Integer + string = ... new string?

[Bv202]

Hi,

I just saw this piece of code:

char alphabet[26];
    for ( int i = 0; i < 26; ++i )
        alphabet[i] = i + 'a';

I don't really understand it. i + 'a', so you make a sum (the integer + the letter 'a')? Why does this work and why do you get the alphabet letters as the result?

Tyvm =)

[R0mai]

Characters are stored as integers in computers, every character has it's own numerical value.
For example 97 == 'a'
See http://www.asciitable.com/ for more.
As in the ASCII table the English alphabet's characters are in a continuous range, we can cheat like in your example. This is equivalent to yours :
alphabet[i] = i + 97;
Also literals in double quote are "strings", and literals in single quote are 'c' characters, the latter represents a single numerical value, while the former is a 0 terminated array of numerical values.

[chrisname]

Which is why typecasting between char and int work.
Numbers are from ASCII 48 (char '0') and letters from 97. The unsigned range is from 0-255.

See how well designed everything is? It all sort of 'fits together'.

[NGen]

This can be used as a form of encryption, however, it is a very... weak encryption.

[chrisname]

Yes but then you could add extra operations, such as sqrt-ing to obfuscate the result.

Anyway, I think you would use hashes for that.

[Alan]

This particular code uses a loop to store the lowercase alphabet into

char alphabet[26];

What you see happening on line 3 constant value of 'a' (based on the ASCII chart) which is 97 being added to the iterator. In C and C++, integers and characters are practically the same thing and can be used together like that...

A good ASCII chart image:
// http://www.cs.utk.edu/~pham/ascii_table.jpg

Here is what it looks like simplified:

alphabet[0] = 0 + 97; // The letter 'a'
alphabet[1] = 1 + 97; // The letter 'b'
alphabet[2] = 2 + 97; // The letter 'c'
alphabet[3] = 3 + 97; // The letter 'd'
// etc... 

The result... an array of 26 bits with all the lowercase letters in it :)

[Bv202]

Ow, I forget this thread.

Thank you very much for the replies, I understand it now :)

[brokenbot]

ahh i c... does this code print the alphabet?

anyways, thanks for posting cool algorithm.