Support nested LOAD

Only a few bytes saved in forth1.bin, but the DO .. LOOP construct
isn't used much yet. It's still significant savings per LOOP call.

README.md

@@ -42,8 +42,6 @@ also open `blk/000` in a modern text editor.
 
 See `/emul/README.md` for getting an emulated system running.
 
-There is also `/notes.txt` for implementation notes.
-
 ## Organisation of this repository
 
 * `forth`: Forth is slowly taking over this project (see issue #4). It comes

blk/001

@@ -1,3 +1,4 @@
 MASTER INDEX
 
-  2 Documentation
+  3 Usage                      30 Dictionary
+ 70 Implementation notes      100 Block explorer

blk/002

@@ -1,4 +0,0 @@
-Documentation index
-
-  3 Usage
- 30 Dictionary

blk/037

@@ -12,5 +12,5 @@ ALLOT    n --     Move HERE by n bytes
 C,       b --     Write byte b in HERE and advance it.
 DELW     a --     Delete wordref at a. If it shadows another
                   definition, that definition is unshadowed.
-FORGET x --       Rewind the dictionary (both CURRENT and HERE) up to
-                  x's previous entry.                   (cont.)
+EMPTY  --         Rewind HERE and CURRENT where they were at
+                  system initialization.                (cont.)

blk/038

@@ -1,5 +1,6 @@
 (cont.)
-PREV        a -- a          Return a wordref's previous entry.
-WHLEN       a -- n          Get word header length from
-                            wordref. That is, name length + 3.
-                            a is a wordref
+FORGET x --       Rewind the dictionary (both CURRENT and HERE)
+                  up to x's previous entry.             
+PREV   a -- a     Return a wordref's previous entry.
+WHLEN  a -- n     Get word header length from wordref. That is,
+                  name length + 3. a is a wordref

blk/044

@@ -1,3 +1,4 @@
 (cont.)
 UNTIL     f --         *I* Jump backwards to BEGIN if f is
                        false.
+EXIT!     --           Exit current INTERPRET loop.

blk/064

@@ -1,4 +1,6 @@
 Disk
 
+BLK> -- a Address of the current block variable.
 LIST n -- Prints the contents of the block n on screen in the
           form of 16 lines of 64 columns.
+LOAD n -- Interprets Forth code from block n

blk/070

@@ -0,0 +1,6 @@
+Implementation notes
+
+71 Execution model             73 Executing a word
+75 Stack management            77 Dictionary
+80 System variables            85 Word routines
+89 Initialization sequence

blk/071

@@ -0,0 +1,11 @@
+EXECUTION MODEL
+
+After having read a line through readln, we want to interpret
+it. As a general rule, we go like this:
+
+1. read single word from line
+2. Can we find the word in dict?
+3. If yes, execute that word, goto 1
+4. Is it a number?
+5. If yes, push that number to PS, goto 1
+6. Error: undefined word.

blk/073

@@ -0,0 +1,16 @@
+EXECUTING A WORD
+
+At it's core, executing a word is pushing the wordref on PS and
+calling EXECUTE. Then, we let the word do its things. Some
+words are special, but most of them are of the compiledWord
+type, and that's their execution that we describe here.
+
+First of all, at all time during execution, the Interpreter
+Pointer (IP) points to the wordref we're executing next.
+
+When we execute a compiledWord, the first thing we do is push
+IP to the Return Stack (RS). Therefore, RS' top of stack will
+contain a wordref to execute next, after we EXIT.
+
+At the end of every compiledWord is an EXIT. This pops RS, sets
+IP to it, and continues.

blk/075

@@ -0,0 +1,14 @@
+Stack management
+
+The Parameter stack (PS) is maintained by SP and the Return
+stack (RS) is maintained by IX. This allows us to generally use
+push and pop freely because PS is the most frequently used.
+However, this causes a problem with routine calls: because in
+Forth, the stack isn't balanced within each call, our return
+offset, when placed by a CALL, messes everything up. This is
+one of the reasons why we need stack management routines below.
+IX always points to RS' Top Of Stack (TOS)
+
+This return stack contain "Interpreter pointers", that is a
+pointer to the address of a word, as seen in a compiled list of
+words.

blk/077

@@ -0,0 +1,16 @@
+Dictionary
+
+A dictionary entry has this structure:
+
+- Xb name. Arbitrary long number of character (but can't be
+  bigger than input buffer, of course). not null-terminated
+- 2b prev offset
+- 1b size + IMMEDIATE flag
+- 2b code pointer
+- Parameter field (PF)
+
+The prev offset is the number of bytes between the prev field
+and the previous word's code pointer.
+
+The size + flag indicate the size of the name field, with the
+7th bit being the IMMEDIATE flag.                       (cont.)

blk/078

@@ -0,0 +1,10 @@
+(cont.) The code pointer point to "word routines". These
+routines expect to be called with IY pointing to the PF. They
+themselves are expected to end by jumping to the address at
+(IP). They will usually do so with "jp next".
+
+That's for "regular" words (words that are part of the dict
+chain). There are also "special words", for example NUMBER,
+LIT, FBR, that have a slightly different structure. They're
+also a pointer to an executable, but as for the other fields,
+the only one they have is the "flags" field.

blk/080

@@ -0,0 +1,16 @@
+System variables
+
+There are some core variables in the core system that are
+referred to directly by their address in memory throughout the
+code. The place where they live is configurable by the RAMSTART
+constant in conf.fs, but their relative offset is not. In fact,
+they're mostly referred to directly as their numerical offset
+along with a comment indicating what this offset refers to.
+
+This system is a bit fragile because every time we change those
+offsets, we have to be careful to adjust all system variables
+offsets, but thankfully, there aren't many system variables.
+Here's a list of them:
+
+
+                                                        (cont.)

blk/081

@@ -0,0 +1,16 @@
+(cont.)
+RAMSTART  INITIAL_SP    +53       readln's variables
++02       CURRENT       +55       adev's variables
++04       HERE          +57       blk's variables
++06       IP            +59       z80a's variables
++08       FLAGS         +5b       FUTURE USES
++0a       PARSEPTR      +70       DRIVERS
++0c       CINPTR        +80       RAMEND
++0e       WORDBUF
++2e       BOOT C< PTR
++4e       INTJUMP
++51       CURRENTPTR
+
+
+
+                                                        (cont.)

blk/082

@@ -0,0 +1,16 @@
+(cont.) INITIAL_SP holds the initial Stack Pointer value so
+that we know where to reset it on ABORT
+
+CURRENT points to the last dict entry.
+
+HERE points to current write offset.
+
+IP is the Interpreter Pointer
+
+FLAGS holds global flags. Only used for prompt output control
+for now.
+
+PARSEPTR holds routine address called on (parse)
+
+CINPTR holds routine address called on C<
+                                                        (cont.)

blk/083

@@ -0,0 +1,16 @@
+(cont.) WORDBUF is the buffer used by WORD
+
+BOOT C< PTR is used when Forth boots from in-memory
+source. See "Initialization sequence" below.
+
+INTJUMP All RST offsets (well, not *all* at this moment, I
+still have to free those slots...) in boot binaries are made to
+jump to this address. If you use one of those slots for an
+interrupt, write a jump to the appropriate offset in that RAM
+location.
+
+CURRENTPTR points to current CURRENT. The Forth CURRENT word
+doesn't return RAM+2 directly, but rather the value at this
+address. Most of the time, it points to RAM+2, but sometimes,
+when maintaining alternative dicts (during cross compilation
+for example), it can point elsewhere.                   (cont.)

blk/084

@@ -0,0 +1,6 @@
+(cont.) FUTURE USES section is unused for now.          
+
+DRIVERS section is reserved for recipe-specific
+drivers. Here is a list of known usages:
+
+* 0x70-0x78: ACIA buffer pointers in RC2014 recipes.

blk/085

@@ -0,0 +1,16 @@
+Word routines
+
+This is the description of all word routine you can encounter
+in this Forth implementation. That is, a wordref will always
+point to a memory offset containing one of these numbers.
+
+0x17: nativeWord. This words PFA contains native binary code
+and is jumped to directly.
+
+0x0e: compiledWord. This word's PFA contains an atom list and
+its execution is described in "EXECUTION MODEL" above.
+
+0x0b: cellWord. This word is usually followed by a 2-byte value
+in its PFA.  Upon execution, the *address* of the PFA is pushed
+to PS.
+                                                        (cont.)

blk/086

@@ -0,0 +1,16 @@
+(cont.)
+0x2b: doesWord. This word is created by "DOES>" and is followed
+by a 2-byte value as well as the adress where "DOES>" was
+compiled. At that address is an atom list exactly like in a
+compiled word. Upon execution, after having pushed its cell
+addr to PSP, it execute its reference exactly like a
+compiledWord.
+
+0x20: numberWord. No word is actually compiled with this
+routine, but atoms are.  Atoms with a reference to the number
+words routine are followed, *in the atom list*, of a 2-byte
+number. Upon execution, that number is fetched and IP is
+avdanced by an extra 2 bytes.
+
+0x24: addrWord. Exactly like a numberWord, except that it is
+treated differently by meta-tools.                      (cont.)

blk/087

@@ -0,0 +1,6 @@
+(cont.)
+0x22: litWord. Similar to a number word, except that instead of
+being followed by a 2 byte number, it is followed by a
+null-terminated string. Upon execution, the address of that
+null-terminated string is pushed on the PSP and IP is advanced
+to the address following the null.

blk/089

@@ -0,0 +1,16 @@
+Initialization sequence
+
+On boot, we jump to the "main" routine in boot.fs which does
+very few things.
+
+1. Set SP to 0x10000-6
+2. Sets HERE to RAMEND (RAMSTART+0x80).
+3. Sets CURRENT to value of LATEST field in stable ABI.
+4. Look for the word "BOOT" and calls it.
+
+In a normal system, BOOT is in icore and does a few things:
+
+1. Find "(parse)" and set "(parse*)" to it.
+2. Find "(c<)" a set CINPTR to it (what C< calls).
+3. Write LATEST in SYSTEM SCRATCHPAD ( see below )
+4. Find "INIT". If found, execute. Otherwise, "INTERPRET"(cont)

blk/090

@@ -0,0 +1,16 @@
+(cont.) On a bare system (only boot+icore), this sequence will
+result in "(parse)" reading only decimals and (c<) reading
+characters from memory starting from CURRENT (this is why we
+put CURRENT in SYSTEM SCRATCHPAD, it tracks current pos ).
+
+This means that you can put initialization code in source form
+right into your binary, right after your last compiled dict
+entry and it's going to be executed as such until you set a new
+(c<).
+
+Note that there is no EMIT in a bare system. You have to take
+care of supplying one before your load core.fs and its higher
+levels.
+
+
+                                                        (cont.)

blk/091

@@ -0,0 +1,7 @@
+(cont.) In the "/emul" binaries, "HERE" is readjusted to
+"CURRENT @" so that we don't have to relocate compiled dicts.
+Note that in this context, the initialization code  is fighting
+for space with HERE: New entries to the dict will overwrite
+that code!  Also, because we're barebone, we can't have
+comments. This can lead to peculiar code in this area where we
+try to "waste" space in initialization code.

blk/100

@@ -0,0 +1,10 @@
+Block explorer
+
+This is an application to conveniently browse the contents of
+the disk blocks. You can launch it with "102 LOAD".
+
+USAGE: When loaded, the Forth interpreter is replaced by the
+explorer interpreter. Typing "Q" quits the program.
+
+Typing a decimal number followed by space or return lists the
+contents of that block.

blk/102

@@ -0,0 +1,2 @@
+: foo ." Hello world! " 42 . ;
+foo

blk/103

@@ -0,0 +1 @@
+42 . 102 LOAD 43 .

emul/Makefile

@@ -20,11 +20,11 @@ BLKPACK = ../tools/blkpack
 .PHONY: all
 all: $(TARGETS)
 
-$(STRIPFC):
-$(SLATEST):
-$(BIN2C):
 $(BLKPACK):
 	$(MAKE) -C ../tools
+$(STRIPFC): $(BLKPACK)
+$(SLATEST): $(BLKPACK)
+$(BIN2C): $(BLKPACK)
 
 # z80c.bin is not in the prerequisites because it's a bootstrap
 # binary that should be updated manually through make updatebootstrap.
@@ -77,5 +77,5 @@ updatebootstrap: forth/stage2
 
 .PHONY: clean
 clean:
-	rm -f $(TARGETS) emul.o forth/*-bin.h forth/forth?.bin
+	rm -f $(TARGETS) emul.o forth/*-bin.h forth/forth?.bin blkfs
 	$(MAKE) -C ../tools clean

emul/forth/run.fs

@@ -11,5 +11,6 @@
     ['] EFS@ BLK@* !
     RDLN$
     Z80A$
+    LIT< _sys [entry]
     INTERPRET
 ;

forth/blk.fs

@@ -11,7 +11,11 @@
 
 : BLK$
     H@ 0x57 RAM+ !
+    ( 1024 for the block, 6 for variables )
     1030 ALLOT
+    ( LOAD detects end of block with ASCII EOT. This is why
+      we write it there. EOT == 0x04 )
+    4 C,
     -1 BLK> !
 ;
 
@@ -30,3 +34,39 @@
         CRLF
     LOOP
 ;
+
+: _
+    (boot<)
+    DUP 4 = IF
+        DROP
+        ( We're finished interpreting )
+        EXIT!
+    THEN
+;
+
+: LOAD
+    ( save BLK>, CINPTR and boot< ptr to RSP )
+    BLK> @ >R
+    0x0c RAM+ @ >R
+    0x2e RAM+ @ >R
+    BLK@
+    ( Point to beginning of BLK )
+    BLK( 0x2e RAM+ !
+    ( 0c == CINPTR )
+    ['] _ 0x0c RAM+ !
+    INTERPRET
+    R> 0x2e RAM+ !
+    ( Before we restore CINPTR, are we restoring it to "_"?
+      if yes, it means we're in a nested LOAD which means we
+      should also load back the saved BLK>. Otherwise, we can
+      ignore the BLK> from RSP. )
+    I 0x0c RAM+ @ = IF
+        ( nested load )
+        R> DROP ( CINPTR )
+        R> BLK@
+    ELSE
+        ( not nested )
+        R> 0x0c RAM+ !
+        R> DROP ( BLK> )
+    THEN
+;

forth/core.fs

@@ -94,12 +94,20 @@
     H@
 ; IMMEDIATE
 
+( Increase loop counter and returns whether we should loop. )
+: _
+    R>          ( IP, keep for later )
+    R> 1 +      ( ip i+1 )
+    DUP >R      ( ip i )
+    I' =        ( ip f )
+    SWAP >R     ( f )
+;
+
 ( One could think that we should have a sub word to avoid all
   these COMPILE, but we can't because otherwise it messes with
   the RS )
 : LOOP
-    COMPILE R> 1 LITN COMPILE + COMPILE DUP COMPILE >R
-    COMPILE I' COMPILE = COMPILE (?br)
+    COMPILE _ COMPILE (?br)
     H@ - ,
     COMPILE R> COMPILE DROP COMPILE R> COMPILE DROP
 ; IMMEDIATE
@@ -136,3 +144,17 @@
     DUP WHLEN - HERE !  ( w )
     PREV CURRENT !
 ;
+
+: EMPTY
+    LIT< _sys (find) NOT IF ABORT THEN
+    DUP HERE ! CURRENT !
+;
+
+( Drop RSP until I-2 == INTERPRET. )
+: EXIT!
+    ['] INTERPRET       ( I )
+    BEGIN               ( I )
+    DUP                 ( I I )
+    R> DROP I 2 - @     ( I I a )
+    = UNTIL
+;

forth/icore.fs

@@ -146,10 +146,9 @@
     AGAIN
 ;
 
-: (entry)
-    HERE @    ( h )
-    WORD         ( h s )
-    SCPY         ( h )
+: [entry]
+    HERE @       ( w h )
+    SWAP SCPY    ( h )
     ( Adjust HERE -1 because SCPY copies the null )
     HERE @ 1 - ( h h' )
     DUP HERE ! ( h h' )
@@ -161,6 +160,8 @@
     HERE @ CURRENT !
 ;
 
+: (entry) WORD [entry] ;
+
 : INTERPRET
     BEGIN
     WORD
@@ -177,7 +178,7 @@
 
 ( system c< simply reads source from binary, starting at
   LATEST. Convenient way to bootstrap a new system. )
-: (c<)
+: (boot<)
     ( 2e == BOOT C< PTR )
     0x2e RAM+ @   ( a )
     DUP C@        ( a c )
@@ -191,7 +192,7 @@
     ( 2e == SYSTEM SCRATCHPAD )
     CURRENT @ 0x2e RAM+ !
     ( 0c == CINPTR )
-    LIT< (c<) (find) DROP 0x0c RAM+ !
+    LIT< (boot<) (find) DROP 0x0c RAM+ !
     LIT< INIT (find)
     IF EXECUTE
     ELSE DROP INTERPRET THEN

notes.txt

@@ -1,203 +0,0 @@
-Collapse OS' Forth implementation notes
-
-*** EXECUTION MODEL
-
-After having read a line through readln, we want to interpret it. As a general
-rule, we go like this:
-
-1. read single word from line
-2. Can we find the word in dict?
-3. If yes, execute that word, goto 1
-4. Is it a number?
-5. If yes, push that number to PS, goto 1
-6. Error: undefined word.
-
-*** EXECUTING A WORD
-
-At it's core, executing a word is pushing the wordref on PS and calling EXECUTE.
-Then, we let the word do its things. Some words are special, but most of them
-are of the compiledWord type, and that's their execution that we describe here.
-
-First of all, at all time during execution, the Interpreter Pointer (IP) points
-to the wordref we're executing next.
-
-When we execute a compiledWord, the first thing we do is push IP to the Return
-Stack (RS). Therefore, RS' top of stack will contain a wordref to execute next,
-after we EXIT.
-
-At the end of every compiledWord is an EXIT. This pops RS, sets IP to it, and
-continues.
-
-*** Stack management
-
-The Parameter stack (PS) is maintained by SP and the Return stack (RS) is
-maintained by IX. This allows us to generally use push and pop freely because PS
-is the most frequently used. However, this causes a problem with routine calls:
-because in Forth, the stack isn't balanced within each call, our return offset,
-when placed by a CALL, messes everything up. This is one of the reasons why we
-need stack management routines below. IX always points to RS' Top Of Stack (TOS)
-
-This return stack contain "Interpreter pointers", that is a pointer to the
-address of a word, as seen in a compiled list of words.
-
-*** Dictionary
-
-A dictionary entry has this structure:
-
-- Xb name. Arbitrary long number of character (but can't be bigger than
-  input buffer, of course). not null-terminated
-- 2b prev offset
-- 1b size + IMMEDIATE flag
-- 2b code pointer
-- Parameter field (PF)
-
-The prev offset is the number of bytes between the prev field and the previous
-word's code pointer.
-
-The size + flag indicate the size of the name field, with the 7th bit being the
-IMMEDIATE flag.
-
-The code pointer point to "word routines". These routines expect to be called
-with IY pointing to the PF. They themselves are expected to end by jumping to
-the address at (IP). They will usually do so with "jp next".
-
-That's for "regular" words (words that are part of the dict chain). There are
-also "special words", for example NUMBER, LIT, FBR, that have a slightly
-different structure. They're also a pointer to an executable, but as for the
-other fields, the only one they have is the "flags" field.
-
-*** System variables
-
-There are some core variables in the core system that are referred to directly
-by their address in memory throughout the code. The place where they live is
-configurable by the RAMSTART constant in conf.fs, but their relative offset is
-not. In fact, they're mostly referred to directly as their numerical offset
-along with a comment indicating what this offset refers to.
-
-This system is a bit fragile because every time we change those offsets, we
-have to be careful to adjust all system variables offsets, but thankfully,
-there aren't many system variables. Here's a list of them:
-
-RAMSTART   INITIAL_SP
-+02        CURRENT
-+04        HERE
-+06        IP
-+08        FLAGS
-+0a        PARSEPTR
-+0c        CINPTR
-+0e        WORDBUF
-+2e        BOOT C< PTR
-+4e        INTJUMP
-+51        CURRENTPTR
-+53        readln's variables
-+55        adev's variables
-+57        blk's variables
-+59        z80a's variables
-+5b        FUTURE USES
-+70        DRIVERS
-+80        RAMEND
-
-INITIAL_SP holds the initial Stack Pointer value so that we know where to reset
-it on ABORT
-
-CURRENT points to the last dict entry.
-
-HERE points to current write offset.
-
-IP is the Interpreter Pointer
-
-FLAGS holds global flags. Only used for prompt output control for now.
-
-PARSEPTR holds routine address called on (parse)
-
-CINPTR holds routine address called on C<
-
-WORDBUF is the buffer used by WORD
-
-BOOT C< PTR is used when Forth boots from in-memory source. See "Initialization
-sequence" below.
-
-INTJUMP All RST offsets (well, not *all* at this moment, I still have to free
-those slots...) in boot binaries are made to jump to this address. If you use
-one of those slots for an interrupt, write a jump to the appropriate offset in
-that RAM location.
-
-CURRENTPTR points to current CURRENT. The Forth CURRENT word doesn't return
-RAM+2 directly, but rather the value at this address. Most of the time, it
-points to RAM+2, but sometimes, when maintaining alternative dicts (during
-cross compilation for example), it can point elsewhere.
-
-FUTURE USES section is unused for now.
-
-DRIVERS section is reserved for recipe-specific drivers. Here is a list of
-known usages:
-
-* 0x70-0x78: ACIA buffer pointers in RC2014 recipes.
-
-*** Word routines
-
-This is the description of all word routine you can encounter in this Forth
-implementation. That is, a wordref will always point to a memory offset
-containing one of these numbers.
-
-0x17: nativeWord. This words PFA contains native binary code and is jumped to
-directly.
-
-0x0e: compiledWord. This word's PFA contains an atom list and its execution is
-described in "EXECUTION MODEL" above.
-
-0x0b: cellWord. This word is usually followed by a 2-byte value in its PFA.
-Upon execution, the *address* of the PFA is pushed to PS.
-
-0x2b: doesWord. This word is created by "DOES>" and is followed by a 2-byte
-value as well as the adress where "DOES>" was compiled. At that address is an
-atom list exactly like in a compiled word. Upon execution, after having pushed
-its cell addr to PSP, it execute its reference exactly like a compiledWord.
-
-0x20: numberWord. No word is actually compiled with this routine, but atoms are.
-Atoms with a reference to the number words routine are followed, *in the atom
-list*, of a 2-byte number. Upon execution, that number is fetched and IP is
-avdanced by an extra 2 bytes.
-
-0x24: addrWord. Exactly like a numberWord, except that it is treated
-differently by meta-tools.
-
-0x22: litWord. Similar to a number word, except that instead of being followed
-by a 2 byte number, it is followed by a null-terminated string. Upon execution,
-the address of that null-terminated string is pushed on the PSP and IP is
-advanced to the address following the null.
-
-*** Initialization sequence
-
-On boot, we jump to the "main" routine in boot.fs which does very few things.
-
-1. Set SP to 0x10000-6
-2. Sets HERE to RAMEND (RAMSTART+0x80).
-3. Sets CURRENT to value of LATEST field in stable ABI.
-4. Look for the word "BOOT" and calls it.
-
-In a normal system, BOOT is in icore and does a few things:
-
-1. Find "(parse)" and set "(parse*)" to it.
-2. Find "(c<)" a set CINPTR to it (what C< calls).
-3. Write LATEST in SYSTEM SCRATCHPAD ( see below )
-4. Find "INIT". If found, execute. Otherwise, execute "INTERPRET"
-
-On a bare system (only boot+icore), this sequence will result in "(parse)"
-reading only decimals and (c<) reading characters from memory starting from
-CURRENT (this is why we put CURRENT in SYSTEM SCRATCHPAD, it tracks current
-pos ).
-
-This means that you can put initialization code in source form right into your
-binary, right after your last compiled dict entry and it's going to be executed
-as such until you set a new (c<).
-
-Note that there is no EMIT in a bare system. You have to take care of supplying
-one before your load core.fs and its higher levels.
-
-In the "/emul" binaries, "HERE" is readjusted to "CURRENT @" so that we don't
-have to relocate compiled dicts. Note that in this context, the initialization
-code  is fighting for space with HERE: New entries to the dict will overwrite
-that code! Also, because we're barebone, we can't have comments. This can lead
-to peculiar code in this area where we try to "waste" space in initialization
-code.