wrap around alphabet??

[Jeffrey Barrett]

hello, i'm working on a decoder program that lets the user input a key
(integer between 0 and 26) and then subtracts that number from a given
letter to produce a decoded message. for example, 'Y' - 12 = 'M'. My
problem is I would like the program to "wrap around the alphabet" when
it subtracts the key from the original letter. Ex. 'B' - 5 = 'W'.
this must work for lower and uppercase letters. any help would be
greatly appreciated.

[Martin Johansen]

Try something like

#define AlphaWrap(c, n) ((c)-(n)<'A'?(int)'Z'+1+(c)-'A'-(n):(c)-(n))

[Thomas Matthews]

Jeffrey Barrett wrote:

hello, i'm working on a decoder program that lets the user input a key
(integer between 0 and 26) and then subtracts that number from a given
letter to produce a decoded message. for example, 'Y' - 12 = 'M'. My
problem is I would like the program to "wrap around the alphabet" when
it subtracts the key from the original letter. Ex. 'B' - 5 = 'W'.
this must work for lower and uppercase letters. any help would be
greatly appreciated.

Use your favorite search engine for "ROT-13".

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[Jack Klein]

On 13 Jun 2004 15:29:09 -0700, on*********@hotmail.com (Jeffrey
Barrett) wrote in comp.lang.c:

hello, i'm working on a decoder program that lets the user input a key
(integer between 0 and 26) and then subtracts that number from a given
letter to produce a decoded message. for example, 'Y' - 12 = 'M'. My
problem is I would like the program to "wrap around the alphabet" when
it subtracts the key from the original letter. Ex. 'B' - 5 = 'W'.
this must work for lower and uppercase letters. any help would be
greatly appreciated.

char upper_case [] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ";

Think about it, very useful in both directions.

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Jack Klein
Home: http://JK-Technology.Com
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[Jeffrey Barrett]

Martin Johansen <mf**@online.no> wrote in message news:<VL*******************@news2.e.nsc.no>...

Try something like

#define AlphaWrap(c, n) ((c)-(n)<'A'?(int)'Z'+1+(c)-'A'-(n):(c)-(n))

thanks for the help

im very new to c programming, could you explain what the c and n
variables would be?

thanks

[Richard Bos]

Martin Johansen <mf**@online.no> wrote:

Try something like

#define AlphaWrap(c, n) ((c)-(n)<'A'?(int)'Z'+1+(c)-'A'-(n):(c)-(n))

You've tried this using EBCDIC, I suppose? Funny results, what?

Richard

[Allan Bruce]

"Jeffrey Barrett" <on*********@hotmail.com> wrote in message
news:2b**************************@posting.google.c om...

Martin Johansen <mf**@online.no> wrote in message

news:<VL*******************@news2.e.nsc.no>...

Try something like

#define AlphaWrap(c, n) ((c)-(n)<'A'?(int)'Z'+1+(c)-'A'-(n):(c)-(n))

thanks for the help

im very new to c programming, could you explain what the c and n
variables would be?

thanks

It appears to be the char you want to encode, and the number of places to
shift for your encoding. e.g. to encode 'M' 12 spaces, then use
AlphaWrap('M', 12);
Allan