basic.py - mozsearch

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# An implementation of Dartmouth BASIC (1964)

import sys

sys.path.insert(0, "../..")

if sys.version_info[0] >= 3:

    raw_input = input

import basiclex

import basparse

import basinterp

# If a filename has been specified, we try to run it.

# If a runtime error occurs, we bail out and enter

# interactive mode below

if len(sys.argv) == 2:

    data = open(sys.argv[1]).read()

    prog = basparse.parse(data)

    if not prog:

        raise SystemExit

    b = basinterp.BasicInterpreter(prog)

    try:

        b.run()

        raise SystemExit

    except RuntimeError:

        pass

else:

    b = basinterp.BasicInterpreter({})

# Interactive mode.  This incrementally adds/deletes statements

# from the program stored in the BasicInterpreter object.  In

# addition, special commands 'NEW','LIST',and 'RUN' are added.

# Specifying a line number with no code deletes that line from

# the program.

while 1:

    try:

        line = raw_input("[BASIC] ")

    except EOFError:

        raise SystemExit

    if not line:

        continue

    line += "\n"

    prog = basparse.parse(line)

    if not prog:

        continue

    keys = list(prog)

    if keys[0] > 0:

        b.add_statements(prog)

    else:

        stat = prog[keys[0]]

        if stat[0] == 'RUN':

            try:

                b.run()

            except RuntimeError:

                pass

        elif stat[0] == 'LIST':

            b.list()

        elif stat[0] == 'BLANK':

            b.del_line(stat[1])

        elif stat[0] == 'NEW':

            b.new()