Name the subterm-handling instructions something not completely stupid
The `unify-*` instructions in the original WAM are used both in both program
mode and query mode. In program mode, they are used to unify subterms of
arguments with things. In query mode, they are used to write the subterms of
the arguments into the head.
You may have noticed the common word in both of these descriptions is "subterm"
and not "unify". Let's use that word to name the instructions so it's less
confusing.
| author |
Steve Losh <steve@stevelosh.com> |
| date |
Sun, 10 Jul 2016 14:28:48 +0000 |
| parents |
792dfa2f9120 |
| children |
23d4dc2900a1 |
(in-package #:bones.wam)
(deftype cell ()
`(unsigned-byte ,+cell-width+))
(deftype cell-tag ()
`(unsigned-byte ,+cell-tag-width+))
(deftype cell-value ()
`(unsigned-byte ,+cell-value-width+))
(deftype store-index ()
`(integer 0 ,(1- +store-limit+)))
(deftype heap-index ()
`(integer ,+heap-start+ ,(1- +store-limit+)))
(deftype stack-index ()
`(integer ,+stack-start+ ,(1- +stack-end+)))
(deftype trail-index ()
`(integer 0 ,(1- +trail-limit+)))
(deftype register-index ()
`(integer 0 ,(1- +register-count+)))
(deftype functor-index ()
`(integer 0 ,(1- +functor-limit+)))
(deftype arity ()
`(integer 0 ,+maximum-arity+))
(deftype functor ()
'(cons symbol arity))
(deftype code-word ()
`(unsigned-byte ,+code-word-size+))
(deftype code-index ()
;; either an address or the sentinel
`(integer 0 ,(1- +code-limit+)))
(deftype opcode ()
`(integer 0 ,(1- +number-of-opcodes+)))
(deftype stack-frame-size ()
`(integer 4 ,+stack-frame-size-limit+))
(deftype stack-choice-size ()
;; TODO: is this actually right? check on frame size limit vs choice point
;; size limit...
`(integer 7 ,+stack-frame-size-limit+))
(deftype stack-frame-argcount ()
'arity)
(deftype continuation-pointer ()
'code-index)
(deftype environment-pointer ()
'stack-index)
(deftype backtrack-pointer ()
'stack-index)
(deftype stack-frame-word ()
'(or
environment-pointer ; CE
continuation-pointer ; CP
stack-frame-argcount ; N
cell)) ; Yn
(deftype stack-choice-word ()
'(or
environment-pointer ; CE
backtrack-pointer ; B
continuation-pointer ; CP, BP
stack-frame-argcount ; N
trail-index ; TR
heap-index ; H
cell)) ; An
(deftype stack-word ()
'(or stack-frame-word stack-choice-word))
;;;; Sanity Checks
;;; The values on the WAM stack are a bit of a messy situation. The WAM store
;;; is defined as an array of cells, but certain things on the stack aren't
;;; actually cells (e.g. the stored continuation pointer).
;;;
;;; This shouldn't be a problem (aside from being ugly) as long as our `cell`
;;; type is big enough to hold the values of these non-cell things. So let's
;;; just make sure that's the case...
(defun sanity-check-stack-type (type)
(assert (subtypep type 'cell) ()
"Type ~A is too large to fit into a cell!"
type)
(values))
(sanity-check-stack-type 'stack-frame-argcount)
(sanity-check-stack-type 'environment-pointer)
(sanity-check-stack-type 'continuation-pointer)
(sanity-check-stack-type 'backtrack-pointer)
(sanity-check-stack-type 'trail-index)
(sanity-check-stack-type 'stack-word)