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C#    how to get char - 'A'

Posted on 2010-11-10
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Last Modified: 2012-05-10
I am taking a string "str" full of capitals 'A' thru 'Z' which represents a 26 base number where 'A' = 0, 'B' = 1, and so on.....

part of this operation is a line like so:  

int place_number =  (int)(str[i] - 'A') * (26*(i))

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essentially I just want the numerical difference between a character in the string and 'A', so that 'A' returns 0, 'B' returns 1, and so on....

I am more familiar with C++ that C#, so I'm not understanding the type conversion here.  The compiler keeps saying Error      1      A new expression requires (), [], or {} after type      

I don't understand that.  


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Question by:LindyGeek
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8 Comments
 

Author Comment

by:LindyGeek
ID: 34105507
So, how do I make the compiler happy and still get the result of str[i] - 'A'   ?
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Accepted Solution

by:
Shaun Kline earned 80 total points
ID: 34105636
Maybe this:
int place_number = (((int)str[i]) - ((int)'A')) * (26 * (i));
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Expert Comment

by:elimesika
ID: 34105717
HI

this is because you defined str as a string array, you should define it as a char array
Example:

int i=0;
            char[] str =
            {
                'A',
                'B',
                'C'
            }
            ;
            int place_number = (int) (str[i] - 'A')*(26*(i));

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Author Closing Comment

by:LindyGeek
ID: 34105728
Cumbersome, but that did it!
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Author Comment

by:LindyGeek
ID: 34105737
Sorry elimesika,

looks like I gave the solution credit as you were posting...
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Expert Comment

by:yanoch
ID: 34105789
Hi friend,

Welcome to C# world! ;)

try this:

Convert.ToInt32(str[i] - 'A');
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Expert Comment

by:elimesika
ID: 34105872
LindyGeek

that's ok, I am here to learn , not for the points ;-)
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Expert Comment

by:yanoch
ID: 34106444
Btw, a string is indeed an array of char!

exemple:

[code]
            string myString = "abcdefghijklmnopqrstuvwxyz";
            Console.WriteLine("char at pos {0}:{1}", 10, myString[10]);
[/code]
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