Basic String-Number Conversion
Did you mean "a", "b" or "c" ? To get 1, 2 or 3?
Or you really want to type "abc" to get "123" or say "ac" gets you "13" ?
I agree with @pbejse's questions, and @ВeekeeCZ's pointers, if not with the code in Message 2, which would appear to work only for single-letter input. Multi-letter input could certainly be done, but it would require stepping through the input string one character at a time.
Also, would this concept extend beyond just a few letters at the beginning of the alphabet? To get "KLM" as an output, you would need to type 11 & 12 & 13, presumably in the format "111213", but in that case how is it to know that you don't want the result to be "AAABAC"?
Kent Cooper, AIA 
@Anonymous wrote:
.... I would just want to type "85121215" and get "hello". ... somehow the lisp will have to read the first 2 digits for start. It will read "8" and "5". It will take these two numbers ... if the number is greater than 27 then read as individual numbers only. So "8" and "5" would be stored and then the next two would be evaluated. "12" would be read as "L" ....
That's not going to be unambiguous. "85121215" could be "heababae". What if you want [whether at the start or elsewhere] "ab", not "l"? Either would be "12". For another example, "head" and "hen" would both be "8514" -- how could it know which you intended?
I would suggest you consider using two digits for each, with preceding zeros for the one-digit numbers: 01 for "a", 02 for "b", etc. Then you wouldn't need to have separators/delimiters, and there would never be ambiguity.
But then there's the question of upper-case vs. lower-case letters....
Kent Cooper, AIA
@Anonymous wrote:
..Essentially I would just want to type "85121215" and get "hello". .
Is this some sort of encrypting/decypting code? Did anyone approach you to crack the enigma machine ? 😄
If that's the case, you may also need a key to go with the message. Please tell us more.
Just so you know, I went through the same phase when i was starting to learn how to code
@Sea-Haven wrote:
.... just use the ascii code returned for the letters A=65 a=97 ....
That's valid when going from letters to numbers, since letters are only one character each. But going from numbers to letters still has the problem that not all have the same number of digits. It could work if limited to capital letters and if Users know the appropriate numbers from 65 up and can enter them that way, so that all can be 2-digit numbers. But if you want 1 to represent A, etc., the same issues arise.
Kent Cooper, AIA
Accepted solution
@Anonymous wrote:
I just want my simple letter to number algorithm example lol.
Okay then, now lets play with a simple algorhythm allgorithem algorithm.
You can start by creating a list using direct substitution.
(defun c:input (/ n1 n2 n2l)
(setq n1 '((69 . "05") (72 . "08")(76 . "12")(79 . "15")) )
(if
(and
(setq n2 (strcase (getstring "\nEnter Letters: ")))
(vl-every '(lambda (l)
(assoc l n1))
(setq n2l (vl-string->list n2))
)
)
(print (apply 'strcat
(mapcar '(lambda (c)
(cdr (assoc c n1))
)
n2l
)
)
)
(princ "\nInvalid character input")
)(princ)
)
Command: Input
Enter Letters: Hello
"0805121215"
Or you can use any single character and not necessarily a number to make it easier to decrpyt by replacing n1 list with this
(setq n1 '((69 . "^")(72 . "Z")(76 . "3")(79 . "$")))
Command: Input
Enter Letters: Hello
Z^33$
Which in turn returning it back to "HELLO" is easy using the same code and replacing these two lines
(defun c:output (/ n1 n2 n2l)
(setq n1 '(( 94 . "E")(90 . "H")(51 . "L")(36 . "O")))
...
(setq n2 (strcase (getstring "\nEnter string to decrypt: ")))
...
Command: output
Enter string to decrypt: Z^33$
"HELLO"
You can build the entire substition list to include just about everything.
HTH
@Anonymous wrote:
That is awesome man thank you so much! I will definitely be messing with this a lot and sharing it. Much appreciated, seriously. Everyone will love this.
Anytime LispHunt42, let us know if you need more help with coding a more complex algorithm.
Cheers