Current File : //lib/python3/dist-packages/pythran/optimizations/range_loop_unfolding.py
"""
RangeLoopUnfolding turns unfolded range of non unrolled loops back to range.
"""
from pythran.passmanager import Transformation
from pythran.utils import isnum
import gast as ast
class RangeLoopUnfolding(Transformation):
"""
Turns iteration over an incrementing list of literals into a range
>>> import gast as ast
>>> from pythran import passmanager, backend
>>> node = ast.parse("for i in [1,2,3]: print(i)")
>>> pm = passmanager.PassManager("test")
>>> _, node = pm.apply(RangeLoopUnfolding, node)
>>> print(pm.dump(backend.Python, node))
for i in builtins.range(1, 4, 1):
print(i)
"""
def isrange(self, elts):
if not elts:
return None
if not all(isnum(x) and isinstance(x.value, int)
for x in elts):
return None
unboxed_ints = [x.value for x in elts]
start = unboxed_ints[0]
if len(unboxed_ints) == 1:
return start, start + 1, 1
else:
step = unboxed_ints[1] - start
stop = unboxed_ints[-1] + step
if unboxed_ints == list(range(start, stop, step)):
return start, stop, step
else:
return None
def visit_For(self, node):
if isinstance(node.iter, (ast.List, ast.Tuple)):
range_params = self.isrange(node.iter.elts)
if range_params:
node.iter = ast.Call(ast.Attribute(
ast.Name('builtins', ast.Load(), None, None),
'range',
node.iter.ctx),
[ast.Constant(param, None) for param in range_params],
[])
self.update = True
return self.generic_visit(node)
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