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# This file is part of daf_butler. 

# 

# Developed for the LSST Data Management System. 

# This product includes software developed by the LSST Project 

# (https://www.lsst.org). 

# See the COPYRIGHT file at the top-level directory of this distribution 

# for details of code ownership. 

# 

# This program is free software: you can redistribute it and/or modify 

# it under the terms of the GNU General Public License as published by 

# the Free Software Foundation, either version 3 of the License, or 

# (at your option) any later version. 

# 

# This program is distributed in the hope that it will be useful, 

# but WITHOUT ANY WARRANTY; without even the implied warranty of 

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU General Public License for more details. 

# 

# You should have received a copy of the GNU General Public License 

# along with this program. If not, see <https://www.gnu.org/licenses/>. 

 

"""Module which defines classes for intermediate representation of the 

expression tree produced by parser. 

 

The purpose of the intermediate representation is to be able to generate 

same expression as a part of SQL statement with the minimal changes. We 

will need to be able to replace identifiers in original expression with 

database-specific identifiers but everything else will probably be sent 

to database directly. 

""" 

 

__all__ = ['Node', 'BinaryOp', 'Identifier', 'IsIn', 'NumericLiteral', 

'Parens', 'StringLiteral', 'UnaryOp'] 

 

# ------------------------------- 

# Imports of standard modules -- 

# ------------------------------- 

from abc import ABC, abstractmethod 

 

# ----------------------------- 

# Imports for other modules -- 

# ----------------------------- 

 

# ---------------------------------- 

# Local non-exported definitions -- 

# ---------------------------------- 

 

# ------------------------ 

# Exported definitions -- 

# ------------------------ 

 

 

class Node(ABC): 

"""Base class of IR node in expression tree. 

 

The purpose of this class is to simplify visiting of the 

all nodes in a tree. It has a list of sub-nodes of this 

node so that visiting code can navigate whole tree without 

knowing exct types of each node. 

 

Attributes 

---------- 

children : tuple of :py:class:`Node` 

Possibly empty list of sub-nodes. 

""" 

def __init__(self, children=None): 

self.children = tuple(children or ()) 

 

@abstractmethod 

def visit(self, visitor): 

"""Implement Visitor pattern for parsed tree. 

 

Parameters 

---------- 

visitor : `TreeVisitor` 

Instance of vistor type. 

""" 

 

 

class BinaryOp(Node): 

"""Node representing binary operator. 

 

This class is used for representing all binary operators including 

arithmetic and boolean operations. 

 

Attributes 

---------- 

lhs : Node 

Left-hand side of the operation 

rhs : Node 

Right-hand side of the operation 

op : str 

Operator name, e.g. '+', 'OR' 

""" 

def __init__(self, lhs, op, rhs): 

Node.__init__(self, (lhs, rhs)) 

self.lhs = lhs 

self.op = op 

self.rhs = rhs 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

lhs = self.lhs.visit(visitor) 

rhs = self.rhs.visit(visitor) 

return visitor.visitBinaryOp(self.op, lhs, rhs, self) 

 

def __str__(self): 

return "{lhs} {op} {rhs}".format(**vars(self)) 

 

 

class UnaryOp(Node): 

"""Node representing unary operator. 

 

This class is used for representing all unary operators including 

arithmetic and boolean operations. 

 

Attributes 

---------- 

op : str 

Operator name, e.g. '+', 'NOT' 

operand : Node 

Operand. 

""" 

def __init__(self, op, operand): 

Node.__init__(self, (operand,)) 

self.op = op 

self.operand = operand 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

operand = self.operand.visit(visitor) 

return visitor.visitUnaryOp(self.op, operand, self) 

 

def __str__(self): 

return "{op} {operand}".format(**vars(self)) 

 

 

class StringLiteral(Node): 

"""Node representing string literal. 

 

Attributes 

---------- 

value : str 

Literal value. 

""" 

def __init__(self, value): 

Node.__init__(self) 

self.value = value 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

return visitor.visitStringLiteral(self.value, self) 

 

def __str__(self): 

return "'{value}'".format(**vars(self)) 

 

 

class NumericLiteral(Node): 

"""Node representing string literal. 

 

We do not convert literals to numbers, their text representation 

is stored literally. 

 

Attributes 

---------- 

value : str 

Literal value. 

""" 

def __init__(self, value): 

Node.__init__(self) 

self.value = value 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

return visitor.visitNumericLiteral(self.value, self) 

 

def __str__(self): 

return "{value}".format(**vars(self)) 

 

 

class Identifier(Node): 

"""Node representing identifier. 

 

Value of the identifier is its name, it may contain zero or one dot 

character. 

 

Attributes 

---------- 

name : str 

Identifier name. 

""" 

def __init__(self, name): 

Node.__init__(self) 

self.name = name 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

return visitor.visitIdentifier(self.name, self) 

 

def __str__(self): 

return "{name}".format(**vars(self)) 

 

 

class IsIn(Node): 

"""Node representing IN or NOT IN expression. 

 

Attributes 

---------- 

lhs : Node 

Left-hand side of the operation 

values : list of Node 

List of values on the right side. 

not_in : bool 

If `True` then it is NOT IN expression, otherwise it is IN expression. 

""" 

def __init__(self, lhs, values, not_in=False): 

Node.__init__(self, (lhs,) + tuple(values)) 

self.lhs = lhs 

self.values = values 

self.not_in = not_in 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

lhs = self.lhs.visit(visitor) 

values = [value.visit(visitor) for value in self.values] 

return visitor.visitIsIn(lhs, values, self.not_in, self) 

 

def __str__(self): 

values = ", ".join(str(x) for x in self.values) 

not_in = "" 

if self.not_in: 

not_in = "NOT " 

return "{lhs} {not_in}IN ({values})".format(lhs=self.lhs, 

not_in=not_in, 

values=values) 

 

 

class Parens(Node): 

"""Node representing parenthesized expression. 

 

Attributes 

---------- 

expr : Node 

Expression inside parentheses. 

""" 

def __init__(self, expr): 

Node.__init__(self, (expr,)) 

self.expr = expr 

 

def visit(self, visitor): 

# Docstring inherited from Node.visit 

expr = self.expr.visit(visitor) 

return visitor.visitParens(expr, self) 

 

def __str__(self): 

return "({expr})".format(**vars(self))