Mixing
Definition: expressions that can be evaluated versus those that can't
Clash Royale CLAN TAG #URR8PPP up vote 0 down vote favorite Suppose I have an expression $y + f(x)$, and I know $y in mathbb R, x in X$ and $f$ is an arbitrary function from $X$ to the reals. If I know $y$ and $x$ but don't know $f$, I can't evaluate the expression $y + f(x)$. At least, not completely. But once I know $f$, (say $f(z) = z^2$), then I can evaluate the expression $y + f(x)$. Is there a name for the difference between these two circumstances? computability symbolic-computation share | cite | improve this question asked Aug 6 at 23:26 alexpghayes 101 3 In maths, there is no such instance where you can not evaluate a function. At he very least, I can always say that the evaluation of $f$ at $x$ is $f(x)$. Actually, I do not really see in what context your interrogation arises. Is there a context where this matters? – Suzet Aug 6 at 23:53 @Suzet That is not true. You can easily define a relation, for wh