135 lines
5.1 KiB
Python
135 lines
5.1 KiB
Python
#! /usr/bin/python
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# SPDX-License-Identifier: GPL-3.0-or-later
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <https://www.gnu.org/licenses/>.
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"""This class implements a BASIC interpreter that
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presents a prompt to the user. The user may input
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program statements, list them and run the program.
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The program may also be saved to disk and loaded
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again.
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"""
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from basictoken import BASICToken as Token
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from lexer import Lexer
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from program import Program
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from sys import stderr
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from traceback import print_exception
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def main():
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banner = (r"""
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._____________ ___________. ___ ___________ ______
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| _ .__ \ / ___ _ \ / \ / | / |
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| |_) | \ \/ / | |_) | / ^ \ | (----`| | | ,----'
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| ___/ \_ _/ | _ < / /_\ \ \ \ | | | |
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| | | | | |_) \/ _____ \----) | | | | `----.
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| _| |__| |___________/ \_________/ |____________|
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""")
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print(banner)
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lexer = Lexer()
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program = Program()
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# Continuously accept user input and act on it until
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# the user enters 'EXIT'
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while True:
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stmt = input('> ')
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try:
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tokenlist = lexer.tokenize(stmt)
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# Execute commands directly, otherwise
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# add program statements to the stored
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# BASIC program
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if len(tokenlist) > 0:
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# Exit the interpreter
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if tokenlist[0].category == Token.EXIT:
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break
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# Add a new program statement, beginning
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# a line number
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elif tokenlist[0].category == Token.UNSIGNEDINT\
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and len(tokenlist) > 1:
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program.add_stmt(tokenlist)
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# Delete a statement from the program
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elif tokenlist[0].category == Token.UNSIGNEDINT \
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and len(tokenlist) == 1:
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program.delete_statement(int(tokenlist[0].lexeme))
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# Execute the program
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elif tokenlist[0].category == Token.RUN:
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try:
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program.execute()
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except KeyboardInterrupt:
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print("Program terminated")
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# List the program
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elif tokenlist[0].category == Token.LIST:
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if len(tokenlist) == 2:
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program.list(int(tokenlist[1].lexeme),int(tokenlist[1].lexeme))
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elif len(tokenlist) == 3:
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# if we have 3 tokens, it might be LIST x y for a range
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# or LIST -y or list x- for a start to y, or x to end
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if tokenlist[1].lexeme == "-":
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program.list(None, int(tokenlist[2].lexeme))
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elif tokenlist[2].lexeme == "-":
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program.list(int(tokenlist[1].lexeme), None)
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else:
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program.list(int(tokenlist[1].lexeme),int(tokenlist[2].lexeme))
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elif len(tokenlist) == 4:
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# if we have 4, assume LIST x-y or some other
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# delimiter for a range
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program.list(int(tokenlist[1].lexeme),int(tokenlist[3].lexeme))
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else:
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program.list()
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# Save the program to disk
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elif tokenlist[0].category == Token.SAVE:
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program.save(tokenlist[1].lexeme)
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print("Program written to file")
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# Load the program from disk
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elif tokenlist[0].category == Token.LOAD:
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program.load(tokenlist[1].lexeme)
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print("Program read from file")
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# Delete the program from memory
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elif tokenlist[0].category == Token.NEW:
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program.delete()
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# Unrecognised input
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else:
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print("Unrecognised input", file=stderr)
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for token in tokenlist:
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token.print_lexeme()
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print(flush=True)
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# Trap all exceptions so that interpreter
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# keeps running
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except Exception as e:
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print_exception(e,e, \
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e.__traceback__ if hasattr(e,'__traceback__') else None)
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if __name__ == "__main__":
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main()
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