auto-generate key for hash table in common lisp

Question

I would like to generate sequential keys that I can use across a number of hash tables. I will call them 'id1','id2' etc. If ht is my hash table then I would like to make symbols from strings as keys. To add an entry to the hash table I want to so something like:

(setf (gethash (make-symbol "id1") ht) 1)

And then access it again with

(gethash 'id1 ht)

I don't think make-symbol is giving me what I want, and the key 'id1' sn't recognised.

What is the best way to make this key?

Answer 1

Error: symbol should be in a package and needs the correct case

In your case we have:

CL-USER 24 > (symbol-name (make-symbol "id0"))
"id0"

CL-USER 25 > (symbol-package (make-symbol "id0"))
NIL

Make sure that you think about the following:

• intern the symbol in a package
• intern the symbol in the correct package
• make sure the symbol has the correct name with the correct case
• write symbols with the case you intend to use, possibly you need to escape the symbol to preserve the case

Examples:

uppercased symbol and lowercase symbol name -> not eq

CL-USER 26 > (eq 'id0 (intern "id0" "CL-USER"))
NIL

uppercased symbol and uppercase symbol name -> is eq

CL-USER 27 > (eq 'id0 (intern "ID0" "CL-USER"))
T

an escaped&lowercase symbol and a lowercase symbol name -> is eq

CL-USER 28 > (eq '|id0| (intern "id0" "CL-USER"))
T