# -*- mode: org; -*-
* TODO =pp=
  ah, i see: sometimes we do want =write= and =newline=, when a more
  compact representation is desirable.
* CANCELED =debug= based on =er-macro-transformer=
  CLOSED: [2011-02-16 Wed 01:19]
  though syntax-rules is more elegant?

  fail:

  #+BEGIN_SRC scheme :tangle debug-er.scm :shebang #!/usr/bin/env chicken-scheme
    (use chicken extras ports matchable)
    (import-for-syntax matchable)
    
    ;;; (write `(((+ 2 2) ,(+ 2 2)) ((+ 2 3) ,(+ 2 3))))
    (define-syntax debug
      (er-macro-transformer
       (lambda (expression rename compare)
         (match expression
           ((_) '(void))
           ((_ . expressions)
            `(write `,,(map (lambda (expression)
                            `(',expression ,expression))
                          expressions))
            #;`(write `((,',(car expressions) ,(+ 2 2))))
            #;
            `(begin ,@(map (lambda (expression)
                             `(write ',expression ,expression))
                           expressions))
            #;
            `(write
            ,@(map (lambda (expression)
            ``(expression ,,expression))
            expressions)))))))
    
    ,x (debug (+ 2 2) (+ 2 3))
    
  #+END_SRC

  #+BEGIN_SRC scheme :tangle debug-with-output-to-port.scm :shebang #!/usr/bin/env chicken-scheme
    (use chicken ports test)
    (import-for-syntax scheme chicken ports test)
    
    (define-syntax debug
      (syntax-rules ()
        ((_ x ...)
         (with-output-to-port
             (current-error-port)
           (lambda ()
             (write `((x ,x) ...))
             (newline))))))
    
    (let ((output
           (with-output-to-string
             (lambda ()
               (with-error-output-to-port
                (current-output-port)
                (lambda ()
                  (debug '(mein gott) 'etc)))))))
      (display
       (string=?
        "(((quote (mein gott)) (mein gott)) ((quote etc) etc))\n"
        output)))
    
  #+END_SRC
* DONE e.g. syslog
  CLOSED: [2011-02-16 Wed 01:25]
  mechanism for debugging to different streams: stdout, syslog,
  etc. global flag? (yes, a parameter.)

  a wrapper around =(current-error-port)= which syslogs it, for
  instance.

  =(with-output-to-syslog [priority] thunk)= which takes a default
  priority from some parameter?

  #+BEGIN_SRC scheme :tangle with-output-to-syslog.scm :shebang #!/usr/bin/env chicken-scheme
    (use syslog srfi-13 srfi-16 srfi-39 ports debug)
    
    (define default-priority (make-parameter prio/debug))
    
    (define with-output-to-syslog
      (case-lambda
       ((thunk)
        (with-output-to-syslog (default-priority) thunk))
       ((priority thunk)
        (syslog priority (with-output-to-string thunk)))))
    
    (with-output-to-syslog
     (lambda () (display '(mein gott full of stars))))
    
    (define make-syslog-port
      (case-lambda
       (()
        (make-syslog-port (default-priority)))
       ((priority)
        (let ((buffer ""))
          (make-output-port
           (lambda (scribendum)
             (set! buffer (string-append/shared buffer scribendum)))
           noop
           (lambda () (syslog priority buffer)))))))
    
    (define-syntax debug/syslog
      (er-macro-transformer
       (lambda (expression rename compare)
         `(let ((port (make-syslog-port)))
            (with-error-output-to-port
             port
             (lambda ()
               (debug ,@(cdr expression))
               (flush-output port)))))))
    
    (debug/syslog (+ 2 2) (+ 2 3))
    
  #+END_SRC
  #+BEGIN_SRC scheme :tangle test-debug-syslog.scm :shebang #!/usr/bin/env chicken-scheme
    (use debug)
    (debug/syslog (+ 2 2) (+ 2 3))
    
  #+END_SRC

* TODO =untrace=