"""
R code printer
The RCodePrinter converts single sympy expressions into single R expressions,
using the functions defined in math.h where possible.
"""
from __future__ import print_function, division
from sympy.codegen.ast import Assignment
from sympy.core.compatibility import string_types, range
from sympy.printing.codeprinter import CodePrinter
from sympy.printing.precedence import precedence, PRECEDENCE
from sympy.sets.fancysets import Range
# dictionary mapping sympy function to (argument_conditions, C_function).
# Used in RCodePrinter._print_Function(self)
known_functions = {
#"Abs": [(lambda x: not x.is_integer, "fabs")],
"Abs": "abs",
"sin": "sin",
"cos": "cos",
"tan": "tan",
"asin": "asin",
"acos": "acos",
"atan": "atan",
"atan2": "atan2",
"exp": "exp",
"log": "log",
"erf": "erf",
"sinh": "sinh",
"cosh": "cosh",
"tanh": "tanh",
"asinh": "asinh",
"acosh": "acosh",
"atanh": "atanh",
"floor": "floor",
"ceiling": "ceiling",
"sign": "sign",
"Max": "max",
"Min": "min",
"factorial": "factorial",
"gamma": "gamma",
"digamma": "digamma",
"trigamma": "trigamma",
"beta": "beta",
}
# These are the core reserved words in the R language. Taken from:
# https://cran.r-project.org/doc/manuals/r-release/R-lang.html#Reserved-words
reserved_words = ['if',
'else',
'repeat',
'while',
'function',
'for',
'in',
'next',
'break',
'TRUE',
'FALSE',
'NULL',
'Inf',
'NaN',
'NA',
'NA_integer_',
'NA_real_',
'NA_complex_',
'NA_character_',
'volatile']
[docs]class RCodePrinter(CodePrinter):
"""A printer to convert python expressions to strings of R code"""
printmethod = "_rcode"
language = "R"
_default_settings = {
'order': None,
'full_prec': 'auto',
'precision': 15,
'user_functions': {},
'human': True,
'contract': True,
'dereference': set(),
'error_on_reserved': False,
'reserved_word_suffix': '_',
}
_operators = {
'and': '&',
'or': '|',
'not': '!',
}
_relationals = {
}
def __init__(self, settings={}):
CodePrinter.__init__(self, settings)
self.known_functions = dict(known_functions)
userfuncs = settings.get('user_functions', {})
self.known_functions.update(userfuncs)
self._dereference = set(settings.get('dereference', []))
self.reserved_words = set(reserved_words)
def _rate_index_position(self, p):
return p*5
def _get_statement(self, codestring):
return "%s;" % codestring
def _get_comment(self, text):
return "// {0}".format(text)
def _declare_number_const(self, name, value):
return "{0} = {1};".format(name, value)
def _format_code(self, lines):
return self.indent_code(lines)
def _traverse_matrix_indices(self, mat):
rows, cols = mat.shape
return ((i, j) for i in range(rows) for j in range(cols))
def _get_loop_opening_ending(self, indices):
"""Returns a tuple (open_lines, close_lines) containing lists of codelines
"""
open_lines = []
close_lines = []
loopstart = "for (%(var)s in %(start)s:%(end)s){"
for i in indices:
# R arrays start at 1 and end at dimension
open_lines.append(loopstart % {
'var': self._print(i.label),
'start': self._print(i.lower+1),
'end': self._print(i.upper + 1)})
close_lines.append("}")
return open_lines, close_lines
def _print_Pow(self, expr):
if "Pow" in self.known_functions:
return self._print_Function(expr)
PREC = precedence(expr)
if expr.exp == -1:
return '1.0/%s' % (self.parenthesize(expr.base, PREC))
elif expr.exp == 0.5:
return 'sqrt(%s)' % self._print(expr.base)
else:
return '%s^%s' % (self.parenthesize(expr.base, PREC),
self.parenthesize(expr.exp, PREC))
def _print_Rational(self, expr):
p, q = int(expr.p), int(expr.q)
return '%d.0/%d.0' % (p, q)
def _print_Indexed(self, expr):
inds = [ self._print(i) for i in expr.indices ]
return "%s[%s]" % (self._print(expr.base.label), ", ".join(inds))
def _print_Idx(self, expr):
return self._print(expr.label)
def _print_Exp1(self, expr):
return "exp(1)"
def _print_Pi(self, expr):
return 'pi'
def _print_Infinity(self, expr):
return 'Inf'
def _print_NegativeInfinity(self, expr):
return '-Inf'
def _print_Assignment(self, expr):
from sympy.matrices.expressions.matexpr import MatrixSymbol
from sympy.tensor.indexed import IndexedBase
lhs = expr.lhs
rhs = expr.rhs
# We special case assignments that take multiple lines
#if isinstance(expr.rhs, Piecewise):
# from sympy.functions.elementary.piecewise import Piecewise
# # Here we modify Piecewise so each expression is now
# # an Assignment, and then continue on the print.
# expressions = []
# conditions = []
# for (e, c) in rhs.args:
# expressions.append(Assignment(lhs, e))
# conditions.append(c)
# temp = Piecewise(*zip(expressions, conditions))
# return self._print(temp)
#elif isinstance(lhs, MatrixSymbol):
if isinstance(lhs, MatrixSymbol):
# Here we form an Assignment for each element in the array,
# printing each one.
lines = []
for (i, j) in self._traverse_matrix_indices(lhs):
temp = Assignment(lhs[i, j], rhs[i, j])
code0 = self._print(temp)
lines.append(code0)
return "\n".join(lines)
elif self._settings["contract"] and (lhs.has(IndexedBase) or
rhs.has(IndexedBase)):
# Here we check if there is looping to be done, and if so
# print the required loops.
return self._doprint_loops(rhs, lhs)
else:
lhs_code = self._print(lhs)
rhs_code = self._print(rhs)
return self._get_statement("%s = %s" % (lhs_code, rhs_code))
def _print_Piecewise(self, expr):
# This method is called only for inline if constructs
# Top level piecewise is handled in doprint()
if expr.args[-1].cond == True:
last_line = "%s" % self._print(expr.args[-1].expr)
else:
last_line = "ifelse(%s,%s,NA)" % (self._print(expr.args[-1].cond), self._print(expr.args[-1].expr))
code=last_line
for e, c in reversed(expr.args[:-1]):
code= "ifelse(%s,%s," % (self._print(c), self._print(e))+code+")"
return(code)
def _print_ITE(self, expr):
from sympy.functions import Piecewise
_piecewise = Piecewise((expr.args[1], expr.args[0]), (expr.args[2], True))
return self._print(_piecewise)
def _print_MatrixElement(self, expr):
return "{0}[{1}]".format(self.parenthesize(expr.parent, PRECEDENCE["Atom"],
strict=True), expr.j + expr.i*expr.parent.shape[1])
def _print_Symbol(self, expr):
name = super(RCodePrinter, self)._print_Symbol(expr)
if expr in self._dereference:
return '(*{0})'.format(name)
else:
return name
def _print_Relational(self, expr):
lhs_code = self._print(expr.lhs)
rhs_code = self._print(expr.rhs)
op = expr.rel_op
return ("{0} {1} {2}").format(lhs_code, op, rhs_code)
def _print_sinc(self, expr):
from sympy.functions.elementary.trigonometric import sin
from sympy.core.relational import Ne
from sympy.functions import Piecewise
_piecewise = Piecewise(
(sin(expr.args[0]) / expr.args[0], Ne(expr.args[0], 0)), (1, True))
return self._print(_piecewise)
def _print_AugmentedAssignment(self, expr):
lhs_code = self._print(expr.lhs)
op = expr.op
rhs_code = self._print(expr.rhs)
return "{0} {1} {2};".format(lhs_code, op, rhs_code)
def _print_For(self, expr):
target = self._print(expr.target)
if isinstance(expr.iterable, Range):
start, stop, step = expr.iterable.args
else:
raise NotImplementedError("Only iterable currently supported is Range")
body = self._print(expr.body)
return ('for ({target} = {start}; {target} < {stop}; {target} += '
'{step}) {{\n{body}\n}}').format(target=target, start=start,
stop=stop, step=step, body=body)
[docs] def indent_code(self, code):
"""Accepts a string of code or a list of code lines"""
if isinstance(code, string_types):
code_lines = self.indent_code(code.splitlines(True))
return ''.join(code_lines)
tab = " "
inc_token = ('{', '(', '{\n', '(\n')
dec_token = ('}', ')')
code = [ line.lstrip(' \t') for line in code ]
increase = [ int(any(map(line.endswith, inc_token))) for line in code ]
decrease = [ int(any(map(line.startswith, dec_token)))
for line in code ]
pretty = []
level = 0
for n, line in enumerate(code):
if line == '' or line == '\n':
pretty.append(line)
continue
level -= decrease[n]
pretty.append("%s%s" % (tab*level, line))
level += increase[n]
return pretty
[docs]def rcode(expr, assign_to=None, **settings):
"""Converts an expr to a string of r code
Parameters
==========
expr : Expr
A sympy expression to be converted.
assign_to : optional
When given, the argument is used as the name of the variable to which
the expression is assigned. Can be a string, ``Symbol``,
``MatrixSymbol``, or ``Indexed`` type. This is helpful in case of
line-wrapping, or for expressions that generate multi-line statements.
precision : integer, optional
The precision for numbers such as pi [default=15].
user_functions : dict, optional
A dictionary where the keys are string representations of either
``FunctionClass`` or ``UndefinedFunction`` instances and the values
are their desired R string representations. Alternatively, the
dictionary value can be a list of tuples i.e. [(argument_test,
rfunction_string)] or [(argument_test, rfunction_formater)]. See below
for examples.
human : bool, optional
If True, the result is a single string that may contain some constant
declarations for the number symbols. If False, the same information is
returned in a tuple of (symbols_to_declare, not_supported_functions,
code_text). [default=True].
contract: bool, optional
If True, ``Indexed`` instances are assumed to obey tensor contraction
rules and the corresponding nested loops over indices are generated.
Setting contract=False will not generate loops, instead the user is
responsible to provide values for the indices in the code.
[default=True].
Examples
========
>>> from sympy import rcode, symbols, Rational, sin, ceiling, Abs, Function
>>> x, tau = symbols("x, tau")
>>> rcode((2*tau)**Rational(7, 2))
'8*sqrt(2)*tau^(7.0/2.0)'
>>> rcode(sin(x), assign_to="s")
's = sin(x);'
Simple custom printing can be defined for certain types by passing a
dictionary of {"type" : "function"} to the ``user_functions`` kwarg.
Alternatively, the dictionary value can be a list of tuples i.e.
[(argument_test, cfunction_string)].
>>> custom_functions = {
... "ceiling": "CEIL",
... "Abs": [(lambda x: not x.is_integer, "fabs"),
... (lambda x: x.is_integer, "ABS")],
... "func": "f"
... }
>>> func = Function('func')
>>> rcode(func(Abs(x) + ceiling(x)), user_functions=custom_functions)
'f(fabs(x) + CEIL(x))'
or if the R-function takes a subset of the original arguments:
>>> rcode(2**x + 3**x, user_functions={'Pow': [
... (lambda b, e: b == 2, lambda b, e: 'exp2(%s)' % e),
... (lambda b, e: b != 2, 'pow')]})
'exp2(x) + pow(3, x)'
``Piecewise`` expressions are converted into conditionals. If an
``assign_to`` variable is provided an if statement is created, otherwise
the ternary operator is used. Note that if the ``Piecewise`` lacks a
default term, represented by ``(expr, True)`` then an error will be thrown.
This is to prevent generating an expression that may not evaluate to
anything.
>>> from sympy import Piecewise
>>> expr = Piecewise((x + 1, x > 0), (x, True))
>>> print(rcode(expr, assign_to=tau))
tau = ifelse(x > 0,x + 1,x);
Support for loops is provided through ``Indexed`` types. With
``contract=True`` these expressions will be turned into loops, whereas
``contract=False`` will just print the assignment expression that should be
looped over:
>>> from sympy import Eq, IndexedBase, Idx
>>> len_y = 5
>>> y = IndexedBase('y', shape=(len_y,))
>>> t = IndexedBase('t', shape=(len_y,))
>>> Dy = IndexedBase('Dy', shape=(len_y-1,))
>>> i = Idx('i', len_y-1)
>>> e=Eq(Dy[i], (y[i+1]-y[i])/(t[i+1]-t[i]))
>>> rcode(e.rhs, assign_to=e.lhs, contract=False)
'Dy[i] = (y[i + 1] - y[i])/(t[i + 1] - t[i]);'
Matrices are also supported, but a ``MatrixSymbol`` of the same dimensions
must be provided to ``assign_to``. Note that any expression that can be
generated normally can also exist inside a Matrix:
>>> from sympy import Matrix, MatrixSymbol
>>> mat = Matrix([x**2, Piecewise((x + 1, x > 0), (x, True)), sin(x)])
>>> A = MatrixSymbol('A', 3, 1)
>>> print(rcode(mat, A))
A[0] = x^2;
A[1] = ifelse(x > 0,x + 1,x);
A[2] = sin(x);
"""
return RCodePrinter(settings).doprint(expr, assign_to)
[docs]def print_rcode(expr, **settings):
"""Prints R representation of the given expression."""
print(rcode(expr, **settings))
