This is a simple stack machine that can carry out arbitrarily complex mathematical computations. It's not a universal machine as it lacks logical operators, conditional branching, and iteration, but the language it accepts can nevertheless approximate a wide range of functions.
A program for the machine is fed through the "run" method as a list of instructions and numbers. This serves as the input tape. Instructions are strings that are defined in the opcode tables below. These functions all take their arguments from the stack and return their results to the stack. Numbers can be integers or floats.
If the input tape's read-head encounters a number, it gets pushed onto the stack. If it comes across an instruction, it will check that there are an adequate number of arguments on the stack, pop them if there are, carry out the instruction, and push the result back on to the stack. Invalid items on the tape are ignored.
If there are no relevant arguments on the stack, the instruction gets skipped. The run method returns the number at the stop of the stack after the read-head comes to the end of the tape. Empty and invalid programs return 0.
stack = Marula()
stack.run([5, 5, "op_mul"]) #returns 25
stack.run([2, 80, "op_div"]) #80/2 returns 40.0
stack.run([5.7, "op_tanh"]) #returns 0.999978
stack.run([17, 8, "op_max"]) #returns 17