--- /dev/null
+;; vim: syntax=fasm
+
+;; We need some basic words to be available before we can implement the actual
+;; interpreter. For this reason we need to write some words in assembly, even
+;; though they depend only on other Forth words. Such words are defined in this
+;; file.
+;;
+;; With these words, we can finally defined INTERPRET, and from there we'll load
+;; everything else from an external file.
+;;
+;; This file is included from main.asm; see that file for more information.
+
+;; Define a Forth word that is implemented in Forth. (The body will be a list of
+;; 'dq' statements.)
+macro forth label, name, immediate {
+ header label, name, immediate
+ dq DOCOL
+}
+
+forth COMMA, ','
+ dq HERE, GET, PUT ; Set the memory at the address pointed to by HERE
+ dq HERE, GET, LIT, 8, PLUS ; Calculate new address for HERE to point to
+ dq HERE, PUT ; Update HERE to point to the new address
+ dq EXIT
+
+;; Mark the last added word as immediate.
+forth IMMEDIATE, 'IMMEDIATE', 1
+ dq LIT, 1
+ dq LATEST, GET
+ dq LIT, 8, PLUS
+ dq PUT_BYTE
+ dq EXIT
+
+;; Given the address of a word, return 0 if the given word is not immediate.
+forth IS_IMMEDIATE, 'IMMEDIATE?'
+ dq LIT, 8, PLUS
+ dq GET_BYTE
+ dq EXIT
+
+;; Enter immediate mode, immediately
+forth INTO_IMMEDIATE, '[', 1
+ dq LIT, 0, STATE, PUT_BYTE
+ dq EXIT
+
+;; Enter compilation mode
+forth OUTOF_IMMEDIATE, ']'
+ dq LIT, 1, STATE, PUT_BYTE
+ dq EXIT
+
+;; The INTERPRET word reads and interprets user input. It's behavior depends on
+;; the current STATE. It provides special handling for integers.
+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 * 22 ; Check if word is found
+
+ ;; - Word is found -
+
+ dq STATE, GET, ZBRANCH, 8 * 11 ; Check whether we are in compilation or immediate mode
+
+ ;; (Word found, compilation mode)
+ dq DUP_, IS_IMMEDIATE, NOT_, ZBRANCH, 8 * 6 ; If the word is immediate, continue as we would in immediate mode
+
+ ;; Otherwise, we want to compile this word
+ dq TCFA
+ dq COMMA
+ dq DROP, DROP
+ dq EXIT
+
+ ;; (Word found, immediate mode)
+ ;; Execute word
+ 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 STATE, GET, ZBRANCH, 8 * 5 ; Check whether we are in compilation or immediate mode
+
+ ;; (Number, compilation mode)
+ dq LIT, LIT, COMMA
+ dq COMMA
+ dq EXIT
+
+ ;; (Number, immediate mode)
+ dq EXIT
.start:
}
-;; Define a Forth word that is implemented in Forth. (The body will be a list of
-;; 'dq' statements.)
-macro forth label, name, immediate {
- header label, name, immediate
- dq DOCOL
-}
-
segment readable executable
entry main
-include "impl.asm"
+include "impl.asm" ; Misc. subroutines
+include "bootstrap.asm" ; Forth words encoded in Assembly
main:
cld ; Clear direction flag so LODSQ does the right thing.
popr rsi
next
-;; Prints a newline to standard output.
-forth NEWLINE, 'NEWLINE'
- dq LIT, $A
- dq EMIT
- dq EXIT
-
-;; Prints a space to standard output.
-forth SPACE, 'SPACE'
- dq LIT, ' '
- dq EMIT
- dq EXIT
-
;; Read a word from standard input and push it onto the stack as a pointer and a
;; size. The pointer is valid until the next call to READ_WORD.
forth_asm READ_WORD, 'READ-WORD'
push rax ; Result
next
-forth READ_NUMBER, 'READ-NUMBER'
- dq READ_WORD
- dq PARSE_NUMBER
- dq EXIT
-
;; Takes a string (in the form of a pointer and a length on the stack) and
;; prints it to standard output.
forth_asm TELL, 'TELL'
push 1
next
-;; The INTERPRET word reads and interprets user input. It's behavior depends on
-;; the current STATE. It provides special handling for integers.
-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 * 22 ; Check if word is found
-
- ;; - Word is found -
-
- dq STATE, GET, ZBRANCH, 8 * 11 ; Check whether we are in compilation or immediate mode
-
- ;; (Word found, compilation mode)
- dq DUP_, IS_IMMEDIATE, NOT_, ZBRANCH, 8 * 6 ; If the word is immediate, continue as we would in immediate mode
-
- ;; Otherwise, we want to compile this word
- dq TCFA
- dq COMMA
- dq DROP, DROP
- dq EXIT
-
- ;; (Word found, immediate mode)
- ;; Execute word
- 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 STATE, GET, ZBRANCH, 8 * 5 ; Check whether we are in compilation or immediate mode
-
- ;; (Number, compilation mode)
- dq LIT, LIT, COMMA
- dq COMMA
- dq EXIT
-
- ;; (Number, immediate mode)
- dq EXIT
-
;; .U prints the value on the stack as an unsigned integer in hexadecimal.
forth_asm DOTU, '.U'
mov [.length], 0
push rdx ; a % b
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
-
-;; 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 COMMA, ','
- dq HERE, GET, PUT ; Set the memory at the address pointed to by HERE
- dq HERE, GET, LIT, 8, PLUS ; Calculate new address for HERE to point to
- dq HERE, PUT ; Update HERE to point to the new address
- dq EXIT
-
;; Read user input until next " character is found. Push a string containing the
;; input on the stack as (buffer length). Note that the buffer is only valid
;; until the next call to S" and that no more than 255 character can be read.
next
-;; Mark the last added word as immediate.
-forth IMMEDIATE, 'IMMEDIATE', 1
- dq LIT, 1
- dq LATEST, GET
- dq LIT, 8, PLUS
- dq PUT_BYTE
- dq EXIT
-
-;; Given the address of a word, return 0 if the given word is not immediate.
-forth IS_IMMEDIATE, 'IMMEDIATE?'
- dq LIT, 8, PLUS
- dq GET_BYTE
- dq EXIT
-
-;; Enter immediate mode, immediately
-forth INTO_IMMEDIATE, '[', 1
- dq LIT, 0, STATE, PUT_BYTE
- dq EXIT
-
-;; Enter compilation mode
-forth OUTOF_IMMEDIATE, ']'
- dq LIT, 1, STATE, PUT_BYTE
- dq EXIT
-
forth_asm TICK, "'"
lodsq
push rax
dq BRANCH, -8 * 2
dq TERMINATE
+;; Built-in variables:
+
+forth STATE, 'STATE'
+ dq LIT, var_STATE
+ dq EXIT
+
+forth LATEST, 'LATEST'
+ dq LIT, latest_entry
+ dq EXIT
+
+forth HERE, 'HERE'
+ dq LIT, here
+ dq EXIT
+
segment readable writable
;; The LATEST variable holds a pointer to the word that was last added to the
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