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# An implementation of Dartmouth BASIC (1964)
#
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:
with open(sys.argv[1]) as f:
data = f.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 True:
try:
line = 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()
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