Re: saving a numeric table to a disk file

[bill@cambridge.apple.com (Bill St. Clair)]

>Hi MCLers,
>
>I am working on a table management system for scientific
>applications. A table consists of a rectangular array of
>objects, typically 20 columns and 20,000 rows usually with floats.
>
>What I am looking for is a way to efficiently write such a table to
>disk and read it back into memory again in order to achieve
>persistency. In Fortran I would simply use an unformatted read/write.
>
>So far I have been using Lisp's print/format to create a .lisp
>ASCII file, which I compile and load later. This approach suffers
>from two inefficiencies: firstly when the ASCII representation is
>generated from the internal Lisp object representation, and secondly
>when I have to compile the file, which takes quite some time om the
>Mac.
>
>Any suggestions? 
>
>Hans-Martin Adorf

One way is illustrated by the file "MCL Help Map.lisp" in the "Library"
folder. It saves a large hash table to a file. You could have a file
named "Save-*array*.lisp" containing the following code:

---------------------------------------------------------

; save-value.lisp

(in-package :ccl)

(setq *value* '#.*value*)

---------------------------------------------------------

Now, you can save and restore values to a fasl file as follows:

---------------------------------------------------------

; save-value-to-file.lisp

(in-package :ccl)

(export '(save-value-to-file read-value-from-file))

(defvar *value*)

(defparameter *save-value-source-file*
  ; Change to another directory if you like
  "ccl:save-value.lisp")

(defun save-value-to-file (value file)
  (let ((*value* value))
    (compile-file *save-value-source-file*
                  :output-file file)))

(defun read-value-from-file (file)
  (let ((*value* nil))
    (load file)
    *value*))