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      1 # An implementation of Dartmouth BASIC (1964)
      2 #
      3 
      4 import sys
      5 sys.path.insert(0, "../..")
      6 
      7 if sys.version_info[0] >= 3:
      8     raw_input = input
      9 
     10 import basiclex
     11 import basparse
     12 import basinterp
     13 
     14 # If a filename has been specified, we try to run it.
     15 # If a runtime error occurs, we bail out and enter
     16 # interactive mode below
     17 if len(sys.argv) == 2:
     18     data = open(sys.argv[1]).read()
     19     prog = basparse.parse(data)
     20     if not prog:
     21         raise SystemExit
     22     b = basinterp.BasicInterpreter(prog)
     23     try:
     24         b.run()
     25         raise SystemExit
     26     except RuntimeError:
     27         pass
     28 
     29 else:
     30     b = basinterp.BasicInterpreter({})
     31 
     32 # Interactive mode.  This incrementally adds/deletes statements
     33 # from the program stored in the BasicInterpreter object.  In
     34 # addition, special commands 'NEW','LIST',and 'RUN' are added.
     35 # Specifying a line number with no code deletes that line from
     36 # the program.
     37 
     38 while 1:
     39     try:
     40         line = raw_input("[BASIC] ")
     41     except EOFError:
     42         raise SystemExit
     43     if not line:
     44         continue
     45     line += "\n"
     46     prog = basparse.parse(line)
     47     if not prog:
     48         continue
     49 
     50     keys = list(prog)
     51     if keys[0] > 0:
     52         b.add_statements(prog)
     53     else:
     54         stat = prog[keys[0]]
     55         if stat[0] == 'RUN':
     56             try:
     57                 b.run()
     58             except RuntimeError:
     59                 pass
     60         elif stat[0] == 'LIST':
     61             b.list()
     62         elif stat[0] == 'BLANK':
     63             b.del_line(stat[1])
     64         elif stat[0] == 'NEW':
     65             b.new()
     66