def _loop_range(
itervar: str, inedges: List[gr.Edge],
condition: sp.Expr) -> Optional[Tuple[sp.Expr, sp.Expr, sp.Expr]]:
"""
Finds loop range from state machine.
:param itersym: String representing the iteration variable.
:param inedges: Incoming edges into guard state (length must be 2).
:param condition: Condition as sympy expression.
:return: A three-tuple of (start, end, stride) expressions, or None if
proper for-loop was not detected. ``end`` is inclusive.
"""
# Find starting expression and stride
itersym = symbolic.symbol(itervar)
if (itersym in symbolic.pystr_to_symbolic(
inedges[0].data.assignments[itervar]).free_symbols
and itersym not in symbolic.pystr_to_symbolic(
inedges[1].data.assignments[itervar]).free_symbols):
stride = (symbolic.pystr_to_symbolic(
inedges[0].data.assignments[itervar]) - itersym)
start = symbolic.pystr_to_symbolic(
inedges[1].data.assignments[itervar])
elif (itersym in symbolic.pystr_to_symbolic(
inedges[1].data.assignments[itervar]).free_symbols
and itersym not in symbolic.pystr_to_symbolic(
inedges[0].data.assignments[itervar]).free_symbols):
stride = (symbolic.pystr_to_symbolic(
inedges[1].data.assignments[itervar]) - itersym)
start = symbolic.pystr_to_symbolic(
inedges[0].data.assignments[itervar])
else:
return None
# Find condition by matching expressions
end: Optional[sp.Expr] = None
a = sp.Wild('a')
match = condition.match(itersym < a)
if match:
end = match[a] - 1
if end is None:
match = condition.match(itersym <= a)
if match:
end = match[a]
if end is None:
match = condition.match(itersym > a)
if match:
end = match[a] + 1
if end is None:
match = condition.match(itersym >= a)
if match:
end = match[a]
if end is None: # No match found
return None
return start, end, stride
