How to compose a string from ascii values

[tonnot]

I have :
int a=47
int b=49
I want to have a string with some line like this (it does not compile)
string C=char(a)+"."+char(c);

Neither I can do:
string C= string((char)a)+"."+string((char)b);

Sincelery I dont know how to write this stupid thing.
Please help

[Bazzy]

string doesn't have a constructor with a single character
Here are two solutions:

string C=  char(a)+string(".")+char(b);
string C = string() + char(a) + "." + char(b);

[tonnot]

Thank you very much