I don't know how relevant this is; but this sounds like the sort of optimization that pure functional programming allows for - that is, if the compiler ever sees a call like asin(sin($x)), it might optimize the code by just putting $x in there directly, and bypassing both the sin and asin calls - but only because both sin and asin are pure functions (i.e., they don't produce any side effects).
Don't get too hung up on that example. If $x is 2*pi, asin(sin($x)) would return 0.0 and not 2*pi. -- --> From the U S of A, the only socialist country that refuses to admit it. <--
