Converting Strings to Numbers in C++: A Guide

When working with strings and numbers in C++, it's often necessary to convert between the two data types. This can be done using various functions and techniques, each with its own advantages and limitations.

One common approach is to use the `boost::lexical_cast` function, which can be used to convert a string to an integer or floating-point number. For example:

```

int i = boost::lexical_cast(str.c_str());

float f = boost::lexical_cast(str.c_str());

double d = boost::lexical_cast(str.c_str());

```

However, this solution can be problematic when dealing with bad input, as it's difficult to distinguish between valid and invalid inputs.

Another approach is to use the `sscanf` function, which allows you to convert a string to an integer using a format specifier. For example:

```

int i;

sscanf(str.c_str(), '%d', &i);

```

However, this function can also be error-prone if not used carefully, as it's possible to crash the program with huge input data on some versions of libc.

For C++11 compliant compilers, a more elegant solution is available using regular expressions. This involves parsing the input string based on a specified format and extracting the numeric value.

```

#include

int i = std::stoi(str);

float f = std::stof(str);

double d = std::stod(str);

```

In this case, the `std::stoi`, `std::stof`, and `std::stod` functions are used to convert the string to an integer, floating-point number, or double precision floating-point number, respectively.

Finally, it's worth noting that converting strings to numbers can also be done using custom functions. For example, the `toint` function can be used to convert an integer to a string and vice versa.

```

int i = toint(str);

string s = itoa(i);

```

In conclusion, converting strings to numbers in C++ involves interpreting the characters in the string as numerical values. Various functions and techniques are available, each with its own advantages and limitations. By choosing the right approach for your specific use case, you can ensure accurate and efficient conversion between strings and numbers.

C convert string to number