Question

I am not good with c++ and I cannot find this anywhere, please apologize me if it is a bad question. I have a pointer and I want to know if some names store in this pointer begins with some specific string. As in python something like (maybe it is a bad example):

if 'Pre' in pointer_name:

This is what I have:

 double t = 0;
 for (size_t i =0; i < modules_.size(); ++i){
    if(module_[i].name() == "pre"){  // here is what I want to introduce the condition
        if (modules_[i].status() == 2){
            std::cout << module_[i].name() << "exists" << std::endl;
         }
    }
 } 

Answer 1

The equivalent of Python 'Pre' in string_name is:

string_name.find("Pre") != std::string::npos // if using string

std::strstr(pointer_name, "Pre") // if using char*

The equivalent of Python string_name.startswith('Pre') (“begins with some specific string”) is:

string_name.size() >= 3 && std::equal(string_name.begin(), string_name.begin() + 3, "Pre"); // if using string

string_name.find("Pre") == 0 // less efficient when it misses, but shorter

std::strncmp(pointer_name, "Pre", 3) == 0 // if using char*

In two of those cases, in practice, you might want to avoid using a literal 3 by measuring the string you’re searching for.