ext/ply/example/BASIC/basic.py

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