atol(), atoll() and atof() functions in C/C++

09 Jun, 2020
atol(): This function converts a C-type string, passed as an argument to function call, to a long integer. It parses the C-string str interpreting its content as an integral number, which is returned as a value of type long int. The function discards the whitespace characters present at the beginning of the string until a non-whitespace character is found. If the sequence of non-whitespace characters in C-string str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed and zero is returned.Syntax:long int atol ( const char * str )
Parameters: The function accepts one mandatory parameter str which is the representation of an integral number.Return Value: The function returns the converted integral number as a long int. If no valid conversion can be performed, it returns zero.// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array of numbers    char str1[] = "5672345";      // Function calling to convert to a long int    long int num1 = atol(str1);      cout << "Number is " << num1 << "\n";      // char array of numbers of spaces    char str2[] = "10000002  0";      // Function calling to convert to a long int    long int num2 = atol(str2);      cout << "Number is " << num2 << "\n";    return 0;}Output:Number is 5672345
Number is 10000002
atoll(): This function converts a C-type string, passed as an argument to function call, to a long long integer. It parses the C-string str interpreting its content as an integral number, which is returned as a value of type long long int. The function discards the whitespace characters present at the beginning of the string until a non-whitespace character is found.If the sequence of non-whitespace characters in C-string str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed and zero is returned.Syntax:long long int atoll ( const char * str )
Parameters: The function accepts a mandatory parameter str which is the representation of an integral number.Return Value: The function returns the converted integral number as a long long int. If no valid conversion can be performed, it returns zero.// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array of numbers    char big_num1[] = "8239206483232728";      // Function calling to convert to a long int    long long int num1 = atoll(big_num1);      cout << "Number is " << num1 << "\n";      // char array of numbers of spaces    char big_num2[] = "100000 9 1324100";      // Function calling to convert to a long int    long long int num2 = atoll(big_num2);      cout << "Number is " << num2 << "\n";    return 0;}Output:Number is 8239206483232728
Number is 100000
atof() function: This function converts a C-type string, passed as an argument to function call, to double. It parses the C-string str interpreting its content as a floating point number, which is returned as a value of type double. The function discards the whitespace characters present at the beginning of the string until a non-whitespace character is found. If the sequence of non-whitespace characters in C-string str is not a valid floating point number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed and 0.0 is returned.Syntax:double atof ( const char * str )
Parameters: The function accepts a single mandatory parameter str which is the representation of a floating point number.Return Value:The function returns the converted floating point number as a double value. If no valid conversion can be performed, the function returns zero (0.0).Return Value:// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array    char pi[] = "3.1415926535";      // Calling function to convert to a double    double pi_val = atof(pi);      // prints the double value    cout << "Value of pi = " << pi_val << "\n";      // char array    char acc_g[] = "9.8";      // Calling function to convert to a double    double acc_g_val = atof(acc_g);      // prints the double value    cout << "Value of acceleration due to gravity = "         << acc_g_val << "\n";    return 0;}Output:Value of pi = 3.14159
Value of acceleration due to gravity = 9.8

atol(): This function converts a C-type string, passed as an argument to function call, to a long integer. It parses the C-string str interpreting its content as an integral number, which is returned as a value of type long int. The function discards the whitespace characters present at the beginning of the string until a non-whitespace character is found. If the sequence of non-whitespace characters in C-string str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed and zero is returned.Syntax:long int atol ( const char * str )
Parameters: The function accepts one mandatory parameter str which is the representation of an integral number.Return Value: The function returns the converted integral number as a long int. If no valid conversion can be performed, it returns zero.// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array of numbers    char str1[] = "5672345";      // Function calling to convert to a long int    long int num1 = atol(str1);      cout << "Number is " << num1 << "\n";      // char array of numbers of spaces    char str2[] = "10000002  0";      // Function calling to convert to a long int    long int num2 = atol(str2);      cout << "Number is " << num2 << "\n";    return 0;}Output:Number is 5672345
Number is 10000002

Syntax:
long int atol ( const char * str )

Parameters: The function accepts one mandatory parameter str which is the representation of an integral number.
Return Value: The function returns the converted integral number as a long int. If no valid conversion can be performed, it returns zero.
// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array of numbers    char str1[] = "5672345";      // Function calling to convert to a long int    long int num1 = atol(str1);      cout << "Number is " << num1 << "\n";      // char array of numbers of spaces    char str2[] = "10000002  0";      // Function calling to convert to a long int    long int num2 = atol(str2);      cout << "Number is " << num2 << "\n";    return 0;}
Number is 5672345
Number is 10000002

atoll(): This function converts a C-type string, passed as an argument to function call, to a long long integer. It parses the C-string str interpreting its content as an integral number, which is returned as a value of type long long int. The function discards the whitespace characters present at the beginning of the string until a non-whitespace character is found.If the sequence of non-whitespace characters in C-string str is not a valid integral number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed and zero is returned.Syntax:long long int atoll ( const char * str )
Parameters: The function accepts a mandatory parameter str which is the representation of an integral number.Return Value: The function returns the converted integral number as a long long int. If no valid conversion can be performed, it returns zero.// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array of numbers    char big_num1[] = "8239206483232728";      // Function calling to convert to a long int    long long int num1 = atoll(big_num1);      cout << "Number is " << num1 << "\n";      // char array of numbers of spaces    char big_num2[] = "100000 9 1324100";      // Function calling to convert to a long int    long long int num2 = atoll(big_num2);      cout << "Number is " << num2 << "\n";    return 0;}Output:Number is 8239206483232728
Number is 100000

Syntax:
long long int atoll ( const char * str )

Parameters: The function accepts a mandatory parameter str which is the representation of an integral number.
Return Value: The function returns the converted integral number as a long long int. If no valid conversion can be performed, it returns zero.
// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array of numbers    char big_num1[] = "8239206483232728";      // Function calling to convert to a long int    long long int num1 = atoll(big_num1);      cout << "Number is " << num1 << "\n";      // char array of numbers of spaces    char big_num2[] = "100000 9 1324100";      // Function calling to convert to a long int    long long int num2 = atoll(big_num2);      cout << "Number is " << num2 << "\n";    return 0;}
Number is 8239206483232728
Number is 100000

atof() function: This function converts a C-type string, passed as an argument to function call, to double. It parses the C-string str interpreting its content as a floating point number, which is returned as a value of type double. The function discards the whitespace characters present at the beginning of the string until a non-whitespace character is found. If the sequence of non-whitespace characters in C-string str is not a valid floating point number, or if no such sequence exists because either str is empty or it contains only whitespace characters, no conversion is performed and 0.0 is returned.Syntax:double atof ( const char * str )
Parameters: The function accepts a single mandatory parameter str which is the representation of a floating point number.Return Value:The function returns the converted floating point number as a double value. If no valid conversion can be performed, the function returns zero (0.0).Return Value:// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array    char pi[] = "3.1415926535";      // Calling function to convert to a double    double pi_val = atof(pi);      // prints the double value    cout << "Value of pi = " << pi_val << "\n";      // char array    char acc_g[] = "9.8";      // Calling function to convert to a double    double acc_g_val = atof(acc_g);      // prints the double value    cout << "Value of acceleration due to gravity = "         << acc_g_val << "\n";    return 0;}Output:Value of pi = 3.14159
Value of acceleration due to gravity = 9.8

Syntax:
double atof ( const char * str )

Parameters: The function accepts a single mandatory parameter str which is the representation of a floating point number.
Return Value:The function returns the converted floating point number as a double value. If no valid conversion can be performed, the function returns zero (0.0).
Return Value:
// CPP program to illustrate// working of atol() function.#include <bits/stdc++.h>using namespace std;  int main(){    // char array    char pi[] = "3.1415926535";      // Calling function to convert to a double    double pi_val = atof(pi);      // prints the double value    cout << "Value of pi = " << pi_val << "\n";      // char array    char acc_g[] = "9.8";      // Calling function to convert to a double    double acc_g_val = atof(acc_g);      // prints the double value    cout << "Value of acceleration due to gravity = "         << acc_g_val << "\n";    return 0;}
Value of pi = 3.14159
Value of acceleration due to gravity = 9.8

jm1
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