June 2018 Update

Task/Execute-Brain----/ZX-Spectrum-Basic/execute-brain----.zx

@@ -0,0 +1,34 @@
+10 GO SUB 1000
+20 LET e=LEN p$
+30 LET a$=p$(ip)
+40 IF a$=">" THEN LET dp=dp+1
+50 IF a$="<" THEN LET dp=dp-1
+60 IF a$="+" THEN LET d(dp)=d(dp)+1
+70 IF a$="-" THEN LET d(dp)=d(dp)-1
+80 IF a$="." THEN PRINT CHR$ d(dp);
+90 IF a$="," THEN INPUT d(dp)
+100 IF a$="[" THEN GO SUB 500
+110 IF a$="]" THEN LET bp=bp-1: IF d(dp)<>0 THEN LET ip=b(bp)-1
+120 LET ip=ip+1
+130 IF ip>e THEN PRINT "eof": STOP
+140 GO TO 30
+
+499 REM match close
+500 LET bc=1: REM bracket counter
+510 FOR x=ip+1 TO e
+520 IF p$(x)="[" THEN LET bc=bc+1
+530 IF p$(x)="]" THEN LET bc=bc-1
+540 IF bc=0 THEN LET b(bp)=ip: LET be=x: LET x=e: REM bc will be 0 once all the subnests have been counted over
+550 IF bc=0 AND d(dp)=0 THEN LET ip=be: LET bp=bp-1
+560 NEXT x
+570 LET bp=bp+1
+580 RETURN
+
+999 REM initialisation
+1000 DIM d(100): REM data stack
+1010 LET dp=1: REM data pointer
+1020 LET ip=1: REM instruction pointer
+1030 DIM b(30): REM bracket stack
+1040 LET bp=1: REM bracket pointer
+1050 LET p$="++++++++[>++++[>++>+++>+++>+<<<<-]>+>+>->>+[<]<-]>>.>---.+++++++..+++.>>.<-.<.+++.------.--------.>>+.>+++++.": REM program, marginally modified from Wikipedia; outputs CHR$ 13 at the end instead of CHR$ 10 as ZX Spectrum Basic handles the carriage return better than the line feed
+1060 RETURN