["a"].s<<std::endl;
cout<<" PaulMap[\"b\"] ="<<PaulMap["b"].s<<std::endl;
cout<<" PaulMap[\"c\"] ="<<PaulMap["c"].s<<std::endl;
cout<<" PaulMap[key] ="<<PaulMap[key].s<<std::endl;
std::string keys( "efgh" );
for( size_t i(0); i < keys.size(); ++i ){
std::string tmp( 1, keys.at(i) ); // a bit on the 'ugly' side <G>
PaulMap[ tmp ] = PaulA( tmp.c_str() );
} // for(i)
for( size_t i(0); i < keys.size(); ++i ){
std::string tmp( 1, keys.at(i) );
cout<<" PaulMap["<<tmp<<"] ="
<<PaulMap[tmp].s<<std::endl;
} // for(i)
return 0;
} // main()
/* -output-
PaulMap["a"] =a
PaulMap["b"] =because
PaulMap["c"] =c
PaulMap[key] =d
PaulMap[e] =e
PaulMap[f] =f
PaulMap[g] =g
PaulMap[h] =h
*/
--
Bob R
POVrookie