139 lines
3.9 KiB
Python
139 lines
3.9 KiB
Python
from keywords import Keyword
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"""
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The grammar is defined by the following constructs:
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The top level object is called GRAMMAR, which is the grammar for a class. It is a list object.
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Inside this list, each element can be any of the following:
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- a token (denoted by a Keyword enum)
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- a bitwise mask of the Keyword enum to denote multiple possibilities
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- Another list, to denote zero-or-more of a inner-sequence
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- A tuple, to denote zero-or-one of a inner-sequence
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- A lambda denotes a non-terminal part of the grammar
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This is basically an attempt to translate Figure 10.5 from the book into
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a Python structure.
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"""
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class Element:
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def __init__(self, name, grammar, terminal = False):
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self.name = name
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self.grammar = grammar
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self.terminal = terminal
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TYPES = Element('type', Keyword.INT | Keyword.CHAR | Keyword.BOOLEAN | Keyword.IDENTIFIER, True)
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CLASSVARDEC = Element('classVarDec', [
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# static|field type (, name)* ;
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Keyword.STATIC | Keyword.FIELD,
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TYPES,
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[Keyword.COMMA, Keyword.IDENTIFIER],
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Keyword.SEMICOLON
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])
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VARDEC = Element('varDec', [Keyword.VAR, TYPES, Keyword.IDENTIFIER,
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[Keyword.COMMA, Keyword.IDENTIFIER],
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Keyword.SEMICOLON
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])
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UNARY_OP = Element('unaryOp', Keyword.NOT | Keyword.MINUS, True)
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CONSTANT = Element('KeywordConstant', Keyword.TRUE | Keyword.FALSE|Keyword.NULL|Keyword.THIS, True)
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TERM = Element('term', Keyword.INTEGERCONSTANT | Keyword.STRINGCONSTANT | Keyword.TRUE | Keyword.FALSE | Keyword.IDENTIFIER)
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OP = Element('op', Keyword.PLUS | Keyword.MINUS | Keyword.MUL | Keyword.DIV | Keyword.AND | Keyword.OR | Keyword.GT | Keyword.LT | Keyword.EQ, True)
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EXPRESSION = Element('expression', [TERM, [OP, TERM]])
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EXPRESSIONLIST = Element('expressionList', (EXPRESSION, [Keyword.COMMA, EXPRESSION]))
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SUBROUTINE_CALL = Element('subroutineCall', {
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(Keyword.IDENTIFIER, Keyword.PARAN_OPEN): [
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EXPRESSIONLIST,
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Keyword.PARAN_CLOSE,
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],
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(Keyword.IDENTIFIER, Keyword.DOT): [
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Keyword.IDENTIFIER,
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Keyword.PARAN_OPEN,
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EXPRESSIONLIST,
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Keyword.PARAN_CLOSE
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]
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})
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STATEMENT = Element('statement', {
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(Keyword.LET): [Keyword.IDENTIFIER, (Keyword.SQUARE_OPEN, EXPRESSION, Keyword.SQUARE_CLOSE)],
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(Keyword.IF): [
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Keyword.PARAN_OPEN,
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EXPRESSION,
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Keyword.PARAN_CLOSE,
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Keyword.BRACE_OPEN,
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lambda: STATEMENTS,
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Keyword.BRACE_CLOSE,
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# This is the tricky one
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( Keyword.ELSE, Keyword.BRACE_OPEN, lambda:STATEMENT, Keyword.BRACE_CLOSE)
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],
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(Keyword.WHILE): [
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Keyword.PARAN_OPEN,
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EXPRESSION,
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Keyword.PARAN_CLOSE,
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Keyword.BRACE_OPEN,
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lambda: STATEMENTS,
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Keyword.BRACE_CLOSE,
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],
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(Keyword.DO): SUBROUTINE_CALL,
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(Keyword.RETURN): [(EXPRESSION), Keyword.SEMICOLON]
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})
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STATEMENTS = Element('statements', [STATEMENT])
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SUBROUTINE_BODY = Element('subroutineBody', [
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# One or more variable declarations
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# `var type varName (, varName)* ;`
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[VARDEC],
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STATEMENTS
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])
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""" Pseudo-element to help define subroutine declarations """
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RETURN_TYPES= Keyword.INT | Keyword.CHAR|Keyword.BOOLEAN|Keyword.IDENTIFIER|Keyword.VOID
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# Parameter List =
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# (
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# (type varName) (, type varName)*
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# )?
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# we use tuples for zero OR one of a sequence
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PARAMETER_LIST = Element('parameterList', (
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TYPES,
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Keyword.IDENTIFIER,
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[Keyword.COMMA, TYPES, Keyword.IDENTIFIER]
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))
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SUBROUTINEDEC = Element('subroutineDec', [
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# (constructor | function | method) (void | type) subRoutineName '(' parameterList ')'
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# subroutineBody
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Keyword.CONSTRUCTOR | Keyword.FUNCTION | Keyword.METHOD,
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RETURN_TYPES,
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Keyword.IDENTIFIER,
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Keyword.PARAN_OPEN,
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PARAMETER_LIST,
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Keyword.PARAN_CLOSE,
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# Subroutine Body {
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Keyword.BRACE_OPEN,
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SUBROUTINE_BODY,
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Keyword.BRACE_CLOSE,
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])
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CLASS = Element('class', [
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# class className {
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Keyword.CLASS,
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Keyword.IDENTIFIER,
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Keyword.BRACE_OPEN,
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# class Variable Declarations (one or more) = list
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CLASSVARDEC,
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# subroutine declarations (one or more) = list
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SUBROUTINEDEC,
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# }
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Keyword.BRACE_CLOSE
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])
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