Common Lisp Macro Generating Macros which evaluates arguments

Question

Intention:

I am trying to generate macros using the macro form:

(make-type "int32" 32)

which would produce:

(defmacro make-int32t (name)
  `(quote (:type 'int32t :bit-length 32 :name ,name)))

This generated macro produces something like:

(make-int32t "myvar")

(:TYPE 'INT32T :BIT-LENGTH 32 :NAME "myvar")

Problem:

I am struggling with how to make the macro produce the leading backquote and the commas.

Here is what I have:

(defmacro make-type (type-name bit-length)
  (let*
      ((make-name  (concatenate 'string "make-" type-name))
       (mac-name (intern make-name)))
       `(defmacro ,mac-name (name)
     '(quote (:type ,type-name :bit-length ,bit-length :name "substitued")))))
 ; "substituted" ideally is something like ,name

If I macroexpand I get:

 (macroexpand-1 '(make-type "int32" 32))

(DEFMACRO |make-int32| (NAME)
  ''(:TYPE "int32" :BIT-LENGTH 32 :NAME "substitued"))

If I try to use the macro, I get:

(make-type "int44" 44)
; in: MAKE-TYPE "int44"
;     (SB-INT:NAMED-DS-BIND (:MACRO |make-int44| . DEFMACRO)
;         (NAME)
;         (CDR #:EXPR)
;       (BLOCK |make-int44| ''(:TYPE "int44" :BIT-LENGTH 44 :NAME "substitued")))
; --> SB-INT:BINDING* 
; ==>
;   (LET* ((#:G0 (SB-C::CHECK-DS-LIST (CDR #:EXPR) 1 1 '(# NAME)))
;          (NAME (POP #:G0)))
;     (BLOCK |make-int44| ''(:TYPE "int44" :BIT-LENGTH 44 :NAME "substitued")))
; 
; caught STYLE-WARNING:
;   The variable NAME is defined but never used.
; 
; compilation unit finished
;   caught 1 STYLE-WARNING condition
WARNING: redefining COMMON-LISP-USER::|make-int44| in DEFMACRO

|make-int44|

But if I try to use the macro, it is not defined.

(make-int44 "myvar")
The function COMMON-LISP-USER::MAKE-INT44 is undefined.

Questions

1) How to replace the "substituted" by ,name

2) How to properly do this?

EDIT: I had a typo: MARCO --> Macro, so I changed the question accordingly

This might be helpful: stackoverflow.com/questions/17429521/… — Barmar
– Barmar, Commented Mar 27, 2018 at 21:42
I don't have time to answer now, but google "common lisp double backquote" and "common lisp nested backquote" — Barmar
– Barmar, Commented Mar 27, 2018 at 21:45
A little hint, the macro should probably include something that looks like ','name in place of "substituted" — Barmar
– Barmar, Commented Mar 27, 2018 at 21:48
Alternatively, rather than thinking in terms of backquotes and splicing, how would you construct the form that you need? After after all, ``(defmacro ,mac-name (name) ,@body)` is equivalent (enough) to (list* 'defmacro mac-name (list 'name) body). If you construct the forms that way, you can probably get a working version sooner, and then can try to turn it into a backquote based implementation (if that's still important). — Joshua Taylor
– Joshua Taylor, Commented Mar 27, 2018 at 21:59

Makketronix · Accepted Answer · 2018-03-28 21:23:18Z

2

Thank you all for your input. To close this, I will post an answer to the question based on your comments:

(defmacro make-type (type-name bit-length)
  (let* ((make-name (concatenate 'string "DEFINE-" (string-upcase type-name)))
         (mac-name  (intern make-name)))
      `(defmacro ,mac-name (name)
         `(quote (:type       ,,type-name
                  :bit-length ,,bit-length
                  :name       ,name)))))

It can be used as:

* (define-type "int16" 16)

DEFINE-INT16
* (DEFINE-int16 "myvar")

(:TYPE "int16" :BIT-LENGTH 16 :NAME "myvar")

edited Mar 28, 2018 at 21:23

answered Mar 27, 2018 at 22:11

Makketronix

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2 Comments

Rainer Joswig Over a year ago

style: I would not use MAKE- in MAKE-TYPE. Use something like DEF- or DEFINE- . MAKE- usually would be a function which makes something. What you have is a macro, which defines something.

Makketronix Over a year ago

@Rainer, what would we do without you!

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