Esolang: AGAIN

AGAIN is a pathologically structured, multistack assembly language. The only memory the machines has is a collection of indexible stacks. Possibly circular haven't decided on that. The language has one syntatic blocks: IF ... END. The only means of jumping to a new location is AGAIN, which only jumps to the start of the program. The core language is defined by the following primitive instructions:

PUSH ( value index [index] -- [index]:value )

Pushes a value to the provided stack index.

POP ( index [index]:value -- value [index] )

Pops a value from the provided stack index.

PEEK ( index [index]:value -- value [index]:value )

Reads a value from the top of the provided stack index.

PEEKAT ( index o [index@o]:value -- value [index@o]:value)

Reads a value at some offset from the top of the provided stack index.

DROP ( value -- )

Drops a vaue from the main stack.

DUP ( value -- value value )

Duplicates value on main stack.

AGAIN ( -- )

Jumps to the top of the program.

ADD ( x y -- x+y )

Adds y to x

SUB ( x y -- x-y )

Subtracts y from x

MUL ( x y -- x*y )

Multiply x by y

DIV ( x y -- x/y )

Divides y by x

EQU ( x y -- x=y )

Takes two values on the main stack, returns if they are equal.

GTH ( x y -- x>y )

Takes two values on the main stack, returns if x > y

LTH ( x y -- x<y )

Takes two values on the main stack, returns if x < y

SHOW ( x -- )

Prints the number on the stack to the console

EMIT ( x -- )

Prints the number on the stack as its ASCII value to the console.

I don't really have any additional specs for this machine. Basically a rough sketch, don't even have an interpreter for it actually.

Example

This (probably) implements a factorial function. I don't have an interpreter so this is more an idea of it.

'main 1 PUSH
1 PEEK 'main EQUALS IF
    1 POP DROP 
    10 1 PUSH 'factorial 1 PUSH 'run 1 PUSH
END

1 PEEK DUP 'run EQUAL IF
    1 1 PEEKAT 'factorial IF
        1 POP DROP
        1 POP DROP 
        1 POP 2 PUSH
        'values 1 PUSH 'factorial
    END
END

1 PEEK 'factorial EQUAL IF
    1 1 PEEKAT 'values EQUAL IF
        2 PEEK 1 SUB 2 PUSH
        2 PEEK 1 > IF
            AGAIN
        END
        1 DROP 'product 1 PUSH
    END
    1 1 PEEKAT 'product EQUAL IF
        2 POP 2 POP DUP IF
            MUL 2 PUSH AGAIN
        END
    END
    1 POP DROP 
    1 POP DROP
END

2 POP SHOW