Add docstrings.

* srt2vtt: Add docstrings to important procedures.

diff --git a/srt2vtt b/srt2vtt
index cbb4c6d5e7474c904f96a0b47c50bedb89aff958..27e0927e23b3b28c7418cbc085e2d4e2e434fad8 100755 (executable)
--- a/srt2vtt
+++ b/srt2vtt
@@ -45,17 +45,23 @@
 (define parse-time
   (let ((regexp (make-regexp "([0-9]+):([0-9]+):([0-9]+),([0-9]+)")))
     (lambda (s)
+      "Parse the SubRip formatted timestamp in the string S into a 4
+element list.  Valid input looks like '00:00:03.417'."
       (let ((match (regexp-exec regexp s)))
         (map (cut match:substring match <>) '(1 2 3 4))))))
 
 (define parse-time-span
   (let ((regexp (make-regexp "([0-9:,]+) --> ([0-9:,]+)")))
     (lambda (s)
+      "Parse the SubRip formatted time span in the string S and return
+two values: the start time and the end time.  Valid input looks like
+'00:00:03.417 --> 00:00:04.936'."
       (let ((match (regexp-exec regexp s)))
         (values (parse-time (match:substring match 1))
                 (parse-time (match:substring match 2)))))))
 
 (define (read-sub-rip port)
+  "Read a SubRip formatted subtitle from PORT."
   (let-values (((id) (string->number (read-line port)))
                ((start end) (parse-time-span (read-line port)))
                ((lines) (let loop ((lines '()))
@@ -66,6 +72,7 @@
     (make-subtitle id start end lines)))
 
 (define (read-sub-rips port)
+  "Read all SubRip formatted subtitles from PORT."
   (reverse
    (let loop ((subs '()))
      (if (eof-object? (peek-char port))
@@ -73,11 +80,13 @@
          (loop (cons (read-sub-rip port) subs))))))
 
 (define (write-time time port)
+  "Write TIME as a WebVTT formatted timestamp to PORT."
   (match time
    ((h m s ms)
     (format port "~a:~a:~a.~a" h m s ms))))
 
 (define (write-web-vtt subtitle port)
+  "Write SUBTITLE as a WebVTT formatted subtitle to PORT."
   (match subtitle
     (($ <subtitle> id start end text)
      (format port "~a~%" id)
@@ -89,10 +98,13 @@
      (newline port))))
 
 (define (write-web-vtts subtitles port)
+  "Write all SUBTITLES as WebVTT formatted subtitles to PORT."
   (format port "WEBVTT~%~%")
   (for-each (cut write-web-vtt <> port) subtitles))
 
 (define (convert input-port output-port)
+  "Read the SubRip formatted subtitles from INPUT-PORT and write the
+WebVTT equivalents to OUTPUT-PORT."
   (write-web-vtts (read-sub-rips input-port) output-port))
 
 (define (show-help-and-exit)
@@ -140,6 +152,12 @@ Convert SubRip formatted subtitles to WebVTT format.~%")
                   (alist-cons 'output arg args)))))
 
 (define (make-call-with-port-or-file file-proc)
+  "Create a new procedure that accepts two arguments: a port or file,
+and a procedure.  When the returned procedure is called with a port as
+the first argument, the second argument is simply applied with that
+port.  If the first argument is a string, the second argument is
+applied with the port corresponding to the file name contained in the
+string as opened by FILE-PROC."
   (lambda (port-or-file proc)
     (if (port? port-or-file)
         (proc port-or-file)
@@ -152,6 +170,9 @@ Convert SubRip formatted subtitles to WebVTT format.~%")
   (make-call-with-port-or-file call-with-output-file))
 
 (define (parse-opts args)
+  "Parse the list of ARGS and return a list of option/value pairs.
+When an option isn't specified in ARGS, it defaults to the value in
+'%default-args'."
   (args-fold args
              %options
              (lambda (opt name arg args)
@@ -161,6 +182,7 @@ Convert SubRip formatted subtitles to WebVTT format.~%")
              %default-args))
 
 (define (main args)
+  "srt2vtt entry point."
   (let ((opts (parse-opts args)))
     (call-with-port-or-input-file (assoc-ref opts 'input)
       (lambda (input-port)