X-Git-Url: https://git.rrq.au/?a=blobdiff_plain;f=main.asm;h=183be74435f3b7091edd50c08ce92d3076434640;hb=412aa1087846d432ddc5bb93c3dcb2acf292010c;hp=21a911cf164675d6dba7fc201559d3c77fdb43a3;hpb=2cd770b4f9a46cbc7ff07b26f4851bba1ea36a7d;p=rrq%2Fjonasforth.git

diff --git a/main.asm b/main.asm
index 21a911c..183be74 100644
--- a/main.asm
+++ b/main.asm
@@ -242,6 +242,55 @@ forth HELLO, 'HELLO'
   dq NEWLINE
   dq EXIT
 
+;; Duplicate a pair of elements.
+forth_asm PAIRDUP, '2DUP'
+  pop rbx
+  pop rax
+  push rax
+  push rbx
+  push rax
+  push rbx
+  next
+
+;; Swap the top two elements on the stack.
+forth_asm SWAP, 'SWAP'
+  pop rax
+  pop rbx
+  push rax
+  push rbx
+  next
+
+;; Remove the top element from the stack.
+forth_asm DROP, 'DROP'
+  add rsp, 8
+  next
+
+;; The INTERPRET word reads and interprets user input. It's behavior depends on
+;; the current STATE. It provides special handling for integers. (TODO)
+forth INTERPRET, 'INTERPRET'
+  ;; Read word
+  dq READ_WORD
+  dq PAIRDUP
+  ;; Stack is (word length word length).
+  dq FIND                       ; Try to find word
+  dq DUP_
+  dq ZBRANCH, 8 * 8             ; Check if word is found
+
+  ;; Word is found, execute it
+  dq TCFA
+  ;; Stack is (word length addr)
+  dq SWAP, DROP
+  dq SWAP, DROP
+  ;; Stack is (addr)
+  dq EXEC
+  dq EXIT
+
+  ;; No word is found, assume it is an integer literal
+  ;; Stack is (word length addr)
+  dq DROP
+  dq PARSE_NUMBER
+  dq EXIT
+
 ;; .U prints the value on the stack as an unsigned integer in hexadecimal.
 forth_asm DOTU, '.U'
   mov [.length], 0
@@ -303,16 +352,40 @@ forth_asm DOTU, '.U'
   pop rsi
   next
 
+;; Takes a value and an address, and stores the value at the given address.
+forth_asm PUT, '!'
+  pop rbx                       ; Address
+  pop rax                       ; Value
+  mov [rbx], rax
+  next
+
+;; Takes an address and returns the value at the given address.
+forth_asm GET, '@'
+  pop rax
+  mov rax, [rax]
+  push rax
+  next
+
+;; Get the location of the STATE variable. It can be set with '!' and read with
+;; '@'.
+forth STATE, 'STATE'
+  dq LIT, var_STATE
+  dq EXIT
+
 forth MAIN, 'MAIN'
   dq HELLO
-  dq READ_WORD, FIND, TCFA, EXEC
-  dq BRANCH, -8 * 5
+  dq INTERPRET
+  dq BRANCH, -8 * 2
   dq TERMINATE
 
 segment readable writable
 
 latest_entry dq initial_latest_entry
 
+;; The STATE variable is 0 when the interpreter is executing, and non-zero when
+;; it is compiling.
+var_STATE dq 0
+
 FIND.rsi dq ?
 
 READ_WORD.rsi dq ?