In Vorth, most things are done to conserve space. Here is some working code like that which the Vorth metacompiler will generate. This one makes a little bird fly around on the VIC-20 display. The whole thing, including a BASIC bootstrap and the Vorth inner interpreter with a few primitives, takes up less than 300 bytes of RAM.
Only words that are required by the outermost definition ("the app") are compiled into the target dictionary. First, this little bit of BASIC bootstrap to call Vorth at $100D :
Code:
6502 sys4109
(C:$11f0) m 1000 100f
>C:1000 00 0b 10 66 19 9e 34 31 30 39 00 00 00 a9 00 85 ...f..4109......
(C:$114f) d 100d
.C:100d .basend:
.C:100d A9 00 LDA #$00
.C:100f 85 04 STA $04 ; shadow IP, put a zero here...
.C:1011 A9 FF LDA #$FF
.C:1013 8D 0F 90 STA $900F ; yellow/light yellow border/background
.C:1016 A9 52 LDA #$52
.C:1018 8D 16 03 STA .BRKVEC
.C:101b A9 10 LDA #$10 ; `brk` instruction performs `enter`
.C:101d 8D 17 03 STA $0317 ; the rest of `enter` is at $1052
.C:1020 .restart:
.C:1020 6C 93 11 JMP (.userstartup) ; on to the main event!
.C:1023 .delay:
.C:1023 20 F5 10 JSR .docreate ; variable delay 5 delay !
.C:1026 05
.C:1027 .exit:
.C:1027 68 PLA
.C:1028 A8 TAY ; IP low byte
.C:1029 68 PLA
.C:102a 68 PLA
.C:102b 68 PLA
.C:102c 68 PLA ; `enter` left 6 bytes, discard most of it
.C:102d 68 PLA ; IP high byte
.C:102e .gotoay:
.C:102e 8D 3A 10 STA .iphi
.C:1031 D0 02 BNE .nextx ; bra
.C:1033 .spstore:
.C:1033 A2 00 LDX #$00
.C:1035 .nextx:
.C:1035 86 60 STX .STACK
.C:1037 .next:
.C:1037 C8 INY ;[2]
.C:1038 .nexto:
.C:1038 BE 00 11 LDX $1100,Y ;[4]
.C:103b BD B8 11 LDA .cfahi,X ;[4]
.C:103e 48 PHA ;[3]
(C:$103f) d
.C:103f BD 95 11 LDA .cfalo,X ;[4]
.C:1042 48 PHA ;[3]
.C:1043 A6 60 LDX .STACK ;[3]
.C:1045 60 RTS ;[6 = 29 total clocks]
.C:1046 .bumpip:
.C:1046 C8 INY
.C:1047 D0 03 BNE .bumpip01
.C:1049 EE 3A 10 INC .iphi
.C:104c .bumpip01:
.C:104c AD 3A 10 LDA .iphi
.C:104f 85 05 STA $05 ; shadow IP at ($04)
.C:1051 60 RTS
;brk
;($FFFE) --> $FF72
;FF72:
;pha ; VIC-20 ROM stuff
;txa
;pha
;tya
;pha
;tsx
;lda $0104,x
;and #$10
;bne $FF82
;jmp (.BRKVEC) --> $1052 BRK vector
;FF82:
;jmp ($0314) ; hardware IRQ
.C:1052 .enter:
.C:1052 58 CLI
.C:1053 BC 06 01 LDY $0106,X
.C:1056 AD 3A 10 LDA .iphi
.C:1059 9D 06 01 STA $0106,X
.C:105c 8C 3A 10 STY .iphi
.C:105f BC 05 01 LDY $0105,X
.C:1062 88 DEY
.C:1063 4C 38 10 JMP .nexto
.C:1066 .qbranch:
.C:1066 20 46 10 JSR .bumpip
.C:1069 E8 INX
.C:106a B5 60 LDA .STACK,X
.C:106c D0 06 BNE .branch01
.C:106e 4C 35 10 JMP .nextx
.C:1071 .branch:
.C:1071 20 46 10 JSR .bumpip
.C:1074 .branch01:
.C:1074 98 TYA
.C:1075 18 CLC
.C:1076 71 04 ADC ($04),Y
.C:1078 A8 TAY
.C:1079 4C 35 10 JMP .nextx
.C:107c .cfetch:
.C:107c A1 60 LDA (.STACK,X)
.C:107e 95 61 STA $61,X
.C:1080 4C 88 10 JMP .drop
.C:1083 .emit:
.C:1083 B5 60 LDA .STACK,X
.C:1085 20 D2 FF JSR $FFD2
.C:1088 .drop:
.C:1088 E8 INX
.C:1089 4C 35 10 JMP .nextx
.C:108c .three:
.C:108c A9 03 LDA #$03
.C:108e 2C A9 20 BIT $20A9 ; bl:
.C:1091 2C B5 62 BIT $62B5 ; third:
.C:1094 2C B5 61 BIT $61B5 ; over:
.C:1097 2C B5 60 BIT $60B5 ; dup:
.C:109a CA DEX
.C:109b 95 60 STA .STACK,X
.C:109d 4C 35 10 JMP .nextx
.C:10a0 .swap:
.C:10a0 B5 60 LDA .STACK,X
.C:10a2 48 PHA
.C:10a3 B5 61 LDA $61,X
.C:10a5 95 60 STA .STACK,X
.C:10a7 68 PLA
.C:10a8 95 61 STA $61,X
.C:10aa 4C 37 10 JMP .next
.C:10ad .rot:
.C:10ad B5 60 LDA .STACK,X
.C:10af 48 PHA
.C:10b0 B5 61 LDA $61,X
.C:10b2 48 PHA
.C:10b3 B5 62 LDA $62,X
.C:10b5 95 60 STA .STACK,X
.C:10b7 68 PLA
.C:10b8 95 62 STA $62,X
.C:10ba 68 PLA
.C:10bb 95 61 STA $61,X
.C:10bd 4C 37 10 JMP .next
.C:10c0 .minus:
.C:10c0 B5 61 LDA $61,X
.C:10c2 49 FF EOR #$FF
.C:10c4 95 61 STA $61,X
.C:10c6 38 SEC
.C:10c7 29 18 AND #$18 ; mplus:
.C:10c9 B5 60 LDA .STACK,X
.C:10cb 75 61 ADC $61,X
.C:10cd 90 02 BCC .mplus01
.C:10cf F6 62 INC $62,X
.C:10d1 .mplus01:
.C:10d1 95 61 STA $61,X
.C:10d3 E8 INX
.C:10d4 4C 35 10 JMP .nextx
.C:10d7 .or:
.C:10d7 B5 60 LDA .STACK,X
.C:10d9 15 61 ORA $61,X
.C:10db 4C D1 10 JMP .mplus01
.C:10de .andx:
.C:10de B5 60 LDA .STACK,X
.C:10e0 35 61 AND $61,X
.C:10e2 4C D1 10 JMP .mplus01
.C:10e5 .xor:
.C:10e5 B5 60 LDA .STACK,X
.C:10e7 55 61 EOR $61,X
.C:10e9 4C D1 10 JMP .mplus01
.C:10ec .oneplus:
.C:10ec F6 60 INC .STACK,X
.C:10ee D0 02 BNE .oneplus01
.C:10f0 F6 61 INC $61,X
.C:10f2 .oneplus01:
.C:10f2 4C 37 10 JMP .next
.C:10f5 .docreate:
.C:10f5 CA DEX
.C:10f6 CA DEX
.C:10f7 68 PLA
.C:10f8 95 60 STA .STACK,X
.C:10fa 68 PLA
.C:10fb 95 61 STA $61,X
.C:10fd 86 60 STX .STACK
.C:10ff 4C EC 10 JMP .oneplus
.C:1102 .randu:
.C:1102 38 SEC ; from Butterfield's "First Book of KIM-1"
.C:1103 AD 23 11 LDA $1123
.C:1106 6D 26 11 ADC $1126
.C:1109 6D 27 11 ADC $1127
.C:110c 8D 22 11 STA .random
.C:110f A2 04 LDX #$04
.C:1111 .ripl:
.C:1111 BD 22 11 LDA .random,X
.C:1114 9D 23 11 STA $1123,X
.C:1117 CA DEX
.C:1118 10 F7 BPL .ripl
.C:111a A6 60 LDX .STACK
.C:111c CA DEX
.C:111d 95 60 STA .STACK,X
.C:111f 4C 35 10 JMP .nextx
.C:1122 .random:
.C:1122 9C 9C D8 SHY $D89C,X
.C:1125 D8 CLD
.C:1126 9D E7 20 STA $20E7,X
.C:1129 E1 FF SBC ($FF,X)
.C:112b D0 02 BNE .pushz
.C:112d .notz:
.C:112d 18 CLC
.C:112e 29 38 AND #$38
.C:1130 A9 00 LDA #$00
.C:1132 E9 00 SBC #$00
.C:1134 CA DEX
.C:1135 95 60 STA .STACK,X
.C:1137 4C 35 10 JMP .nextx
.C:113a .threedot:
.C:113a A2 03 LDX #$03 ; emit 3 bytes, coded inline
.C:113c .threedot01:
.C:113c 20 46 10 JSR .bumpip
.C:113f B1 04 LDA ($04),Y
.C:1141 20 D2 FF JSR $FFD2
.C:1144 CA DEX
.C:1145 D0 F5 BNE .threedot01
.C:1147 4C 37 10 JMP .next
.C:114a .jiffies:
.C:114a B5 60 LDA .STACK,X
.C:114c 18 CLC
.C:114d 65 A2 ADC $A2
.C:114f .jiffies01:
.C:114f C5 A2 CMP $A2
.C:1151 D0 FC BNE .jiffies01
.C:1153 4C 88 10 JMP .drop
.C:1156 .compass:
.C:1156 20 F5 10 JSR .docreate
.C:1159 1D 9D 11 ORA $119D,X ; [rt] [lf] [dn] [up]
.C:115c 91 00 STA ($00),Y ; : 3<- ( -- ) 3. [lf] [lf] [lf] ;
.C:115e 1A NOOP
.C:115f 9D 9D 9D STA $9D9D,X
.C:1162 ._zz:
.C:1162 00 BRK ; : zz ( -- ) delay @ jiffies ;
.C:1163 01 07 ORA ($07,X)
.C:1165 1B 00 1A SLO $1A00,Y ; : flap ( -- ) 3.
.C:1168 D5 D7 CMP $D7,X ; [U] [W] [I]
.C:116a C9 1C CMP #$1C ; 3<-
.C:116c 1D 1A C0 ORA $C01A,X ; zz 3. [@] [W] [@]
.C:116f D7 C0 DCP $C0,X
.C:1171 1C 1D 1A NOOP $1A1D,X ; 3<- zz 3.
.C:1174 CA DEX
.C:1175 D7 CB DCP $CB,X ; [J] [W] [K]
.C:1177 1C 1D 1A NOOP $1A1D,X ; 3<- zz 3.
(C:$117a) m 1150
>C:1150 a2 d0 fc 4c 88 10 20 f5 10 1d 9d 11 91 00 1a 9d ...L.. .........
>C:1160 9d 9d 00 01 07 1b 00 1a d5 d7 c9 1c 1d 1a c0 d7 ................
>C:1170 c0 1c 1d 1a ca d7 cb 1c 1d 1a c0 d7 c0 1c 1d 1a ................
; [@] [W] [@] 3<- zz 3.
>C:1180 20 20 20 1c 00 1f 16 0a 14 12 07 08 00 1e 1e 20 ............
; [sp] [sp] [sp] 3<- ;
; : flit ( -- ) compass randu
; 3 and m+ c@ emit ;
;118C:
; : fly ( -- )
; begin
; flap flap flit
>C:1190 17 05 fa 8c 11 26 22 32 36 51 65 70 7b 82 87 8b .....&"26Qep{...
; ?terminal
; until ;
; (startup) --> $118C
;
; [35 tokens]
; CFA low bytes
; CFA high bytes
>C:11a0 8e 91 94 97 9f ac bf c7 d6 dd e4 01 27 2c 2e 39 ............',.9
>C:11b0 49 5c 61 65 55 83 8b 92 10 10 10 10 10 10 10 10 I\aeU...........
>C:11c0 10 10 10 10 10 10 10 10 10 10 10 10 10 10 11 11 ................
>C:11d0 11 11 11 11 11 11 11 11 11 11 11 ff ff ff ff ff ................
>C:11e0 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
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