Help searching through a string vector

[shoes2908]

Hi, again I am in a rush and can't seem to remember how to search for a certain string in a string vector... heres my code:

cin >> worker_num;
if (cin.fail())
{
cin >> name_mod;
for ( short q = 0; q < list_names.size (); q++)
{
if ( list_names[q] = name_mod) //here is where i am comparing
{
worker = name_mod;
worker_num = (q + 1);
}
}
}
*************** *************** *************** *****
heres the error...
gaurd.cpp:71: error: could not convert
`(+(&list_names )->std::vector<_T p, _Alloc>::operat or[] [with _Tp
= std::string, _Alloc = std::allocator< std::string>](((unsigned
int)q)))->std::basic_str ing<_CharT, _Traits, _Alloc>::operat or=
[with _CharT = char, _Traits = std::char_trait s<char>, _Alloc
= std::allocator< char>](((const std::basic_stri ng<char,
std::char_trait s<char>, std::allocator< char> >&)((const
std::basic_stri ng<char, std::char_trait s<char>, std::allocator< char>
>*)(&name_mod)) ))' to `bool'


Please help

[gpraghuram]

Hi, again I am in a rush and can't seem to remember how to search for a certain string in a string vector... heres my code:

cin >> worker_num;
if (cin.fail())
{
cin >> name_mod;
for ( short q = 0; q < list_names.size (); q++)
{
if ( list_names[q] = name_mod) //here is where i am comparing
{
worker = name_mod;
worker_num = (q + 1);
}
}
}
*************** *************** *************** *****
heres the error...
gaurd.cpp:71: error: could not convert
`(+(&list_names )->std::vector<_T p, _Alloc>::operat or[] [with _Tp
= std::string, _Alloc = std::allocator< std::string>](((unsigned
int)q)))->std::basic_str ing<_CharT, _Traits, _Alloc>::operat or=
[with _CharT = char, _Traits = std::char_trait s<char>, _Alloc
= std::allocator< char>](((const std::basic_stri ng<char,
std::char_trait s<char>, std::allocator< char> >&)((const
std::basic_stri ng<char, std::char_trait s<char>, std::allocator< char>
>*)(&name_mod)) ))' to `bool'


Please help

Hi,
The re is one issue
[code=cpp]
//if ( list_names[q] = name_mod) //here is where i am comparing
//This shuld be like this
if ( list_names[q] == name_mod) //here is where i am comparing

[/code]

I cant comment fully seeing only part of the code.
Provide the code snippet fully that is the calling part and the function so i can check the logic.

Raghuram

[shoes2908]

Hi,
The re is one issue
[code=cpp]
//if ( list_names[q] = name_mod) //here is where i am comparing
//This shuld be like this
if ( list_names[q] == name_mod) //here is where i am comparing

[/code]

I cant comment fully seeing only part of the code.
Provide the code snippet fully that is the calling part and the function so i can check the logic.

Raghuram

wow, i am so dumb...... hahaha thank you

[Studlyami]

I'm sorry, but i thought for strings you can't use the == operator. I thought you had to use the strcmp function. I know with CStrings you can do the compare with the == operator. Have I been missing something all this time?!

[oler1s]

Studlyami, you are familiar with C++ strings, right?

[Studlyami]

I thought so, but apparently I'm an idiot. I some how had it engraved into my brain that you couldn't use the == operator with the standard strings. Now i tested it it works, then i tested using char * == char * and that works too! so i take it strcmp is from the C days and is there to support legacy code? Wow....that's really bad :(

[scruggsy]

I thought so, but apparently I'm an idiot. I some how had it engraved into my brain that you couldn't use the == operator with the standard strings. Now i tested it it works, then i tested using char * == char * and that works too! so i take it strcmp is from the C days and is there to support legacy code? Wow....that's really bad :(

Not quite.
== works for string objects.
When you do char * == char * you're comparing two addresses, not two strings. Generally you want to compare the contents, not the addresses, which is what strcmp is for.

[Studlyami]

I never noticed this before. In the sample program

    char *Testone = "test";
    char *TestTwo = "test2";
    char *TestSame = "test";

    if(Testone == TestTwo)
        cout<<"wrong"<<endl;
    if(Testone == TestSame)
        cout<<"right"<<endl;

    TestTwo = "test";

    if (TestTwo == Testone)
    cout<<"right"<<endl;

How does Testone and TestSame point to the same address? Then TestTwo receives the same address so how does the compiler link these char variables like that? is that the same behavior on other compilers?

[scruggsy]

I never noticed this before. In the sample program
How does Testone and TestSame point to the same address? Then TestTwo receives the same address so how does the compiler link these char variables like that? is that the same behavior on other compilers?

"test" and "test2" are string literals.
Your compiler is using string pooling to save space in the executable by storing each unique string literal only once. That's why testOne and testSame point to the same address. The C++ standard defines string literals as type const char*; however, for the sake of backwards compatibility with C they can be implicitly cast to char*. But to avoid undefined behavior you should always declare a pointer to a string literal as const (or, better, use a std::string).

[Studlyami]

Hey thanks for the information scruggsy that helped clear a few things up.