Minor bug in ch8_ip_address.cpp

[nexushoratio]

Issue Overview

Minor bug parsing IP Addresses in ch8_ip_address.cpp

Describe your environment

The following line incorrectly includes square brackets in the character set:

    21      if(str.find_first_not_of("[0123456789]") == std::string::npos)

Steps to Reproduce

1. [1].2.3.4 throws an exception due to stoi("[1]")
2. 1].2.3.4 gives a false positive due to stoi("1]") succeeding with returning 1.

Expected Behavior

[1].2.3.4 and 1].2.3.4 should both fail gracefully.

Current Behavior

$ ./a.out

Enter an IP address in decimal: [1].2.3.4

terminate called after throwing an instance of 'std::invalid_argument'
  what():  stoi
Aborted

$ ./a.out

Enter an IP address in decimal: 1].2.3.4

1].2.3.4 is a valid IP address.

Possible Solution

Remove square brackets, and it works.

$ ./a.out

Enter an IP address in decimal: [1].2.3.4

[1].2.3.4 is not a valid IP address.

$ ./a.out

Enter an IP address in decimal: 1].2.3.4

1].2.3.4 is not a valid IP address.

[kuashio]

Oops, thanks!