(defun build-symbol (&rest things)
  "Return a symbol in current package with a name assembled from things"
  (intern
   (format nil "~@:(~{~A~}~)" things)))

(defmacro declare-register-name (register-number)
  `(defparameter ,(build-symbol "r" register-number) 0))

(defmacro declare-register-type (register-number)
  `(declaim (type (unsigned-byte 8) ,(build-symbol "r" register-number))))

(defmacro declare-registers()
  `(progn ,@(loop for i from 0 to 31 collect
                  `(progn (defparameter ,(build-symbol "r" i) 0)
                          (declaim (type (unsigned-byte 8) ,(build-symbol "r" i)))))))

(defmacro register+1 (register)
  "Return symbol of register one number higher"
  (let* ((register-string (symbol-name register))
         (register-number (parse-integer (remove #\r register-string))))
    (build-symbol "r" (+ 1 register-number))))

;Declare 32 8bit registers
(declare-registers)

(defparameter carry-flag nil)

(defmacro add (target source)
  "Add without carry"
  `(setf ,target (mod (+ ,target ,source) 255)))

(defmacro addc (target source)
  "Add with carry"
  `(progn (setf ,target (mod (+ ,target ,source) 255))
  (if (< (+ ,target ,source) 255)
      (setf carry-flag t))))