Lichen

tests/getattr_visitor.py

934:2989aab1b4f7
7 months ago Paul Boddie Renamed the utf8string class to unicode, eliminating the unicode function. This means that the simple case of merely returning an object if it is already a Unicode object no longer occurs when using the unicode callable, but such behaviour might be better supported with more general customised instantiation functionality.
     1 class Expr:     2      3     "An expression."     4      5     def __init__(self, ops):     6         self.ops = ops     7      8     def children(self):     9         return self.ops    10     11 class Binary:    12     13     "A binary operator."    14     15     def __init__(self, left, op, right):    16         self.left = left    17         self.op = op    18         self.right = right    19     20     def children(self):    21         return self.left, self.right    22     23 class Unary:    24     25     "A unary operator."    26     27     def __init__(self, op, operand):    28         self.op = op    29         self.operand = operand    30     31     def children(self):    32         return self.operand,    33     34 class Value:    35     36     "A general value."    37     38     def __init__(self, value):    39         self.value = value    40     41     def children(self):    42         return ()    43     44 class Visitor:    45     46     "Visit nodes in an expression tree."    47     48     def __init__(self):    49         self.indent = 0    50     51     def visit(self, node):    52     53         # Obtain the method for the node name.    54     55         fn = getattr(self, node.__name__)    56     57         # Call the method.    58     59         fn(node)    60     61         # Visit the node's children.    62     63         self.visitChildren(node)    64     65     def visitChildren(self, node):    66         self.indent += 1    67         for n in node.children():    68             self.visit(n)    69         self.indent -= 1    70     71     def writeIndent(self):    72         i = 0    73         while i < self.indent:    74             print "",    75             i += 1    76     77     def Expr(self, node):    78         self.writeIndent()    79         print "Expression..."    80     81     def Binary(self, node):    82         self.writeIndent()    83         print "Binary operation", node.op    84     85     def Unary(self, node):    86         self.writeIndent()    87         print "Unary operation", node.op    88     89     def Value(self, node):    90         self.writeIndent()    91         print "Value", node.value    92     93 # Test the visitor with an example expression.    94     95 expr = Expr([Binary(Value(1), "+", Binary(Unary("-", Value(2)), "*", Value(3)))])    96 Visitor().visit(expr)