CODEWITHSUNDEEP
c++stringcomparestring-literals
Anon
Anon

Reputation: 357

How to check if a string is equal to a string literal

I wanted to compare a string to a string literal; something like this:

if (string == "add")

Do I have to declare "add" as a string or is it possible to compare in a similar way?

Upvotes: 29

Views: 147126

Answers (5)

Jan Schultke
Jan Schultke

Reputation: 39385

Option A - use std::string

std::string has an operator overload that allows you to compare it to another string.

std::string string = "add";
if (string == "add") // true

Option B - use std::string_view(C++17)

If one of the operands isn't already a std::string or std::string_view, you can wrap either operand in a std::string_view. This is very cheap, and doesn't require any dynamic memory allocations.

#include <string_view>
// ...

if (std::string_view(string) == "add")
// or
if (string == std::string_view("add"))
// or
using namespace std::string_literals;
if (string == "add"sv)

Option C - use strcmp(compatible with C)

If neither of those options is available, or you ned to write code that works in both C and C++:

#include <string.h>
// ...

const char* string = "add";
if (strcmp(string, "add") == 0) // true

Upvotes: 0

James Eichele
James Eichele

Reputation: 119106

In C++ the std::string class implements the comparison operators, so you can perform the comparison using == just as you would expect:

if (string == "add") { ... }

When used properly, operator overloading is an excellent C++ feature.

Upvotes: 66

masarapmabuhay
masarapmabuhay

Reputation: 514

We use the following set of instructions in the C++ computer language.

Objective: verify if the value inside std::string container is equal to "add":

if (sString.compare(“add”) == 0) { //if equal
    // Execute
}

Upvotes: -1

Algorithmist
Algorithmist

Reputation: 6695

You could use strcmp():

/* strcmp example */
#include <stdio.h>
#include <string.h>

int main ()
{
  char szKey[] = "apple";
  char szInput[80];
  do {
     printf ("Guess my favourite fruit? ");
     gets (szInput);
  } while (strcmp (szKey,szInput) != 0);
  puts ("Correct answer!");
  return 0;
}

Upvotes: -1

Christopher Armstrong
Christopher Armstrong

Reputation: 7953

You need to use strcmp.

if (strcmp(string,"add") == 0){
    print("success!");
}

Upvotes: 7

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