converting number to string in lisp

Question

I tried to find a lisp function to convert between numbers and strings and after a little googling I fond a function with the same name. when I entered (itoa 1) SLIME printed:

Undefined function ITOA called with arguments (1) .

How can I do the conversion?

Solution 1

From number to string:

(write-to-string 5)
"5"

you may transform a string to any numerical notation:

(write-to-string 341 :base 10)
"341"

From string to number:

(parse-integer "5")
5

with some trash

(parse-integer " 5 something not a number" :junk-allowed t)
5

Or use this:

(read-from-string "23 absd")
23

Solution 2

A heavyweight solution is to use FORMAT:

[2]> (format nil "~A" 1)
"1"

There is also WRITE-TO-STRING:

[3]> (write-to-string 10)
"10"

Solution 3

FYI: I believe (itoa #) is only a function in AutoLISP - the LISP variant embedded in AutoCAD drafting software. AutoLISP has far fewer functions than Common Lisp and sometimes identical functions with a different name or functions with the same name that operate differently.

That's probably why it didn't work for you. I use AutoLISP regularly and (itoa #) would do exactly what you want there.

Comments

[Svante]

Do not use read-from-string on externally provided strings, or at least bind *read-eval* to false when you do. Also of note for general number-parsing is the library parse-number.

[lindes]

Thank you for linking to the CLHS. That helps make this answer more useful than it otherwise would be.

[Student]

Seems that (write-to-string) is depracated. Use (number-to-string) instead, see gnu.org/software/emacs/manual/html_node/elisp/….