+*-

+*- (say "add star minus") is an esolang very close to a Minsky machine, it is created by User:None1.

Commands

It had two unbounded accumulators named a and b, both set to zero at start of program.

Command	Meaning
+	Increment a
*	Swap a and b.
-	If a is 0, jump to the start of program, otherwise, decrement a.

Examples

Infinite loop

-

Computational class

This language is not Turing-complete: if both counters A and B are greater than the length of the program, the program reaches the end and halts. As such, it can be emulated using a finite-state machine plus one counter (the finite state remembers which of the counters is less than the length of the program and what its value is, and uses the counter to remember the value of the other counter); a finite-state machine plus one counter is not Turing-complete, and because it can emulate +*-, +*- must not be Turing-complete either. Proof by User:ais523.

See Also

• UBLANG
• Brainpocalypse

Implementations

Lua

s=io.read()a=0 b=0::e::for c in s:gmatch"."do if c==("-"):sub(a+1)then goto e end a,b=c=="+"and a+1 or(c=="*"and b or a-1),c=="*"and a or b end

Python interpreter with a debug command

c=input();p=a=b=0
while p<len(c):
 if c[p]=="+":a+=1
 elif c[p]=="*":a,b=b,a
 elif c[p]=="-":
  if a:a+=-1
  else:p=0
 elif c[p]=="d":print(a,b)
 p+=1