from sympy.external import import_module
lfortran = import_module('lfortran')
if lfortran:
from sympy.codegen.ast import (Variable, IntBaseType, FloatBaseType, String,
Return, FunctionDefinition, Assignment)
from sympy.core import Add, Mul, Integer, Float
from sympy.core.symbol import Symbol
asr_mod = lfortran.asr
asr = lfortran.asr.asr
src_to_ast = lfortran.ast.src_to_ast
ast_to_asr = lfortran.semantic.ast_to_asr.ast_to_asr
"""
This module contains all the necessary Classes and Function used to Parse
Fortran code into SymPy expression
The module and its API are currently under development and experimental.
It is also dependent on LFortran for the ASR that is converted to SymPy syntax
which is also under development.
The module only supports the features currently supported by the LFortran ASR
which will be updated as the development of LFortran and this module progresses
You might find unexpected bugs and exceptions while using the module, feel free
to report them to the SymPy Issue Tracker
The API for the module might also change while in development if better and
more effective ways are discovered for the process
Features Supported
==================
- Variable Declarations (integers and reals)
- Function Definitions
- Assignments and Basic Binary Operations
Notes
=====
The module depends on an external dependency
LFortran : Required to parse Fortran source code into ASR
References
==========
.. [1] https://github.com/sympy/sympy/issues
.. [2] https://gitlab.com/lfortran/lfortran
.. [3] https://docs.lfortran.org/
"""
class ASR2PyVisitor(asr.ASTVisitor): # type: ignore
"""
Visitor Class for LFortran ASR
It is a Visitor class derived from asr.ASRVisitor which visits all the
nodes of the LFortran ASR and creates corresponding AST node for each
ASR node
"""
def __init__(self):
"""Initialize the Parser"""
self._py_ast = []
def visit_TranslationUnit(self, node):
"""
Function to visit all the elements of the Translation Unit
created by LFortran ASR
"""
for s in node.global_scope.symbols:
sym = node.global_scope.symbols[s]
self.visit(sym)
for item in node.items:
self.visit(item)
def visit_Assignment(self, node):
"""Visitor Function for Assignment
Visits each Assignment is the LFortran ASR and creates corresponding
assignment for SymPy.
Notes
=====
The function currently only supports variable assignment and binary
operation assignments of varying multitudes. Any type of numberS or
array is not supported.
Raises
======
NotImplementedError() when called for Numeric assignments or Arrays
"""
# TODO: Arithmetic Assignment
if isinstance(node.target, asr.Variable):
target = node.target
value = node.value
if isinstance(value, asr.Variable):
new_node = Assignment(
Variable(
target.name
),
Variable(
value.name
)
)
elif (type(value) == asr.BinOp):
exp_ast = call_visitor(value)
for expr in exp_ast:
new_node = Assignment(
Variable(target.name),
expr
)
else:
raise NotImplementedError("Numeric assignments not supported")
else:
raise NotImplementedError("Arrays not supported")
self._py_ast.append(new_node)
def visit_BinOp(self, node):
"""Visitor Function for Binary Operations
Visits each binary operation present in the LFortran ASR like addition,
subtraction, multiplication, division and creates the corresponding
operation node in SymPy's AST
In case of more than one binary operations, the function calls the
call_visitor() function on the child nodes of the binary operations
recursively until all the operations have been processed.
Notes
=====
The function currently only supports binary operations with Variables
or other binary operations. Numerics are not supported as of yet.
Raises
======
NotImplementedError() when called for Numeric assignments
"""
# TODO: Integer Binary Operations
op = node.op
lhs = node.left
rhs = node.right
if (type(lhs) == asr.Variable):
left_value = Symbol(lhs.name)
elif(type(lhs) == asr.BinOp):
l_exp_ast = call_visitor(lhs)
for exp in l_exp_ast:
left_value = exp
else:
raise NotImplementedError("Numbers Currently not supported")
if (type(rhs) == asr.Variable):
right_value = Symbol(rhs.name)
elif(type(rhs) == asr.BinOp):
r_exp_ast = call_visitor(rhs)
for exp in r_exp_ast:
right_value = exp
else:
raise NotImplementedError("Numbers Currently not supported")
if isinstance(op, asr.Add):
new_node = Add(left_value, right_value)
elif isinstance(op, asr.Sub):
new_node = Add(left_value, -right_value)
elif isinstance(op, asr.Div):
new_node = Mul(left_value, 1/right_value)
elif isinstance(op, asr.Mul):
new_node = Mul(left_value, right_value)
self._py_ast.append(new_node)
def visit_Variable(self, node):
"""Visitor Function for Variable Declaration
Visits each variable declaration present in the ASR and creates a
Symbol declaration for each variable
Notes
=====
The functions currently only support declaration of integer and
real variables. Other data types are still under development.
Raises
======
NotImplementedError() when called for unsupported data types
"""
if isinstance(node.type, asr.Integer):
var_type = IntBaseType(String('integer'))
value = Integer(0)
elif isinstance(node.type, asr.Real):
var_type = FloatBaseType(String('real'))
value = Float(0.0)
else:
raise NotImplementedError("Data type not supported")
if not (node.intent == 'in'):
new_node = Variable(
node.name
).as_Declaration(
type = var_type,
value = value
)
self._py_ast.append(new_node)
def visit_Sequence(self, seq):
"""Visitor Function for code sequence
Visits a code sequence/ block and calls the visitor function on all the
children of the code block to create corresponding code in python
"""
if seq is not None:
for node in seq:
self._py_ast.append(call_visitor(node))
def visit_Num(self, node):
"""Visitor Function for Numbers in ASR
This function is currently under development and will be updated
with improvements in the LFortran ASR
"""
# TODO:Numbers when the LFortran ASR is updated
# self._py_ast.append(Integer(node.n))
pass
def visit_Function(self, node):
"""Visitor Function for function Definitions
Visits each function definition present in the ASR and creates a
function definition node in the Python AST with all the elements of the
given function
The functions declare all the variables required as SymPy symbols in
the function before the function definition
This function also the call_visior_function to parse the contents of
the function body
"""
# TODO: Return statement, variable declaration
fn_args = [Variable(arg_iter.name) for arg_iter in node.args]
fn_body = []
fn_name = node.name
for i in node.body:
fn_ast = call_visitor(i)
try:
fn_body_expr = fn_ast
except UnboundLocalError:
fn_body_expr = []
for sym in node.symtab.symbols:
decl = call_visitor(node.symtab.symbols[sym])
for symbols in decl:
fn_body.append(symbols)
for elem in fn_body_expr:
fn_body.append(elem)
fn_body.append(
Return(
Variable(
node.return_var.name
)
)
)
if isinstance(node.return_var.type, asr.Integer):
ret_type = IntBaseType(String('integer'))
elif isinstance(node.return_var.type, asr.Real):
ret_type = FloatBaseType(String('real'))
else:
raise NotImplementedError("Data type not supported")
new_node = FunctionDefinition(
return_type = ret_type,
name = fn_name,
parameters = fn_args,
body = fn_body
)
self._py_ast.append(new_node)
def ret_ast(self):
"""Returns the AST nodes"""
return self._py_ast
else:
class ASR2PyVisitor(): # type: ignore
def __init__(self, *args, **kwargs):
raise ImportError('lfortran not available')
def call_visitor(fort_node):
"""Calls the AST Visitor on the Module
This function is used to call the AST visitor for a program or module
It imports all the required modules and calls the visit() function
on the given node
Parameters
==========
fort_node : LFortran ASR object
Node for the operation for which the NodeVisitor is called
Returns
=======
res_ast : list
list of SymPy AST Nodes
"""
v = ASR2PyVisitor()
v.visit(fort_node)
res_ast = v.ret_ast()
return res_ast
def src_to_sympy(src):
"""Wrapper function to convert the given Fortran source code to SymPy Expressions
Parameters
==========
src : string
A string with the Fortran source code
Returns
=======
py_src : string
A string with the Python source code compatible with SymPy
"""
a_ast = src_to_ast(src, translation_unit=False)
a = ast_to_asr(a_ast)
py_src = call_visitor(a)
return py_src