(r)
return [r[i] for i in topological_sort((range(len(r)), E))]
Sort replacements `r` so (k1, v1) appears before (k2, v2)
    if k2 is in v1's free symbols. This orders items in the
    way that cse returns its results (hence, in order to use the
    replacements in a substitution option it would make sense
    to reverse the order).

    Examples
    ========

    >>> from sympy.simplify.cse_main import reps_toposort
    >>> from sympy.abc import x, y
    >>> from sympy import Eq
    >>> for l, r in reps_toposort([(x, y + 1), (y, 2)]):
    ...     print(Eq(l, r))
    ...
    y == 2
    x == y + 1
Sort replacements `r` so (k1, v1) appears before (k2, v2)
    if k2 is in v1's free symbols. This orders items in the
    way that cse returns its results (hence, in order to use the
    replacements in a substitution option it would make sense
    to reverse the order).
Sort replacements r so ( k1 v1 ) appears before ( k2 v2 ) if k2 is in v1 s free symbols . This orders items in the way that cse returns its results ( hence in order to use the replacements in a substitution option it would make sense to reverse the order ) .
def reps_toposort(r):
    """Sort replacements `r` so (k1, v1) appears before (k2, v2)
    if k2 is in v1's free symbols. This orders items in the
    way that cse returns its results (hence, in order to use the
    replacements in a substitution option it would make sense
    to reverse the order).

    Examples
    ========

    >>> from sympy.simplify.cse_main import reps_toposort
    >>> from sympy.abc import x, y
    >>> from sympy import Eq
    >>> for l, r in reps_toposort([(x, y + 1), (y, 2)]):
    ...     print(Eq(l, r))
    ...
    y == 2
    x == y + 1

    """
    r = sympify(r)
    E = []
    for c1, (k1, v1) in enumerate(r):
        for c2, (k2, v2) in enumerate(r):
            if k1 in v2.free_symbols:
                E.append((c1, c2))
    return [r[i] for i in topological_sort((range(len(r)), E))]
def reps_toposort ( r ) : r = sympify ( r ) E = [ ] for c1 , ( k1 , v1 ) in enumerate ( r ) : for c2 , ( k2 , v2 ) in enumerate ( r ) : if k1 in v2 . free_symbols : E . append ( ( c1 , c2 ) ) return [ r [ i ] for i in topological_sort ( ( range ( len ( r ) ) , E ) ) ]