Coding problems

[crackingthecode]

Hey weregoose!! I need your help. I need help to design a prgm that will take text and use a table that can be changed, to encode the text and display the encoded version. it would help if it could decode the encoded text too.
for ex
a b c d e f g h i j k l m n o p q r s t u v w x y z
f g h i j k l m n o p q r s t u v w x y z a b c d e

the top row would represent a letter from the original message.
the bottom row would represent that letter when its been encoded.

visa versa for decoding.
-thanks

[darkstone knight]

im not weregoose but...

"abcdefghijklmnopqrstuvw
sub(ans,26*fpart( (instring(ans,str1) - 5)/26),1

where str1 holds a single letter

of course, you should omit the * sign...

if you want to decode a string of 2 or more chars:


"abcdefghijklmnopqrstuvw -> str2
for(a,1,lengt(str1
ans + sub(str2,26*fpart( (instring(str2,sub(str1,a,1)) - 5)/26),1
end
text(0,0,ans

probaly...

edit: i just released it typed the alpabet wrong...

[Weregoose]

*sigh* How about providing a program that doesn't crash?

crackingthecode, what you are describing is a Caesar cipher with a five-letter offset. That can be carried out with the following...

"ABCDEFGHIJKLMNOPQRSTUVWXYZ
For(X,1,length(Str1
Ans+sub(Ans,1+round(26fPart((inString(Ans,sub(Str1,X,1))+N-1)/26)),1
End
sub(Ans,27,X-1

...with the message in Str1 and N equal to five. You can decode it by storing 26-5 to N to reverse the offset.

Welcome to United-TI! :)

[EDIT]

Ah, I knew that there was an improved way of doing this: Click

[crackingthecode]

i dont mean just the caeser cipher, but mono-alphabetic substitution. one letter subs another letter once. i mean like to change it up...
-thanks for the help though

[crackingthecode]

by the way, weregoose, im sort of new to the terminology. could you please break it down a bit more, so i understand more fully.
thanks- i appreciate it

my current idea is: //str1 is plaintext //str2 is cipher //str3 is ciphertext ps the format of the str2 is abcdefghijklmnopqrstuvwxyz then the cipher:qwertyuiopasdfghjklzxcvbnm
so the str2=abcdefghijklmnopqrstuvwxyzqwertyuiopasdfghjklzxcvbnm
a=q b=w...

while x is less than or equal to length(str1)
If inString(Str2,sub(str1,x,x,))=0
then
sub(str1,x,x,)+str3 store str3
else
instring(str2,sub(str1,x,x)) store L
L+26 store L
sub(str2,L,L)+str3
ans store str3
x+1 store x
end
disp str3

Im getting nowhere with the errors, so HELP
thanks

[Weregoose]

Oh. Okay, well, let's break it down with a simpler program. This will take a message in Str3 and encode it to Str4 by converting each letter in Str1 to the corresponding letter in Str2:

" ABCDEFGHIJKLMNOPQRSTUVWXYZ→Str1
Store the plaintext alphabet.

" NIBQPKYUWCRMOZGVEHFSDLAJTX→Str2
Store the ciphertext alphabet.

Input Str3
Get the message to be encoded.

"?→Str4
Prepare the string that will hold the encoded message.

For(X,1,length(Str3
Set X equal to 1 and start looping with X increasing until it reaches the length of Str3.

sub(Str3,X,1→Str5
Extract the next letter from the message using X.

inString(Str1,Str5→P
Get the position of this letter as it appears in the plaintext alphabet.

sub(Str2,P,1→Str6
Extract the letter at the same position from the ciphertext alphabet.

Str4+Str6→Str4
Add this letter to the encoded string.

End
Mark the end of the loop.

sub(Str4,2,length(Str4)-1→Str4
Remove the ? from the encoded string.

Now, you should realize that are a few ways to improve this – I'll let you present the results of doing so to yourself, however. The basic rule on this one is to use Ans, make a substitution, and repeat.

[crackingthecode]

Thanks alot. That makes so much more sense. im glad i was refered to you.

so to decode, i switch str1 and str2?




By the way, what was wrong with my previous program?

[Weregoose]

I merged your two posts. Please wait something more like an hour before making a double post, thanks. :)

After testing it in the program above, switching Str1 and Str2 in the first and second lines only does indeed turn the encoder into a decoder.

[crackingthecode]

hey weregoose, i made my own program, but i need your help. it won't encode the whole cypher, just the first letter, and sometimes not even that.

"?>str1
"?>str3
"?>str7
if length(str2) does not equal 52
then
"abcdefghijklmnopqrstuvwxyz">str2
goto C
else
MEnu("Choose a option", "encode", E, "decode", D, "Edit cpiher", C, "quit", Q)
lbl C
clrhome
input "Type cipher ", str7
if length(str7) does not equal 26
then
pause "wrong length"
goto C
else
for(x,1,length(str7)
inString(str7,sub(str7,x,1), x +(x does not equal length(str7)))>L
if l does not equal 0
then
pause "duplicate letter
goto C
else
end
sub(str2,1,26)+str7>str2
prgmCODEN
Lbl E
clrhome
input "enter plaintext", str1
1>x
lbl L
while x is less than or equal to length(str1)
instring(str2,sub(str1,x,1))>L
if L<1 or L>26
then
str3+sub(str1,x,1)>str3
x+1>x
goto L
else
L+26>L
str3 + sub(str2, L, 1) > str3
x+1>x
end
sub(str3,2,length(str3)-1>str3
sub(str2,27,26)
clrhome
Output(1,1,ans
output(3,2,str3
stop
lbl D
'This is the decode section that works.
Lbl Q
stop

any help would be appericated.
(i need it asap for school)

[luby]

I see the problem, or at least a pontential problem if length(str2) does not equal 52
then
"abcdefghijklmnopqrstuvwxyz">str2
goto C Memory leak!!
else
Menu("Choose a option", "encode", E, "decode", D, "Edit cpiher", C, "quit", Q)
lbl C
When you jump out of a If Then End set, the Basic Parser Is still looking for an End so it might skip otherwise usefull code. Plus, it causes a memory leak and slows it down. You should rearrange the code.

[Weregoose]

Because this code stops making sense by the time it reaches the first label, I'm going to ask you to rewrite it. Leave out everything except for the bare essentials—no menus, no error catching, and no fancy outputs—and we'll work on adding the small details from there. Okay?

[GloryMXE7]

[ticalcnoah]

Here are even better ones.
→ ≠ ≥ ≤

[crackingthecode]

thanks for the help, but with the help of stranger, i was able to fix the errors just enough for the deadline. ill type the program soon so that you guys can help me shrink it down some more.

[Mapar007]

[Weregoose]

→ = Alt+26, or any 26+256n. Pleasant results are 26, 282, 1818, and 10010.

≥ = Alt+242 or 242+256n, and nice ones are 1010 and 7666; add 1 to get ≤.

≠ = Typing charmap into Run..., or having it handy elsewhere for copy+paste.

[Mapar007]

Oh yeah, the charmap. I only use it for my greek font. (characters /w spirituses and accents)

And my charmap is broken, it doesn't display the keystrokes anymore...