# Use of semi-colons in If[]

This is the code in Mathematica:

h[x_] := (If[x > 5, Return[big]]; t = x^3; Return[t - 7])


I fully understand what the code does, with h[4]=4^3-7=57 and h[6]=h[7]=big but I have the following issues:

1. h[x_] does not function if I remove the brackets () ie h[x_]If[x > 5, Return[big]]; t = x^3; Return[t - 7] , what is the function of () in the code?
2. Can someone also explain the significance of the semi-colons in this code, and what is it used instead of commas (which make the code not work). What are the benefits of using ; instead of , in code?
• The code isn't that great; among other things, you have a global t in there which can be problematic if you're using t somewhere else. Try h[x_] := Block[{t}, If[x > 5, big, t = x^3; t - 7]] (but even that is not the best way to do it). Also, look up CompoundExpression[]. – J. M. will be back soon Oct 14 '18 at 18:18
• function definition has a high priority. Without the () the function definition would end at the first semicolon. With the () the function definition is the whole line. The If[] tests x and potentially bails out with the value big. If it doesn't bail out then the t=x^3;Return[t-7] is all done. Be cautious with Return because people have reported problems with that. – Bill Oct 14 '18 at 18:21

h[x_] := If[x > 5, big, x^3 - 7]

h /@ Range[8]

• Nit-picky: To get exactly the same functionality, you'd want something like If[TrueQ[x > 5], big, x^3 - 7], so that h[z] would return z^3 - 7 instead of an If[] statement. But I expect the OP hasn't thought through that case yet and is assuming x is a real number. – Michael E2 Oct 14 '18 at 21:41