[practice] [Common Lisp] CFFI - c-printf example (Common Lisp)

c-printf.lisp

(require :cffi)


(defpackage my-example
  (:use :cl :cffi))

(in-package my-example)
;; example: direct call
(foreign-funcall "printf" :string (format nil "%s: %d~%") ;; need change ~% to \0 in c.(end for string)
                          :string "Hello"
                          :int 10
                          :int) ;; foreign return type


;; define a foreign function, then call it
(defcfun ("printf" c-printf) :int ;; :int is return type
  (format :string) ;; the necessary arg
  &rest) ;; accept other args

(c-printf (format nil "%s: %d~%")
          :string "Hello"  ;; other args need give the types
          :int 10)

;; define a function to auto concate "~%" to format
(defmacro printf (format &rest type-and-args)
  (let ((new-format (concatenate 'string format "~%")))
    `(c-printf (format nil ,new-format) ,@type-and-args)))

(printf "%s:%d~%"
        :string "Hello"
        :int 10)