Re: Expanding list into string within a command

[Jean Louis <bugs@gnu.support>]

* arthur miller <arthur.miller@live.com> [2020-12-06 22:57]:
> "So I was thinking to use macro that will expand the list within a command."
> 
> Try smth like this:
> (my-macro (command &rest list)
>   (dolist (item `,@list)
>     (dosnth with your list item here)))
> 
> Kind of, if that is what yiu want, I am not sure really what you are after here, but I use that as an idiom quite a lot.

Thank you.

I had to use `apply' when passing `args' that I get from &rest

Now I have made the function better that takes input as string,
processes outside command and returns output as string:

(defun rcd-command-output-from-input (program input &rest args)
  "Returns output from PROGRAM INPUT with optional ARGS"
  (let* ((output (with-temp-buffer
		  (insert input)
		  (apply #'call-process-region nil nil program t t nil args)
		  (buffer-string))))
    output))

Which is also handy for some text processing like:

(defun markdown (text)
  (rcd-command-output-from-input "markdown" text))

(markdown "## Hello")
"<h2>Hello</h2>
"

Then I have improved the generic function to accept any `cs2cs'
format which is tool for conversion of geographic coordinates:

(defun syogm-cs2cs (coord-string &rest cs2cs-format)
  (let* ((command "cs2cs")
	 (cs2cs (apply #'rcd-command-output-from-input command coord-string cs2cs-format))
	 (output (string-trim cs2cs))
	 (output (split-string output "\t"))
	 (lat (pop output))
	 (output (split-string (car output) " "))
	 (lon (pop output)))
    (format "%s %s" lat lon)))

And now this works:

(syogm-cs2cs "5d15'57.76\"S 35d8'22.65\"E" "-f" "%.6f" "+proj=latlong" "+datum=WGS84" "+to" "+proj=latlong" "+datum=WGS84")

Then I can make new functions like:

(defun syogm-dms2dd (coord-string)
  "Convert DMS degree, minutes and seconds notation to DD decimal notation"
  (syogm-cs2cs coord-string "-f" "%.6f" "+proj=latlong" "+datum=WGS84" "+to" "+proj=latlong" "+datum=WGS84"))

Then it converts to acceptable result from degree, minutes,
seconds to decimal notation:

(syogm-dms2dd "5d15'57.76\"S 35d8'22.65\"E")
"-5.266044 35.139625"

as then I can convert Ugandan UTM zone 36N with geodetic datum
ARC1960 easier to WGS84 system used on mobile devices and maps of
today:

(defun syogm-convert-arc-1964-utm-36N-to-wgs-84 (earthing-northing)
  "Converts UTM Zone 36N Arc 1960 geodetic datum to WGS84"
  (syogm-cs2cs earthing-northing "-f" "%.5f" "EPSG:21096" "EPSG:4326"))

(syogm-convert-arc-1964-utm-36N-to-wgs-84 "137878 -125964")
"-1.14052 29.74755"

Which is final result I wanted to get, as only so I can request
download of maps from online providers.

Although I have been doing that conversion myself with Common Lisp already, but now I just wish to use external tool.

(defun ll-number (d)
  (let ((l (- (length d) 1)))
    (if (integerp (read-from-string (first-char d)))
	(substring d 0 l)
	d)))

(defun ll-parts (coord)
  (let ((ll-list (split-by-one-space coord)))
    (delete-if #'string-emptyp ll-list)
    (setf ll-list (map 'list #'(lambda (s) (string-trim '(#\Space) s)) ll-list))
    (setf ll-list (map 'list #'(lambda (s) (ll-number s)) ll-list))
    ll-list))

(defun dms2dd-degrees (d)
  (truncate d))

(defun dms2dd-minutes (m)
  (float (/ m 60)))

(defun dms2dd-seconds (s)
  (float (/ s 3600)))

(defun dms2dd (coord)
  (let* ((ll-list (ll-parts coord))
	 (degrees (car ll-list))
	 (minutes (cadr ll-list))
	 (seconds (caddr ll-list))
	 (cardinal (cadddr ll-list))
	 (dd (+ (dms2dd-degrees (read-from-string degrees))
		(dms2dd-minutes (read-from-string minutes))
		(dms2dd-seconds (read-from-string seconds)))))
	 (if (or (string= "S" cardinal) (string= "W" cardinal))
	     (- dd)
	     dd)))