what is the better way to determine if a string is number or not?

[kathy]

what is the better way to determine if a string is number or not?

 

[Victor Bazarov]

what is the better way to determine if a string is number or not?

Convert it using 'strtol' or 'strtod' and see if you convert the entire
string. Make use of the "pointer to the error" argument.

V

 

[Gavin Deane]

what is the better way to determine if a string is number or not?

You need to be clear on what formats for a number you are going to
accept.

For a decimal integer like 12345 it's quite easy. Just use
std::string::find_first_not_of, or std::find_if with a predicate based
on isdigit() to see if there are any characters that are not decimal
digits. But what if you want to accept a decimal point 12345.678

or negative numbers
-12345.678

or hexadecimal
123abc

scientific notation
1.234e5

thousands separator
1,234,567 (could be a different character than , for the separator)

You can write code to handle any or all of those, as long as you define
at the outset what is acceptable. There are lots of variations of find
functions in std::string. std::isdigit() could be helpful too.

However, if you are happy to accept any format that iostreams accept,
the simplest way will probably be to attempt to convert the string to a
number and report success or failure.

http://www.parashift.com/c++-faq-lite/misc-technical-issues.html#faq-39.2

Gavin Deane