Simple example of the "atoi" function in c++

Question

Can someone please give a very simple example on how to use the atoi function? I know how it is supposed to work, but most of the examples are in objective C... Which I have trouble reading with since I haven't really learned it yet . Thanks, in advance!

Answer 1

#include <cstdlib>        // wraps stdlib.h in std, fixes any non-Standard content

std::string t1("234");
int i1 = std::atoi(t1.c_str());
int i1b = std::stoi(t1);  // alternative, but throws on failure

const char t2[] = "123";
int i2 = std::atoi(t2);

const char* t3 = "-93.2"; // parsing stops after +/- and digits
int i3 = std::atoi(t3);   // i3 == -93

const char* t4 = "-9E2";  // "E" notation only supported in floats
int i4 = std::atoi(t4);   // i4 == -9

const char* t5 = "-9 2";  // parsing stops after +/- and digits
int i5 = std::atoi(t5);   // i5 == -9

const char* t6 = "ABC";   // can't convert any part of text
int i6 = std::atoi(t6);   // i6 == 0 (whenever conversion fails completely)

const char* t7 = "9823745982374987239457823987";   // too big for int
int i7 = std::atoi(t7);   // i7 is undefined

Because behaviour in this last case is undefined (probably so some implementations can loop adding the next digit to ten times the previous value without spending time checking for signed integer overflow), it's recommended to use std::stoi or std::strtol instead.

See also: cppreference atoi for documentation including examples; stoi