How to create a macro with arbitrary parentheses which are asymetrical (not paired)

Question

I want to define a macro which encapsulates the frequent pattern below. The code is for FLI of lispworks.

(fli:with-foreign-string ;; class name pointer (cn-p ec bc :external-format (external-format)) "BUTTON" (fli:with-foreign-string ;; window name pointer (wn-p ec bc :external-format (external-format)) "Configuartion:server" (let ((grpbx (createwindowex 0 cn-p wn-p (logior ws_visible ws_child bs_groupbox) 0 0 300 420 hwnd 1 (GetModuleHandle-current 0) 0))) (fli:with-foreign-string ;; class name pointer (cn-p ec bc :external-format (external-format)) "EDIT" (fli:with-foreign-string ;; window name pointer (wn-p ec bc :external-format (external-format)) "192.168.200.200" (createwindowex 0 cn-p wn-p (logior ws_visible ws_child ws_border) 10 30 150 30 hwnd 1 (GetModuleHandle-current 0) 0) )))))

The macro I want to create is something like below: THe strs parameter is a list of strings, e.g. ("BUTTON" "Configuartion:server") above, str-syms accumulates the converted strings which will be fed to createwindowex. What confused me was that the strings to be used (cn-p and wn-p) are in the middle of the body, and I had to split the body into 2 parts: part-bdy and &body bdy.

But the problem is part-bdy, which is first part of LET block (before createwindowex), has many parentheses, whose counter parts are only in the send part (&body bdy). Which means the parentheses in part-bdy are not open and cause error when evaluated. Do you have any clever idea to advise me to solve it?

(defmacro with-foreign-string (strs str-syms part-bdy &body bdy) (let ((g (gensym))) (if (null strs) (append part-bdy str-syms bdy) `(fli:with-foreign-string (,g ec bc :external-format (external-format)) ,(car strs) (with-foreign-string ,(cdr strs) ,(cons g str-syms) ,part-bdy ,@bdy)))))

A macro manipulates code, not parentheses. Could you add some detail, e.g. give a small, but complete example? Thanks. — coredump
– coredump, Commented Dec 18, 2016 at 8:18
You seem to be trying to insert your generated symbols in the middle of the body. You should instead let the user provide the symbols with a LET-like construct (with-foreign-strings ((class-name "BUTTON") (window-name "...")) ... (createwindowx 0 class-name window-name ...)) — jkiiski
– jkiiski, Commented Dec 18, 2016 at 8:40

user1461328 · Accepted Answer · 2017-01-10 08:08:44Z

Just want to share that I changed the macro as below:

(defmacro with-foreign-str (strs str-syms bdy) (if (null strs) bdy `(let ((,(car str-syms) (gensym))) (fli:with-foreign-string (,(car str-syms) ec bc :external-format (external-format)) ,(car strs) (with-foreign-str ,(cdr strs) ,(cdr str-syms) ,bdy)))))

then the code code above without using the macro can be rewritten like this:

 (WITH-FOREIGN-STR ("BUTTON" "Configuartion: server") (cn-p wn-p) (let ((grpbx (createwindowex 0 cn-p wn-p (logior ws_visible ws_child bs_groupbox) 0 0 300 420 hwnd 1 (GetModuleHandle-current 0) 0))) (WITH-FOREIGN-STR ("EDIT" "192.168.200.95") (cn-p3 wn-p3) (createwindowex 0 cn-p3 wn-p3 (logior ws_visible ws_child ws_border) 10 30 150 30 hwnd 1 (GetModuleHandle-current 0) 0))))

This is still not so clean but anyway I can manage to simplify the code using macro. There were not so many responses only because I think due to the FLI and win32 API in the code.

Collectives™ on Stack Overflow

How to create a macro with arbitrary parentheses which are asymetrical (not paired)

1 Answer 1

Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Related