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[Axiom-developer] (no subject)

From: daly
Subject: [Axiom-developer] (no subject)
Date: Fri, 27 Mar 2009 11:04:35 -0600

Alex, Heow,

This is a piece of code that extracts source code from a literate file.
The literate file is assumed to be latex. There are two type of syntax
used in Axiom. One is the standard noweb syntax:

  <<thechunkname>>=    -- define the chunkname
  @                    -- end the chunkname
  <<thechunkname>>     -- use the chunkname

The other is a latex syntax:

  \begin{chunk}{thechunkname}  ==> 'define thechunkname
  \end{chunk}                  ==> 'end nil
  \chunk{thechunkname}         ==> 'refer thechunkname

This code will extract a chunk using either syntax:

  (tangle "clweb.pamphlet" "<<*>>")  <== noweb syntax
  (tangle "clweb.pamphlet "*")       <== latex syntax (default)

Axiom is in the process of transitioning from using noweb syntax to
using latex syntax. There are several reasons for this transition.

First, using latex syntax means that the source files (called pamphlets
in Axiom) are now pure latex so there is no need for a "weave" program.
This eliminates one step in the build chain.

Second, using lisp code rather than noweb means that Axiom can read
and understand its own source files without a system call to noweb.

Third, I can extend the system in any way that is useful such as
supporting "inlined" chunks. The noweb code does not seem to allow
me to use chunks in code:

  (defun standardfn <<standardargs>> 
    .... )

but I can easily write a latex macro such as 

  (defun standardfn \inline{standardargs}
    .... )

which latex will properly expand and which my tangle code will
properly expand.

So the upshot is that by using lisp code rather than noweb I can
eliminate a subsystem, eliminate build steps, eliminate system calls
from lisp, distribute standard latex files as sources, and make the
system dynamically extensible with lisp.


;;; This program will extract the source code from a literate file

;;; The *chunkhash* variable will hold the hash table of chunks.

(defvar *chunkhash* nil)

;  (tangle "clweb.pamphlet" "<<*>>")  <== noweb syntax
;  (tangle "clweb.pamphlet "*")       <== latex syntax (default)

;;; tangle takes the name of a file and the chunk to expand
(defun tangle (filename topchunk)
  (setq *chunkhash* (make-hash-table :test #'equal))
  (hashchunks (gcl-read-file filename))
  (expand topchunk))

;;; gcl-read-file
;;; This would be read-sequence in ansi common lisp. Here we read
;;; a line, push it onto a stack and then reverse the stack. The
;;; net effect is a list of strings, one per line of the file.

(defun gcl-read-file (streamname)
 (let (result)
  (with-open-file (stream (open streamname))
   (do (line eof)
      ((eq line 'done) (nreverse result))
    (multiple-value-setq (line eof) (read-line stream nil 'done)) 
    (unless (eq line 'done) (push line result))))))

;;; hashchunks gathers the chunks and puts them in the hash table
;;; if we find the chunk syntax and it is a
;;;   define ==> parse the chunkname and start gathering lines onto a stack
;;;   end    ==> push the completed list of lines into a stack of chunks
;;;              already in the hash table
;;;   otherwise ==> if we are gathering, push the line onto the stack

;;; a hash table entry is a list of lists such as
;;; (("6" "5") ("4" "3") ("2" "1"))
;;; each of the sublists is a set of lines in reverse (stack) order
;;; each sublist is a single chunk of lines. 
;;; there is a new sublist for each reuse of the same chunkname

(defun hashchunks (lines)
 (let (type name chunkname oldchunks chunk gather)
  (dolist (line lines)
   (multiple-value-setq (type name) (ischunk-latex line))
    ((eq type 'define)
      (setq chunkname name)
      (setq gather t))
    ((eq type 'end)
      ;(format t "name= ~a chunk=~s~%" chunkname chunk)
      (setq oldchunks (gethash chunkname *chunkhash*))
      (setf (gethash chunkname *chunkhash*) (push chunk oldchunks))
      (setq gather nil)
      (setq chunk nil))
      (push line chunk))))))

;;; expand will recursively expand chunks in the hash table
;;; latex chunk names are just the chunkname itself e.g. chunkname
;;; noweb chunk names include the delimiters, e.g: <<chunkname>>

;;; a hash table entry is a list of lists such as
;;; (("6" "5") ("4" "3") ("2" "1"))
;;; so to process the chunk we reverse the main list and
;;; for each sublist we reverse the sublist and process the lines

;;; if a chunk name reference is encountered in a line we call expand
;;; recursively to expand the inner chunkname.

(defun expand (chunk)
 (let ((chunklist (gethash chunk *chunkhash*)) type name)
  (dolist (chunk (reverse chunklist))
   (dolist (line (reverse chunk))
    (multiple-value-setq (type name) (ischunk-latex line))
    (if (eq type 'refer) 
      (expand name)
      (format t "~a~%" line))))))

;;; There is a built-in assumption (in the ischunk-* functions)
;;; that the chunks occur on separate lines and that the indentation
;;; of the chunk reference has no meaning.
;;; ischunk-latex  recognizes chunk names in latex convention
;;; There are 3 cases to recognize:
;;;  \begin{chunk}{thechunkname}  ==> 'define thechunkname
;;;  \end{chunk}                  ==> 'end nil
;;;  \chunk{thechunkname}         ==> 'refer thechunkname

(defun ischunk-latex (line)
 (let ((len (length line)) 
       (mark (search "chunk" line))
       (point 0)
       name preline postline)
  (when mark
    ((setq mark (search "\\begin{chunk}{" line)) ; recognize define
      (setq point (position #\} line :start (+ mark 14)))
       ((null point) (values nil nil))
       ((= point 0)  (values nil nil))
         (setq name (subseq line (+ mark 14) point)) 
         ;(print (list 'define name))
         (values 'define name))))
    ((setq mark (search "\end{chunk}" line))     ; recognize end
       ;(print (list 'end nil))
       (values 'end nil))
    ((setq mark (search "\chunk{" line))         ; recognize reference
      (setq point (position #\} line :start (+ mark 6)))
       ((null point) (values nil nil))
       ((= point 0)  (values nil nil))
         (setq name (subseq line (+ mark 6) point)) 
         ;(print (list 'refer name))
         (values 'refer name))))
    (t (values nil nil))))))
;;; ischunk-noweb recognizes chunk names using the noweb convention
;;; There are 3 cases to recognize:
;;;  <<thechunkname>>=  ==> 'define thechunkname
;;;  @                  ==> 'end nil
;;;  <<thechunkname>>   ==> 'refer thechunkname

(defun ischunk-noweb (line)
 (let ((len (length line)) (mark (position #\> line)) (point 0))
   ((and mark                    ; recognize define
         (> len (+ mark 2))
         (char= #\< (schar line 0))
         (char= #\< (schar line 1))
         (char= #\> (schar line (+ mark 1)))
         (char= #\= (schar line (+ mark 2))))
     ;(print (list 'define (subseq line 0 (+ mark 2))))
     (values 'define (subseq line 0 (+ mark 2))))
   ((and mark                    ; recognize reference
         (> len (+ mark 1))
         (char= #\> (schar line (+ mark 1))))
     (setq point (position #\< line))
      (and point
           (< point (- mark 2))
           (char= #\< (schar line (+ point 1))))
        (values 'refer (subseq line point (+ mark 2)))
        (values 'noise nil)))
    ((and (> len 0)                ; end chunk
          (char= #\@ (schar line 0)))
      (values 'end nil))
    (t (values nil nil)))))
;;; show is a trivial debugging utility. it dumps the hashtable
(defun show ()
   #'(lambda (key value) 
      (format t "~a=~% ~a~%~%~%" key value)) *chunkhash*))

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