From: Jonas Hvid <mail@johv.dk>
Date: Fri, 6 Dec 2019 12:30:54 +0000 (+0100)
Subject: Add variables 'LATEST' and 'HERE'
X-Git-Url: https://git.rrq.au/?a=commitdiff_plain;h=623eb650651ba4105e4e91239c52b04ed0e5cd85;p=rrq%2Fjonasforth.git

Add variables 'LATEST' and 'HERE'

These will be used for compilation.
---

diff --git a/main.asm b/main.asm
index 183be74..cbf8a13 100644
--- a/main.asm
+++ b/main.asm
@@ -372,6 +372,19 @@ forth STATE, 'STATE'
   dq LIT, var_STATE
   dq EXIT
 
+;; Get the location of the LATEST variable. It can be set with '!' and read with
+;; '@'.
+forth LATEST, 'LATEST'
+  dq LIT, latest_entry
+  dq EXIT
+
+;; Get the location at which compiled words are expected to be added. This
+;; pointer is usually modified automatically when calling ',', but we can also
+;; read it manually with 'HERE'.
+forth HERE, 'HERE'
+  dq LIT, here
+  dq EXIT
+
 forth MAIN, 'MAIN'
   dq HELLO
   dq INTERPRET
@@ -380,6 +393,9 @@ forth MAIN, 'MAIN'
 
 segment readable writable
 
+;; The LATEST variable holds a pointer to the word that was last added to the
+;; dictionary. This pointer is updated as new words are added, and its value is
+;; used by FIND to look up words.
 latest_entry dq initial_latest_entry
 
 ;; The STATE variable is 0 when the interpreter is executing, and non-zero when
@@ -397,6 +413,10 @@ DOTU.rbuffer rq 16
 DOTU.length dq ?
 DOTU.printed_length dq ?
 
+;; Reserve space for compiled words, accessed through HERE.
+here dq here_top
+here_top rq $2000
+
 ;; Return stack
 rq $2000
 return_stack_top: