Implement '!' and '@' commands and add 'STATE' variable

[rrq/jonasforth.git] / main.asm

diff --git a/main.asm b/main.asm
index 21a911cf164675d6dba7fc201559d3c77fdb43a3..edcba0ae9421c712218041e64d4fc0872370f8d9 100644 (file)
--- a/main.asm
+++ b/main.asm
@@ -242,6 +242,15 @@ forth HELLO, 'HELLO'
   dq NEWLINE
   dq EXIT
 
+;; 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'
+  dq READ_WORD
+  dq FIND
+  dq TCFA
+  dq EXEC
+  dq EXIT
+
 ;; .U prints the value on the stack as an unsigned integer in hexadecimal.
 forth_asm DOTU, '.U'
   mov [.length], 0
@@ -303,16 +312,40 @@ 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 ?