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Diffstat (limited to 'Lib/dos_8x3/ast.py')
| -rwxr-xr-x | Lib/dos_8x3/ast.py | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/Lib/dos_8x3/ast.py b/Lib/dos_8x3/ast.py new file mode 100755 index 0000000..6f92bee --- /dev/null +++ b/Lib/dos_8x3/ast.py @@ -0,0 +1,224 @@ +"""Object-oriented interface to the parser module. + +This module exports three classes which together provide an interface +to the parser module. Together, the three classes represent two ways +to create parsed representations of Python source and the two starting +data types (source text and tuple representations). Each class +provides interfaces which are identical other than the constructors. +The constructors are described in detail in the documentation for each +class and the remaining, shared portion of the interface is documented +below. Briefly, the three classes provided are: + +AST + Defines the primary interface to the AST objects and supports creation + from the tuple representation of the parse tree. + +ExpressionAST + Supports creation of expression constructs from source text. + +SuiteAST + Supports creation of statement suites from source text. + +FileSuiteAST + Convenience subclass of the `SuiteAST' class; loads source text of the + suite from an external file. + +Aside from the constructors, several methods are provided to allow +access to the various interpretations of the parse tree and to check +conditions of the construct represented by the parse tree. + +ast() + Returns the corresponding `parser.ASTType' object. + +code() + Returns the compiled code object. + +filename() + Returns the name of the associated source file, if known. + +isExpression() + Returns true value if parse tree represents an expression, or a false + value otherwise. + +isSuite() + Returns true value if parse tree represents a suite of statements, or + a false value otherwise. + +text() + Returns the source text, or None if not available. + +tuple() + Returns the tuple representing the parse tree. +""" + +__version__ = '$Revision$' +__copyright__ = """Copyright (c) 1995, 1996 by Fred L. Drake, Jr. + +This software may be used and distributed freely for any purpose provided +that this notice is included unchanged on any and all copies. The author +does not warrant or guarantee this software in any way. +""" + +class AST: + """Base class for Abstract Syntax Tree objects. + + Creates an Abstract Syntax Tree based on the tuple representation + of the parse tree. The parse tree can represent either an + expression or a suite; which will be recognized automatically. + This base class provides all of the query methods for subclass + objects defined in this module. + """ + _p = __import__('parser') # import internally to avoid + # namespace pollution at the + # top level + _text = None + _code = None + _ast = None + _type = 'unknown' + _tupl = None + + def __init__(self, tuple): + """Create an `AST' instance from a tuple-tree representation. + + tuple + The tuple tree to convert. + + The tuple-tree may represent either an expression or a suite; the + type will be determined automatically. + """ + if type(tuple) is not type(()): + raise TypeError, 'Base AST class requires tuple parameter.' + + self._tupl = tuple + self._ast = self._p.tuple2ast(tuple) + self._type = (self._p.isexpr(self._ast) and 'expression') or 'suite' + + def tuple(self): + """Returns the tuple representing the parse tree. + """ + if self._tupl is None: + self._tupl = self._p.ast2tuple(self._ast) + return self._tupl + + def code(self): + """Returns the compiled code object. + + The code object returned by this method may be passed to the + exec statement if `AST.isSuite()' is true or to the eval() + function if `AST.isExpression()' is true. All the usual rules + regarding execution of code objects apply. + """ + if not self._code: + self._code = self._p.compileast(self._ast) + return self._code + + def ast(self): + """Returns the corresponding `parser.ASTType' object. + """ + return self._ast + + def filename(self): + """Returns the name of the source file if known, or None. + """ + return None + + def text(self): + """Returns the source text, or None if not available. + + If the instance is of class `AST', None is returned since no + source text is available. If of class `ExpressionAST' or + `SuiteAST', the source text passed to the constructor is + returned. + """ + return self._text + + def isSuite(self): + """Determine if `AST' instance represents a suite of statements. + """ + return self._type == 'suite' + + def isExpression(self): + """Determine if `AST' instance represents an expression. + """ + return self._type == 'expression' + + + +class SuiteAST(AST): + """Statement suite parse tree representation. + + This subclass of the `AST' base class represents statement suites + parsed from the source text of a Python suite. If the source text + does not represent a parsable suite of statements, the appropriate + exception is raised by the parser. + """ + _type = 'suite' + + def __init__(self, text): + """Initialize a `SuiteAST' from source text. + + text + Source text to parse. + """ + if type(text) is not type(''): + raise TypeError, 'SuiteAST requires source text parameter.' + self._text = text + self._ast = self._p.suite(text) + + def isSuite(self): + return 1 + + def isExpression(self): + return 0 + + +class FileSuiteAST(SuiteAST): + """Representation of a python source file syntax tree. + + This provides a convenience wrapper around the `SuiteAST' class to + load the source text from an external file. + """ + def __init__(self, fileName): + """Initialize a `SuiteAST' from a source file. + + fileName + Name of the external source file. + """ + self._fileName = fileName + SuiteAST.__init__(self, open(fileName).read()) + + def filename(self): + return self._fileName + + + +class ExpressionAST(AST): + """Expression parse tree representation. + + This subclass of the `AST' base class represents expression + constructs parsed from the source text of a Python expression. If + the source text does not represent a parsable expression, the + appropriate exception is raised by the Python parser. + """ + _type = 'expression' + + def __init__(self, text): + """Initialize an expression AST from source text. + + text + Source text to parse. + """ + if type(text) is not type(''): + raise TypeError, 'ExpressionAST requires source text parameter.' + self._text = text + self._ast = self._p.expr(text) + + def isSuite(self): + return 0 + + def isExpression(self): + return 1 + + +# +# end of file |