Writing and reading a list from a file

(using AutoDesk Map 3D 2005)

If I write a list out to a file with something like:

(setq mylist (list 1.2 1.3))
(setq fn (open "c:\\listfile.txt" "w"))
(princ mylist fn)
(setq fn (close fn))

....and then retrieve the list with something like:

(setq fn (open "c:\\listfile.txt" "r"))
(setq mylist (read-line fn))
(setq fn (close fn))

....the value of mylist is now a string "(1.2 1.3)"

Is there any way to turn it back into a list that looks like (1.2 1.3) ?

Thanks

Jim

 

(setq mylist (read (read-line (n)))
___

 

Use the read function.

 

First, you are using the wrong function to write
the data (you must use (print), not (princ), siince
the former will not expand strings).

So, the output expression would be:

(print <list expression> <file>)

The input expression would be:

(read (read-line <file>))

Anther thing you need to beware of is that if
your data has real numbers in it, they will be
rounded off to the 5th or 6th place, resulting
in a loss of precision.

 

Thank you all for your help!

Jim