Haichen Shen
117 lines
2.7 KiB
Python
117 lines
2.7 KiB
Python
"""Base class of symbolic expression"""
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from __future__ import absolute_import as _abs
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from numbers import Number as _Number
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from . import var_name as _name
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__addop__ = None
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__subop__ = None
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__mulop__ = None
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__divop__ = None
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class Expr(object):
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"""Base class of expression.
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Expression object should be in general immutable.
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"""
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def children(self):
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"""get children of this expression.
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Returns
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-------
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children : generator of children
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"""
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return ()
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def __add__(self, other):
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return BinaryOpExpr(__addop__, self, other)
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def __radd__(self, other):
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return self.__add__(other)
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def __sub__(self, other):
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return BinaryOpExpr(__subop__, self, other)
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def __rsub__(self, other):
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return BinaryOpExpr(__subop__, other, self)
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def __mul__(self, other):
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return BinaryOpExpr(__mulop__, self, other)
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def __rmul__(self, other):
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return BinaryOpExpr(__mulop__, other, self)
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def __div__(self, other):
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return BinaryOpExpr(__divop__, self, other)
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def __rdiv__(self, other):
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return BinaryOpExpr(__divop__, other, self)
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def __truediv__(self, other):
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return self.__div__(other)
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def __rtruediv__(self, other):
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return self.__rdiv__(other)
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def __neg__(self):
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return self.__mul__(-1)
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def _symbol(value):
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"""Convert a value to expression."""
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if isinstance(value, Expr):
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return value
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elif isinstance(value, _Number):
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return ConstExpr(value)
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else:
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raise TypeError("type %s not supported" % str(type(other)))
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class Var(Expr):
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"""Variable, is a symbolic placeholder.
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Each variable is uniquely identified by its address
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Note that name alone is not able to uniquely identify the var.
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Parameters
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----------
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name : str
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optional name to the var.
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"""
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def __init__(self, name=None):
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if name is None: name = 'i'
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self.name = _name.NameManager.current.get(name)
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class ConstExpr(Expr):
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"""Constant expression."""
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def __init__(self, value):
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assert isinstance(value, _Number)
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self.value = value
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class BinaryOpExpr(Expr):
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"""Binary operator expression."""
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def __init__(self, op, lhs, rhs):
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self.op = op
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self.lhs = _symbol(lhs)
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self.rhs = _symbol(rhs)
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def children(self):
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return (self.lhs, self.rhs)
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class UnaryOpExpr(Expr):
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"""Unary operator expression."""
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def __init__(self, op, src):
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self.op = op
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self.src = _symbol(src)
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def children(self):
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return (self.src)
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def const(value):
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"""Return a constant value"""
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return ConstExpr(value)
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