: / /MOD SWAP DROP ;
: MOD /MOD DROP ;
-: */ * / ;
+: */ -ROT * SWAP / ;
: NEGATE 0 SWAP - ;
, \ compile it
;
+: DEBUGON TRUE DEBUG ! ;
+: DEBUGOFF FALSE DEBUG ! ;
+
\ CONTROL STRUCTURES ----------------------------------------------------------------------
: IF IMMEDIATE
;
: DO IMMEDIATE
+ ' LIT , -1 , [COMPILE] IF
' >R , ' >R ,
+ ' LIT , HERE @ 0 , ' >R ,
HERE @
;
-: I RSP@ 2- @ ;
+: ?DO IMMEDIATE
+ ' 2DUP , ' - , [COMPILE] IF
+ ' >R , ' >R ,
+ ' LIT , HERE @ 0 , ' >R ,
+ HERE @
+;
-: LOOP+ IMMEDIATE
- ' R> , ' R> , ' -ROT , ' + , ' 2DUP , ' - ,
- ' SWAP , ' >R , ' SWAP , ' >R ,
- ' 0<= , ' 0BRANCH ,
- HERE @ - ,
- ' RDROP , ' RDROP ,
+: I RSP@ 3 - @ ;
+
+: J RSP@ 6 - @ ;
+
+: ?LEAVE IMMEDIATE
+ ' 0BRANCH , 13 ,
+ ' R> , ' RDROP , ' RDROP ,
+ ' LIT , HERE @ 7 + , ' DUP , ' -ROT , ' - , ' SWAP , ' ! ,
+ ' BRANCH ,
+ 0 ,
;
-: LOOP IMMEDIATE
- ' LIT , 1 ,
- [COMPILE] LOOP+
+: LEAVE IMMEDIATE
+ ' LIT , -1 ,
+ [COMPILE] ?LEAVE
+;
+
+: +LOOP IMMEDIATE
+ ' DUP , \ Store copy of increment
+
+ ' R> , ' SWAP , ' R> , ' SWAP , ' R> , ' SWAP , ' + , ' 2DUP , ' - ,
+ ' SWAP , ' >R , ' SWAP , ' >R , ' SWAP , ' >R ,
+
+ \ Condition differently depending on sign of increment
+ ' SWAP , ' 0>= , [COMPILE] IF
+ ' 0<= ,
+ [COMPILE] ELSE
+ ' 0> ,
+ [COMPILE] THEN
+
+ \ Branch back to begining of loop kernel
+ ' 0BRANCH , HERE @ - ,
+
+ \ Clean up
+ ' RDROP , ' RDROP , ' RDROP ,
+
+ \ Record address of loop end for any LEAVEs to use
+ HERE @ SWAP !
+
+ [COMPILE] ELSE
+ ' 2DROP , \ Clean up if loop was entirely skipped (?DO)
+ [COMPILE] THEN
;
+: LOOP IMMEDIATE
+ ' LIT , 1 ,
+ [COMPILE] +LOOP
+;
\ COMMENTS ----------------------------------------------------------------------
( Some more complicated stack examples, showing the stack notation. )
: NIP ( x y -- y ) SWAP DROP ;
-: TUCK ( x y -- y x y ) DUP ROT ;
+: TUCK ( x y -- y x y ) DUP -ROT ;
: PICK ( x_u ... x_1 x_0 u -- x_u ... x_1 x_0 x_u )
1+ ( add one because of 'u' on the stack )
PSP@ SWAP - ( add to the stack pointer )
@ ( and fetch )
;
-
+: ROLL ( x_u x_u-1... x_0 u -- x_u-1 ... x_0 x_u )
+ 1+ DUP PICK SWAP ( x_u x_u-1 ... x_0 x_u u+1 )
+ PSP@ 1- SWAP - PSP@ 2- SWAP
+ DO
+ i 1+ @ i !
+ LOOP
+ SWAP DROP
+;
( With the looping constructs, we can now write SPACES, which writes n spaces to stdout. )
: SPACES ( n -- )
- BEGIN
- DUP 0> ( while n > 0 )
- WHILE
- SPACE ( print a space )
- 1- ( until we count down to 0 )
- REPEAT
- DROP
+ DUP 0> IF
+ 0 DO SPACE LOOP
+ ELSE
+ DROP
+ THEN
;
( Standard words for manipulating BASE. )
SWAP ( width u )
DUP ( width u u )
UWIDTH ( width u uwidth )
- -ROT ( u uwidth width )
+ ROT ( u uwidth width )
SWAP - ( u width-uwidth )
( At this point if the requested width is narrower, we'll have a negative number on the stack.
Otherwise the number on the stack is the number of spaces to print. But SPACES won't print
DUP 0< IF
NEGATE ( width u )
1 ( save a flag to remember that it was negative | width n 1 )
- ROT ( 1 width u )
+ -ROT ( 1 width u )
SWAP ( 1 u width )
1- ( 1 u width-1 )
ELSE
0 ( width u 0 )
- ROT ( 0 width u )
+ -ROT ( 0 width u )
SWAP ( 0 u width )
THEN
SWAP ( flag width u )
DUP ( flag width u u )
UWIDTH ( flag width u uwidth )
- -ROT ( flag u uwidth width )
+ ROT ( flag u uwidth width )
SWAP - ( flag u width-uwidth )
SPACES ( flag u )
( c a b WITHIN returns true if a <= c and c < b )
: WITHIN
- ROT ( b c a )
+ -ROT ( b c a )
OVER ( b c a c )
<= IF
> IF ( b c -- )
FALSE
THEN
;
-