Convert char to int

[KMagic]

I have googled this basic problem and find this solotion fastest:

  char a = '4';
  int ia = a - '0';

Does the phrase "" a - '0' " have a particular meaning or it's just a syntax in C++? I mean how can it work?

[giblit]

If you look at an ascii table '0' starts at 48 and '9' ends at 57. So in this case '4' is equal to 52 so 52 - 48 = 4.

[YokoTsuno]

Yes it subtracts the ASCII value of 0 from a. ia therefore contains the numerical value of a when it is indeed a number ('0 to '9', single digit)

http://www.asciitable.com

[TwilightSpectre]

The reason it works is because a char is a number. The most common form is that a char stores the ASCII or UTF-8 value for the character, and '4' would be translated into that value (e.g. 52).

In general, you would expect that the numbers would be in order, i.e. 0123456789. So, if you subtract the character with the value for '0' (e.g. 48), you should get the difference in position.

In your example:

char a = '4';      // a  = 52
int ia = a - '0';  // ia = 52 - 48 = 4 

[KMagic]

Got it. Thank you very much.