Convert ASCII Value directly to the literal integer value

Question

I'm reading in a text file for a simulated compiler, and I'm trying to tokenize all the literals. When I realize it's a number value, I'm trying to store the number. However, since the entire line I'm reading from is a string, I only get the ASCII value for the number (i.e. 0 becomes 48), when I really need the value 0. Is there any way to obtain the literal value from the string/char I'm looking at?

example:

std::string IR = "set 0, read" int currentIRIndex = 4 // (looking at the 0 char)

IR[currentIRIndex] is 0 if I call it from the << operator, and 48 (the ASCII value of 0) if I assign it to an integer.

Are you looking to convert one character at a time, or parse as many digits as you can find? — Mark Ransom
– Mark Ransom, Commented Apr 28, 2014 at 22:10
Though there are many (better) ways to convert a string to a number, I'm surprised you didn't at least consider cout << IR[currentIRIndex] -48 << "\n"; — DavidO
– DavidO, Commented Apr 28, 2014 at 22:11
I'm only worried about the current number I'm looking at. @DavidO Oh my gosh....what an easy solution. Talk about functional fixedness..... >_< — LeoVannini
– LeoVannini, Commented Apr 28, 2014 at 22:13

Mooing Duck · Accepted Answer · 2014-04-28 22:17:30Z

4

int v = IR[currentIRIndex] - '0';

this will give you the literal value

edited Apr 28, 2014 at 22:17

Mooing Duck

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answered Apr 28, 2014 at 22:11

Boo

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3 Comments

LeoVannini Over a year ago

This didn't seem to work a few minutes ago, but now seems to work. Thanks again.

Mooing Duck Over a year ago

@LeoVannini: Note that this does not always work for the alphabet, but always works for the ten latin numeric digits.

Boo Over a year ago

this work in your use case with 1 char as a number, if you work with number > 9 this will not and you'll have to use solution to transform a string in int like atoi or boost lexical_cast or direclty with the stream

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