Module grscheller.boring_math.cli.ackermann

# Copyright 2023-2024 Geoffrey R. Scheller
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Entry points for CLI scripts to evaluate Ackermann's function

The version of Ackermann's function being used is defined recursively by

```
   ackermann(0,n) = n+1
   ackermann(m,0) = ackermann(m-1,1)
   ackermann(m,n) = ackermann(m-1, ackermann(m, n-1)) for n,m > 0
```
Ackermann's function is an example of a computable but not primitively
recursive function.
"""

from __future__ import annotations

__all__ = ['ackermann_list_cli']
__author__ = "Geoffrey R. Scheller"
__copyright__ = "Copyright (c) 2023-2024 Geoffrey R. Scheller"
__license__ = "Apache License 2.0"

import sys
from grscheller.boring_math.recursive import ackermann_list

def ackermann_list_cli() -> None:
    """Evaluate Ackermann's function simulating the recursion with a Python list"""
    args = sys.argv[1:]
    if len(args) == 2:
        try:
            m = int(args[0])
            n = int(args[1])
            if m < 0 or n < 0:
                print("Error: Negative integer argument given" , file=sys.stderr)
                sys.exit(1)
        except ValueError:
            print("Error: Non-integer argument given", file=sys.stderr)
            sys.exit(1)
    else:
        print("Error: ackermann.py takes 2 arguments", file=sys.stderr)
        sys.exit(1)

    # Compute value
    print(ackermann_list(m, n))