On Apr 26, 2009, at 9:43 AM, Michele Simionato wrote:
There is no end to my questions.
But you're getting close to understanding the phases :-)
Study the next library and let me know if you have questions.
Aziz,,,
(library (times)
(export expand-time visit-time invoke-time)
(import (rnrs) (srfi :19))
;;; when (times) is expanded
;;; one value per compilation of this library
;;; subsequent initialization still use the same
;;; value computed when (times) is compiled
(define expand-time
(let-syntax ([isodate (lambda (x) (date->string (current-date)
"~5"))])
isodate))
;;; when (times) is visited
;;; one value per visit instance
;;; next time you visit this library, the value is different
(define-syntax visit-time
(let ([isodate (date->string (current-date) "~5")])
(lambda (x) isodate)))
;;; when (times) is invoked
;;; one value per invoke instance
;;; next time you invoke this library, the value is different
(define invoke-time
(let ([isodate (date->string (current-date) "~5")])
(lambda () isodate)))
;;; current-time is when this procedure is called
;;; one value per call to this procedure
(define run-time
(lambda ()
(let ([isodate (date->string (current-date) "~5")])
isodate)))
;;; macro-time is a macro that records when the macro is expanded
;;; one value per occurrence of (macro-time) in the code
(define-syntax macro-time
(lambda (stx)
(let ([isodate (date->string (current-date) "~5")])
isodate)))
)
