implement LEAVE, [IF]…[ELSE]…[THEN], and various other changes

jumpforth.S

@@ -237,7 +237,7 @@ defconst SYS_GETPID,__NR_getpid
 defconst SYS_BRK,__NR_brk
 /* defconst SYS_SIGNAL,__NR_signal */
 /* defconst SYS_UMOUNT2,__NR_umount2 */
-/* defconst SYS_IOCTL,__NR_ioctl */
+defconst SYS_IOCTL,__NR_ioctl
 /* defconst SYS_SETPGID,__NR_setpgid */
 /* defconst SYS_UMASK,__NR_umask */
 /* defconst SYS_CHROOT,__NR_chroot */
@@ -1226,6 +1226,14 @@ defcode DECREMENT,"-!"
    subl %eax,(%ebx)
    NEXT
 
+/* ( x1 a-addr -- x2 ) Store x1 in the cell at a-addr and return the old value */
+defcode XCHG
+   pop %eax
+   mov (%eax),%ebx
+   popl (%eax)
+   push %ebx
+   NEXT
+
 defcode TWOSTORE,"2!"
    pop %ebx
    popl (%ebx)
@@ -1238,6 +1246,18 @@ defcode TWOFETCH,"2@"
    pushl (%ebx)
    NEXT
 
+/* ( xd1 a-addr -- xd2 ) Store xd1 in the double-cell a-addr; return the old value */
+/* Equivalent to: DUP 2@ 2>R 2! 2R> */
+defcode TWOXCHG,"2XCHG"
+   pop %eax
+   mov 4(%eax),%ebx
+   mov (%eax),%ecx
+   popl (%eax)
+   popl 4(%eax)
+   push %ebx
+   push %ecx
+   NEXT
+
 /* ( c-addr u char -- ) Fill u characters starting at c-addr with char */
 defcode FILL
    pop %eax

startup.4th

@@ -90,7 +90,7 @@ DEFER THROW-UNWIND ( k*x n -- i*x <noreturn> )
    SP@ 2DUP C! STDOUT SWAP 1 SYS_WRITE SYSCALL3 2DROP ;
 
 \ Decrement the array size and increment the address by the same amount
-: DROP-PREFIX ( c-addr u1 u2 -- c-addr+u2 u1-u2 ) TUCK - -ROT + SWAP ;
+: /STRING ( c-addr u1 u2 -- c-addr+u2 u1-u2 ) TUCK - -ROT + SWAP ;
 
 \ Write a character array to the given file descriptor
 \ Repeat write syscall until entire string is written
@@ -106,7 +106,7 @@ DEFER THROW-UNWIND ( k*x n -- i*x <noreturn> )
             2DROP RDROP EXIT
          THEN
       ELSE
-         DROP-PREFIX
+         /STRING
       THEN
    REPEAT
    DROP RDROP ;
@@ -192,12 +192,19 @@ DEFER THROW-UNWIND ( k*x n -- i*x <noreturn> )
 \ Here this is just a LF (Unix convention) but it could be CR (Mac) or CR+LF (DOS)
 : EOL ( -- "<eol>" ) LF EMIT ;
 
+\ Emit n blank (space) characters
+: SPACES ( n -- "<spaces>" ) BEGIN ?DUP WHILE 1- SPACE REPEAT ;
+
 \ Terminate the program, successfully
 \ This will never return, even if the system call does
 : BYE ( -- <noreturn> )
    BEGIN 0 SYS_EXIT SYSCALL1 DROP AGAIN ;
 
+\ With 32-bit cells, a double-cell number has 64 bits
+\ Space is reserved for binary output with a leading minus sign and a trailing space
+\ The minimum pictured numeric output buffer size is thus 66 bytes
 80 CONSTANT PNO-BUFFER-BYTES
+
 CREATE PNO-BUFFER PNO-BUFFER-BYTES ALLOT
 PNO-BUFFER PNO-BUFFER-BYTES + CONSTANT PNO-BUFFER-END
 CREATE PNO-POINTER PNO-BUFFER-END ,
@@ -213,11 +220,7 @@ CREATE PNO-POINTER PNO-BUFFER-END ,
 : SIGN ( n -- ) 0< IF [CHAR] - HOLD THEN ;
 
 : #B ( ud1 u -- ud2 )
-   UM/MOD ROT DUP 10 >= IF
+   UM/MOD ROT DUP 10 >= IF 10 - [CHAR] A + ELSE [CHAR] 0 + THEN HOLD ;
-      10 - [CHAR] A +
-   ELSE
-      [CHAR] 0 +
-   THEN HOLD ;
 
 : # ( ud1 -- ud2 ) 10 #B ;
 
@@ -234,22 +237,26 @@ CREATE PNO-POINTER PNO-BUFFER-END ,
 : D. ( d -- "<minus?><digits>" ) DUP -ROT DABS <# #S ROT SIGN #> TYPE ;
 : . ( n -- "<minus?><digits>" ) S>D D. ;
 
+\ Return the number of words on the data and return stacks, respectively
+: DEPTH ( -- n ) SP@ S0 SWAP - CELL / ;
+: RDEPTH ( -- n ) RSP@ CELL+ R0 SWAP - CELL / ;
+
+CREATE DISPLAY-ITEM-LIMIT 6 ,
+
 \ Display the content of the data stack
-: .DS ( -- "<text>" )
+: .S ( -- "<text>" )
-   SP@ S0
+   "S(" TYPE DEPTH . "):" TYPE
-   CELL - 2DUP > IF 2DROP EXIT THEN DUP @ .
+   SP@ DUP DISPLAY-ITEM-LIMIT @ CELLS+ S0 UMIN
-   BEGIN
+   DUP S0 <> IF " …" TYPE THEN
-      CELL - 2DUP > IF 2DROP EXIT THEN DUP @ SPACE .
+   BEGIN 2DUP < WHILE CELL- DUP @ SPACE . REPEAT 2DROP EOL ;
-   AGAIN ;
 
 \ Display the content of the return stack
 : .RS ( -- "<text>" )
    \ Skip the topmost cell, which is the return address for the call to .RS
-   RSP@ CELL + R0
+   "R(" TYPE RDEPTH 1- . "):" TYPE
-   CELL - 2DUP > IF 2DROP EXIT THEN DUP @ .
+   RSP@ CELL+ DUP DISPLAY-ITEM-LIMIT @ CELLS+ R0 UMIN
-   BEGIN
+   DUP R0 <> IF " …" TYPE THEN
-      CELL - 2DUP > IF 2DROP EXIT THEN DUP @ SPACE .
+   BEGIN 2DUP < WHILE CELL- DUP @ SPACE . REPEAT 2DROP EOL ;
-   AGAIN ;
 
 \ Return the next address in the compilation/data area
 : HERE ( -- addr ) CP @ ;
@@ -315,7 +322,7 @@ CREATE PNO-POINTER PNO-BUFFER-END ,
 \ Our first control-flow primitive: <cond> IF <true> {ELSE <false>} THEN
 \
 \ IF compiles an unresolved conditional branch.
-\ AHEAD compiles an unconditional branch (same effect as TRUE IF).
+\ AHEAD compiles an unconditional branch (same effect as FALSE IF).
 \ Both AHEAD and IF leave the address of the unresolved offset on the stack.
 \
 \ THEN consumes the offset address and resolves it to the next code address.
@@ -323,12 +330,35 @@ CREATE PNO-POINTER PNO-BUFFER-END ,
 \ ELSE inserts an unconditional branch (to THEN) and also resolves the
 \ previous forward reference (from IF).
 \
-: IF ( C: -- orig ) ( Runtime S: flag -- ) IMMEDIATE
+\ Via ONWARD-IF and ONWARD-AHEAD the unresolve branch offset cell may be used
-   POSTPONE 0BRANCH HERE 0 , ;
+\ as the link field of a linked list to connect multiple forward branches to
-: AHEAD ( C: -- orig ) IMMEDIATE
+\ the same THEN. When THEN is executed it will follow the links and update all
-   POSTPONE BRANCH HERE 0 , ;
+\ the connected branches to the same location. The list is terminated with zero
+\ in the link field. Example:
+\
+\   \ The IF and ONWARD-IF both branch to <code2> if the condition is false
+\   \ This is functionally a short-circuit AND condition
+\   \ Without the ELSE they would both branch to <code3>
+\   <cond1> IF <cond2> ONWARD-IF <code1> ELSE <code2> THEN <code3>
+\
+\ ALWAYS is provided as a placeholder; it has the same effect as TRUE IF but
+\ includes no branch. The "orig" value it leaves on the stack (zero) is ignored
+\ by THEN and marks the end of the list if consumed by ONWARD-IF or ONWARD-AHEAD.
+\ This can be used as a base for control structures with zero or more branches.
+\
+\ The low-level primitives:
+: ALWAYS ( C: -- orig ) IMMEDIATE 0 ;
+: ONWARD-IF ( C: orig1 -- orig2 ) IMMEDIATE
+   POSTPONE 0BRANCH HERE SWAP , ;
+: ONWARD-AHEAD ( C: orig1 -- orig2 ) IMMEDIATE
+   POSTPONE BRANCH HERE SWAP , ;
 : THEN ( C: orig -- ) IMMEDIATE
-   HERE OVER - SWAP ! ;
+   BEGIN ?DUP WHILE HERE OVER - SWAP XCHG REPEAT ;
+\ The derived control structures:
+: IF ( C: -- orig ) ( Runtime S: flag -- ) IMMEDIATE
+   POSTPONE ALWAYS POSTPONE ONWARD-IF ;
+: AHEAD ( C: -- orig ) IMMEDIATE
+   POSTPONE ALWAYS POSTPONE ONWARD-AHEAD ;
 : ELSE ( C: orig1 -- orig2 ) IMMEDIATE
    POSTPONE AHEAD SWAP POSTPONE THEN ;
 
@@ -372,38 +402,65 @@ CREATE PNO-POINTER PNO-BUFFER-END ,
 \ with the number of references on top. Inside OF ... ENDOF there is additionally
 \ a forward reference to the ENDOF (as with IF ... THEN) above the ENDCASE counter.
 \
-\ Begin by creating a counter for the number of unresolved ENDOF forward references
+\ Begin by creating a placeholder for the unresolved ENDOF forward references
 : CASE ( C: -- 0 ) IMMEDIATE
-   0 ;
+   POSTPONE ALWAYS ;
 \ At runtime compare the values on the top of the stack; branch to ENDOF if unequal
 \ Keep the first value for the next OF if unequal, otherwise consume both
 : OF ( C: orign ... orig1 n -- orign ... orig1 n orig-of ) IMMEDIATE
    POSTPONE OVER POSTPONE = POSTPONE IF POSTPONE DROP ;
 \ Create a forward branch to ENDCASE and resolve the one from OF
-: ENDOF ( C: orign ... orig1 n orig-of -- orign ... orig1 orig0 n+1 ) IMMEDIATE
+: ENDOF ( C: orig-case1 orig-of -- orig-case2 ) IMMEDIATE
-   POSTPONE AHEAD -ROT POSTPONE THEN 1+ ;
+   SWAP POSTPONE ONWARD-AHEAD SWAP POSTPONE THEN ;
 \ Drop the <x> value in case none of the OF...ENDOF clauses matched
 \ Resolve all the forward branches from ENDOF to the location after ENDCASE
-: ENDCASE ( C: orign ... orig1 n -- ) IMMEDIATE
+: ENDCASE ( C: orig-case -- ) IMMEDIATE
-   POSTPONE DROP BEGIN ?DUP WHILE 1- SWAP POSTPONE THEN REPEAT ;
+   POSTPONE DROP POSTPONE THEN ;
 
 \ Range loop: <limit> <index> DO <code> LOOP
 \             <limit> <index> DO <code> <step> +LOOP
-: UNLOOP POSTPONE 2RDROP ; IMMEDIATE
+\             <limit> <index> ?DO <code> LOOP
-: DO POSTPONE 2>R POSTPONE BEGIN ; IMMEDIATE
+\             <limit> <index> ?DO <code> <step> +LOOP
-: (+LOOP) ( step limit index -- flag limit index' )
+CREATE LEAVE-ORIG 0 ,
-   ROT + 2DUP = -ROT ;
+: DO ( C: -- outer-stack dest S: limit index R: -- limit index ) IMMEDIATE
-: +LOOP IMMEDIATE
+   POSTPONE 2>R LEAVE-ORIG @
-   POSTPONE 2R> POSTPONE (+LOOP) POSTPONE 2>R
+   POSTPONE ALWAYS LEAVE-ORIG !
-   POSTPONE UNTIL POSTPONE 2RDROP ;
+   POSTPONE BEGIN ;
-' (+LOOP) (HIDE)
+: ?DO ( C: -- outer-stack dest S: limit index R: -- limit index ) IMMEDIATE
-: LOOP IMMEDIATE 1 POSTPONE LITERAL POSTPONE +LOOP ;
+   POSTPONE 2>R LEAVE-ORIG @
+   POSTPONE 2R@ POSTPONE <> POSTPONE IF LEAVE-ORIG !
+   POSTPONE BEGIN ;
+: LEAVE ( C: -- S: -- R: limit index -- ) IMMEDIATE
+   LEAVE-ORIG @ POSTPONE ONWARD-AHEAD LEAVE-ORIG ! ;
+: UNLOOP ( R: limit index -- ) IMMEDIATE
+   POSTPONE 2RDROP ;
+: +LOOP ( C: outer-stack dest -- S: n -- R: {limit index} -- ) IMMEDIATE
+   POSTPONE RSP@ POSTPONE +! POSTPONE 2R@ POSTPONE = POSTPONE UNTIL
+   LEAVE-ORIG @ POSTPONE THEN POSTPONE UNLOOP LEAVE-ORIG ! ;
+: LOOP ( C: outer-stack dest -- S: -- R: {limit index} -- ) IMMEDIATE
+   1 POSTPONE LITERAL POSTPONE +LOOP ;
+' LEAVE-ORIG (HIDE)
 
 \ Return the current index value from the innermost or next-innermost loop.
 \ The loops must be directly nested with no other changes to the return stack
 : I 1 RPICK ;
 : J 3 RPICK ;
 
+\ Remove trailing whitespace from a string (only affects length)
+: -TRAILING ( c-addr u1 -- c-addr u2 )
+   BEGIN DUP AND-THEN 2DUP 1- + C@ SPACE? THEN WHILE 1- REPEAT ;
+
+\ Return -1, 0, or 1 if the left string is respectively
+\ less than, equal to, or greater than the right string
+: COMPARE ( c-addr1 u1 c-addr2 u2 -- -1 | 0 | 1 )
+   ROT SWAP 2DUP - >R UMIN 0 ?DO
+      ( S: c-addr1 c-addr2 R: u1-u2 loop-sys )
+      OVER I + C@ OVER I + C@
+      ( S: c-addr1 c-addr2 ch1 ch2 )
+      - ?DUP IF NIP NIP SIGNUM UNLOOP RDROP EXIT THEN
+   LOOP
+   2DROP R> SIGNUM ;
+
 \ This function defines what happens when THROW is used outside of any CATCH
 : DEFAULT-UNWIND ( k*x n -- i*x <noreturn> )
    CASE
@@ -446,7 +503,7 @@ CREATE CURRENT-SOURCE-ID -1 ,
 : SAVE-INPUT ( -- xu ... x1 u ) >IN @ 1 ;
 : RESTORE-INPUT ( xu ... x1 u -- flag ) OVER >IN ! NDROP TRUE ;
 
-: PARSE-AREA ( -- c-addr u ) SOURCE >IN @ DROP-PREFIX ;
+: PARSE-AREA ( -- c-addr u ) SOURCE >IN @ /STRING ;
 
 : PARSE-EMPTY? ( -- flag ) SOURCE NIP >IN @ = ;
 
@@ -457,12 +514,66 @@ CREATE CURRENT-SOURCE-ID -1 ,
 
 : NEXT-CHAR ( -- c ) PEEK-CHAR SKIP-CHAR ;
 
-: SKIPSPACE ( "<spaces?>" -- )
+\ The size of this buffer will determine the maximum line length
+4096 CONSTANT TERMINAL-BUFFER-SIZE
+CREATE TERMINAL-BUFFER TERMINAL-BUFFER-SIZE ALLOT
+
+\ If we read more than one line then these will refer to the rest of the data
+CREATE TIB-LEFTOVER 0 ,
+CREATE TIB-LEFTOVER-SIZE 0 ,
+
+\ Attempt to replace the parse area with the next line from the current source
+\ Return TRUE if the parse area was refilled, or FALSE otherwise
+\ REFILL always fails if the current source is a string (from EVALUATE)
+: REFILL ( -- flag )
+   SOURCE-ID 0< IF FALSE EXIT THEN
+   \ Shift any leftover characters after the previous line to the start of the buffer
+   TIB-LEFTOVER @ TERMINAL-BUFFER TIB-LEFTOVER-SIZE @ CMOVE
+   \ Look for the linefeed character which marks the end of the first line
+   TIB-LEFTOVER-SIZE @ 0 BEGIN
+      \ If at the end with room in the buffer, read more from the file descriptor
+      2DUP = IF
+         DUP TERMINAL-BUFFER-SIZE U< IF
+            \ SOURCE-ID is the file descriptor number to read from
+            SOURCE-ID OVER DUP TERMINAL-BUFFER + SWAP TERMINAL-BUFFER-SIZE SWAP -
+            ( S: length idx src-id buff buff-size )
+            \ Repeat read if interrupted by a signal (returns -EINTR)
             BEGIN
-      PARSE-EMPTY? 0= AND-THEN PEEK-CHAR SPACE? THEN
+               SYS_READ SYSCALL3
-   WHILE
+               DUP ERRNO_EINTR NEGATE <>
-      SKIP-CHAR
+            UNTIL
-   REPEAT ;
+            \ Any other negative (error) return value is fatal
+            DUP 0< IF EXCP-FILE-IO THROW THEN
+            ( S: length idx u-read )
+            \ Add the amount of data read to the length; index is unchanged
+            ROT + SWAP
+         THEN
+      THEN
+      \ At this point if index equals length then buffer is full or read returned 0
+      \ Either way, we won't be reading any more into the buffer
+      2DUP = OR-ELSE
+         \ Check if the next character is a linefeed
+         1+ DUP 1- TERMINAL-BUFFER + C@ LF =
+      THEN
+   UNTIL
+   ( S: length idx )
+   \ idx is the next location after the linefeed, if found, or else equal to length
+   \ Save the rest, if any, for the next REFILL
+   DUP TERMINAL-BUFFER + TIB-LEFTOVER !
+   TUCK - TIB-LEFTOVER-SIZE !
+   ( S: idx )
+   \ The new input buffer is the first idx characters of the terminal buffer
+   TERMINAL-BUFFER INPUT-BUFFER !
+   DUP INPUT-BUFFER-SIZE !
+   DUP IF 0 >IN ! THEN
+   0<> ;
+
+' TIB-LEFTOVER (HIDE)
+' TIB-LEFTOVER-SIZE (HIDE)
+' TERMINAL-BUFFER (HIDE)
+
+: SKIP-SPACES ( "<spaces?>" -- )
+   BEGIN PARSE-EMPTY? OR-ELSE PEEK-CHAR SPACE? DUP IF SKIP-CHAR THEN 0= THEN UNTIL ;
 
 \ Comments; ignore all characters until the next EOL or ) character, respectively
 : \ ( "ccc<eol>" -- ) IMMEDIATE BEGIN NEXT-CHAR LF = UNTIL ;
@@ -471,10 +582,15 @@ CREATE CURRENT-SOURCE-ID -1 ,
 \ Skip whitespace; read and return the next word delimited by whitespace
 \ The delimiting whitespace character is left in the parse area
 : WORD ( "<spaces>ccc" -- c-addr u )
-   SKIPSPACE
+   BEGIN
+      SKIP-SPACES
+      PARSE-EMPTY?
+   WHILE
+      REFILL 0= IF 0 0 EXIT THEN
+   REPEAT
    PARSE-AREA DROP
    BEGIN
-      PARSE-EMPTY? OR-ELSE PEEK-CHAR SPACE? THEN 0=
+      PARSE-EMPTY? 0= AND-THEN PEEK-CHAR SPACE? 0= THEN
    WHILE
       SKIP-CHAR
    REPEAT
@@ -500,7 +616,7 @@ CREATE CURRENT-SOURCE-ID -1 ,
 
 ' (DOES) (HIDE)
 
-: (MARK) TYPE ": " TYPE .DS EOL ;
+: (MARK) "-- " TYPE TYPE " --\n" TYPE .S R> .RS >R ;
 : MARK IMMEDIATE WORD POSTPONE SLITERAL POSTPONE (MARK) ;
 ' (MARK) (HIDE)
 
@@ -555,7 +671,7 @@ CREATE CURRENT-SOURCE-ID -1 ,
    CREATE CELLS 2* ALLOT DOES> SWAP [ 2 CELLS ] LITERAL * + ;
 
 \ Define a threaded word which also displays its name and the data stack when called
-: (TRACE) >NAME TYPE SPACE .DS EOL ;
+: (TRACE) >NAME TYPE SPACE .S ;
 : :TRACE : LATEST POSTPONE LITERAL POSTPONE (TRACE) ;
 ' (TRACE) (HIDE)
 
@@ -587,7 +703,7 @@ CREATE CURRENT-SOURCE-ID -1 ,
 \ LATEST always refers to the innermost enclosing definition.
 \
 \ Example:
-\   > : TIMES 0 DO DUP EXECUTE LOOP DROP ;
+\   > : TIMES 0 ?DO DUP EXECUTE LOOP DROP ;
 \   > : GREETINGS { "Hello" TYPE EOL } 3 TIMES ;
 \   > GREETINGS
 \   Hello
@@ -630,6 +746,40 @@ CREATE CURRENT-SOURCE-ID -1 ,
       ( S: inner-xt )
    THEN ;
 
+\ Conditional compilation
+\ No effect if flag is true, otherwise skips words until matching [ELSE] or [THEN]
+\ Skips over nested [IF] … [THEN] or [IF] … [ELSE] … [THEN] structures
+: [IF] IMMEDIATE RECURSIVE
+   0= IF
+      0 BEGIN
+         WORD 2>R
+         2R@ "[IF]" COMPARE 0= IF
+            1+
+         ELSE 2R@ "[THEN]" COMPARE 0= OR-ELSE 2R@ "[ELSE]" COMPARE 0= THEN IF
+            ?DUP 0= IF 2RDROP EXIT THEN
+            1-
+         THEN THEN
+         2RDROP
+      AGAIN
+   THEN ;
+
+\ Skips words until matching [THEN]
+\ Skips over nested [IF] … [THEN] or [IF] … [ELSE] … [THEN] structures
+: [ELSE] IMMEDIATE
+   0 BEGIN
+      WORD 2>R
+      2R@ "[IF]" COMPARE 0= IF
+         1+
+      ELSE 2R@ "[THEN]" COMPARE 0= IF
+         ?DUP 0= IF 2RDROP EXIT THEN
+         1-
+      THEN THEN
+      2RDROP
+   AGAIN ;
+
+\ [THEN] is just a placeholder to terminate [IF] or [ELSE]; no compilation effect
+: [THEN] IMMEDIATE ;
+
 4096 CONSTANT PAGESIZE
 
 0 CONSTANT PROT_NONE
@@ -648,7 +798,7 @@ BUDDY-ORDERS 1- BUDDY-ORDER-BYTES CONSTANT BUDDY-MAX-BYTES
 BUDDY-ORDERS ARRAY BUDDY-HEADS
 
 : INIT-BUDDY-HEADS ( -- )
-   BUDDY-ORDERS 0 DO 0 I BUDDY-HEADS ! LOOP ;
+   BUDDY-ORDERS 0 ?DO 0 I BUDDY-HEADS ! LOOP ;
 
 INIT-BUDDY-HEADS
 
@@ -666,14 +816,14 @@ INIT-BUDDY-HEADS
       THEN
       ( S: order head-addr block-addr ) ( R: freed-addr )
       2 PICK 1+ BUDDY-ORDERS < AND-THEN
-         DUP 3 PICK BUDDY-ORDER-BYTES XOR R@ = AND-THEN
+         DUP 3 PICK BUDDY-ORDER-BYTES XOR R@ =
+      THEN AND-THEN
          \ Found the buddy on the free list; coalesce
          @ SWAP !
          \ Pick the lower (naturally aligned) block address
          DUP BUDDY-ORDER-BYTES INVERT R> AND >R
          \ Repeat process with the next-higher order
          1+ DUP BUDDY-HEADS TRUE
-         THEN
       THEN 0= IF
          \ Insert before first item with address >= this addr
          DUP R@ U>= IF R@ ! R> SWAP ! DROP EXIT THEN
@@ -723,7 +873,6 @@ VARIABLE TOTAL
 
 : ALLOCATE ( size -- a-addr )
    CELL+ DUP BUDDY-MAX-BYTES U> IF
-MARK A
       BEGIN
          NULL OVER PROT_READ PROT_WRITE OR
          MAP_PRIVATE MAP_ANONYMOUS OR -1 0 SYS_MMAP2 SYSCALL6
@@ -733,7 +882,6 @@ MARK A
       REPEAT
       TUCK ! CELL+ EXIT
    THEN
-MARK B
    NATURALLY-ALIGNED DUP BUDDY-MIN-BYTES U< IF DROP BUDDY-MIN-BYTES THEN
    BUDDY-ORDER-FROM-BYTES DUP BUDDY-ALLOCATE SWAP OVER ! CELL+ ;
 
@@ -753,34 +901,6 @@ MARK B
 : [CHAR] ( Compilation: "<spaces>ccc" -- ) ( Runtime: -- c ) IMMEDIATE
    CHAR POSTPONE LITERAL ;
 
-\ Return -1, 0, or 1 if the left string is respectively
-\ less than, equal to, or greater than the right string
-: COMPARE ( c-addr1 u1 c-addr2 u2 -- -1 | 0 | 1 )
-   BEGIN
-      ROT ?DUP IF
-         ( S: a1 a2 u2 u1 )
-         SWAP ?DUP IF
-            ( S: a1 a2 u1 u2 )
-            2SWAP 2DUP C@ SWAP C@ - DUP IF
-               >R 4 NDROP R> SIGNUM EXIT
-            ELSE
-               DROP
-               ( S: u1 u2 a1 a2 )
-               1+ SWAP 1+ 2SWAP 1- SWAP 1-
-               ( S: a2' a1' u2' u1' )
-               SWAP -ROT 2SWAP
-               ( S: a1' u1' a2' u2' )
-            THEN
-         ELSE
-            \ Return 1 since first string is longer
-            DROP 2DROP 1 EXIT
-         THEN
-      ELSE
-         \ If u2 is also zero return 0; else return -1 since first string is shorter
-         -ROT 2DROP 0<> EXIT
-      THEN
-   AGAIN ;
-
 \ Field accessors for the search order linked list
 : ORDER>LINK ( a-addr1 -- a-addr2 ) ;
 : ORDER>WID ( a-addr1 -- a-addr2 ) CELL+ ;
@@ -962,61 +1082,6 @@ VARIABLE ORDER-FREELIST
 : :REPLACE ( "<spaces>ccc" -- )
    : LATEST DUP >NAME FIND-OR-THROW DROP DUP (HIDE) DEFER! ;
 
-\ The size of this buffer will determine the maximum line length
-4096 CONSTANT TERMINAL-BUFFER-SIZE
-CREATE TERMINAL-BUFFER TERMINAL-BUFFER-SIZE ALLOT
-
-\ If we read more than one line then these will refer to the rest of the data
-CREATE TIB-LEFTOVER 0 ,
-CREATE TIB-LEFTOVER-SIZE 0 ,
-
-: REFILL ( -- flag )
-   SOURCE-ID 0< IF FALSE EXIT THEN
-   \ Shift any leftover characters after the previous line to the start of the buffer
-   TIB-LEFTOVER @ TERMINAL-BUFFER TIB-LEFTOVER-SIZE @ CMOVE
-   \ Look for the linefeed character which marks the end of the first line
-   TIB-LEFTOVER-SIZE @ 0 BEGIN
-      \ If at the end with room in the buffer, read more from the file descriptor
-      2DUP = IF
-         DUP TERMINAL-BUFFER-SIZE U< IF
-            \ SOURCE-ID is the file descriptor number to read from
-            SOURCE-ID OVER DUP TERMINAL-BUFFER + SWAP TERMINAL-BUFFER-SIZE SWAP -
-            ( S: length idx src-id buff buff-size )
-            \ Repeat read if interrupted by a signal (returns -EINTR)
-            BEGIN
-               SYS_READ SYSCALL3
-               DUP ERRNO_EINTR NEGATE <>
-            UNTIL
-            \ Any other negative (error) return value is fatal
-            DUP 0< IF EXCP-FILE-IO THROW THEN
-            ( S: length idx u-read )
-            \ Add the amount of data read to the length; index is unchanged
-            ROT + SWAP
-         THEN
-      THEN
-      \ At this point if index equals length then buffer is full or read returned 0
-      \ Either way, we won't be reading any more into the buffer
-      2DUP = OR-ELSE
-         \ Check if the next character is a linefeed
-         1+ DUP 1- TERMINAL-BUFFER + C@ LF =
-      THEN
-   UNTIL
-   ( S: length idx )
-   \ idx is the next location after the linefeed, if found, or else equal to length
-   \ Save the rest, if any, for the next REFILL
-   DUP TERMINAL-BUFFER + TIB-LEFTOVER !
-   TUCK - TIB-LEFTOVER-SIZE !
-   ( S: idx )
-   \ The new input buffer is the first idx characters of the terminal buffer
-   TERMINAL-BUFFER INPUT-BUFFER !
-   DUP INPUT-BUFFER-SIZE !
-   DUP IF 0 >IN ! THEN
-   0<> ;
-
-HIDE TIB-LEFTOVER
-HIDE TIB-LEFTOVER-SIZE
-HIDE TERMINAL-BUFFER
-
 : ESCAPED-CHAR ( "<escapeseq>" | "c" -- c )
    NEXT-CHAR DUP [CHAR] \ = IF
       DROP NEXT-CHAR CASE
@@ -1066,14 +1131,13 @@ HIDE TERMINAL-BUFFER
    REPEAT
    ( S: neg-flag accum c-addr' ) ( R: c-addr u )
    2RDROP DROP SWAP IF NEGATE THEN
-   TRUE
+   TRUE ;
-;
 
 \ Read a word, number, or string and either execute it or compile it
 \ The stack effect depends on the input and the current value of STATE
 : INTERPRET ( i*x "<spaces>ccc" -- j*x )
    BEGIN
-      SKIPSPACE
+      SKIP-SPACES
       PARSE-EMPTY? 0=
    WHILE
       PEEK-CHAR [CHAR] " = IF
@@ -1103,6 +1167,15 @@ HIDE TERMINAL-BUFFER
 DEFER SHOW-PROMPT
 { "> " TYPE } IS SHOW-PROMPT
 
+36 CONSTANT STRUCT-TERMIOS-BYTES
+21505 CONSTANT IOCTL_TCGETS
+CREATE TERMIOS STRUCT-TERMIOS-BYTES ALLOT ALIGN
+
+: TTY? ( fd -- flag )
+   IOCTL_TCGETS TERMIOS SYS_IOCTL SYSCALL3 0= ;
+
+STDIN TTY? CONSTANT INTERACTIVE?
+
 \ Redefine QUIT as a non-deferred word; update deferred references to point here
 \ Empty the return stack, make stdin the input source, and enter interpretation state
 :REPLACE QUIT ( -- <noreturn> )
@@ -1110,14 +1183,12 @@ DEFER SHOW-PROMPT
    0 CURRENT-SOURCE-ID !
    FALSE STATE !
    BEGIN
-      SHOW-PROMPT
+      [ INTERACTIVE? ] [IF] SHOW-PROMPT [THEN]
-      REFILL 0= IF
+      REFILL 0= IF BYE THEN
-         EOL BYE
-      THEN
       INTERPRET
-      STATE @ 0= IF
+      [ INTERACTIVE? ] [IF]
-         "OK\n" TYPE
+         STATE @ 0= IF "OK\n" TYPE THEN
-      THEN
+      [THEN]
    AGAIN ;
 
 : EVALUATE ( i*x c-addr u -- j*x )
@@ -1208,9 +1279,6 @@ DEFINITIONS
 \ From this point on we only execute threaded FORTH words defined in this file
 \ *****************************************************************************
 
-\ Return the number of words on the data stack
-: DEPTH ( -- n ) SP@ S0 SWAP - CELL / ;
-
 \ Return TRUE if the given address is the execution token of a word in
 \ the current search order or compilation word list, or FALSE otherwise
 \ The word's name may be hidden or shadowed by another definition
@@ -1259,7 +1327,7 @@ DEFINITIONS
 
 \ Display a string in escaped (double-quoted) format, without the delimiters
 : TYPE-ESCAPED ( c-addr u -- "<escapeseq*>" )
-   0 DO DUP 1+ SWAP C@ CASE
+   0 ?DO DUP 1+ SWAP C@ CASE
       0 OF "\\0" TYPE ENDOF
       7 OF "\\a" TYPE ENDOF
       8 OF "\\b" TYPE ENDOF
@@ -1362,7 +1430,10 @@ HIDE NONAME-LITERAL?
 
 HIDE UNTHREAD
 
+: WORDS ( -- )
+   GET-ORDER ?DUP IF 1- SWAP >R NDROP R> SHOW-WORDLIST THEN ;
+
 : BANNER "JumpForth version " TYPE VERSION . ", by Jesse McDonald\n" TYPE ;
 
-BANNER
+INTERACTIVE? [IF] BANNER [THEN]
 QUIT