No Òreferential transparencyÓ
lIn a functional language
f(X) * f(X)
is same value as
Y = f(X), Y*Y

lIn an imperative language, we cannot make this claim; f(X) may have Òside-effectsÓ apart from the production of a value.  (In some cases, it could even modify X.
an example of Òreferential transparencyÓ