Source Code for Module osh.function

 1  # osh 
 2  # Copyright (C) 2005 Jack Orenstein <jao@geophile.com> 
 3  # 
 4  # This program is free software; you can redistribute it and/or modify 
 5  # it under the terms of the GNU General Public License as published by 
 6  # the Free Software Foundation; either version 2 of the License, or 
 7  # (at your option) any later version. 
 8  # 
 9  # This program is distributed in the hope that it will be useful, 
10  # but WITHOUT ANY WARRANTY; without even the implied warranty of 
11  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
12  # GNU General Public License for more details. 
13  # 
14  # You should have received a copy of the GNU General Public License 
15  # along with this program; if not, write to the Free Software 
16  # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
17   
18  """Encapsulates functions used in osh commands such as C{f} and C{select}. 
19   
20  osh function syntax:: 
21   
22      [[lambda] ARGS:] EXPRESSION 
23   
24  C{ARGS}: Comma-separated list of function arguments, optionally preceded by keyword 
25  C{lambda}. C{ARGS} may be omitted only for a function with no arguments. 
26   
27  C{EXPRESSION}: A Python expression written in terms of the function arguments. 
28   
29  Example:: 
30   
31      x: max(x, 10) 
32  """ 
33   
34  import copy 
35  import sys 
36  import types 
37   
38  import core 
39   
40  _LAMBDA = 'lambda ' 
41  _LAMBDA_COLON = 'lambda:' 
42   
43  # "Private" name (with leading underscore) so that epydoc doesn't document the class 
44 -class _Function(object): 
45      """Represents a function for use by osh commands with function arguments, 
46      e.g., select. 
47      """ 
48       
49      _function = None 
50      _function_id = None 
51   
52 -    def __init__(self, function_spec, namespace = core.__dict__): 
53          """Creates a Function. 
54          - function_spec: String specification of a function. Uses lambda notation, 
55            but the 'lambda' keyword is optional. 
56          - namespace: The default is reasonable; there's been no need to 
57            override it so far. 
58          """ 
59          if type(function_spec) in (types.FunctionType, types.BuiltinFunctionType): 
60              self._function = function_spec 
61          else: 
62              lambda_expression = self.parse(function_spec.strip()) 
63              # Create a namespace including symbols defined by the current osh invocation. 
64              namespace = copy.copy(namespace) 
65              namespace.update(core.namespace()) 
66              self._function = eval(lambda_expression, namespace) 
67   
68 -    def __call__(self, *args): # args = None): 
69          return self._function(*args) 
70   
71 -    def parse(self, function_spec): 
72          # If the function spec starts with a lambda, then just use it as is. 
73          # Otherwise, it could be: 
74          # - function with arg list, e.g. "x, y: x + y" 
75          # - zero-arg list with colon, e.g. ": processes()" 
76          # - zero-arg list without colon, e.g. "processes()" 
77          # Try prepending "lambda:" and "lambda" until there's 
78          # no syntax error. Crude but effective. 
79          if function_spec.startswith(_LAMBDA) or function_spec.startswith(_LAMBDA_COLON): 
80              # ok as is 
81              pass 
82          else: 
83              fixed_function_spec = '%s: %s' % (_LAMBDA, function_spec) 
84              try: 
85                  eval(fixed_function_spec) 
86                  function_spec = fixed_function_spec 
87              except: 
88                  fixed_function_spec = '%s %s' % (_LAMBDA, function_spec) 
89                  try: 
90                      eval(fixed_function_spec) 
91                      function_spec = fixed_function_spec 
92                  except: 
93                      raise Exception('Illegal function spec: %s' % function_spec) 
94          return function_spec 
95