There are two things to remember. The first is the match binding thing that tomp mentions in his reply. The second one is that in OCaml, semicolon is a separat

There are two things to remember. The first is the match binding thing that tomp mentions in his reply. The second one is that in OCaml, semicolon is a separator, and not a terminator. In contrast, in C/C++, semicolon is a terminator. If you have an expression, you end it with a ";" just because. This is not the case for OCaml. In OCaml, semicolon is used to separate two sequential expressions where only one expression is expected. Thus, <expr1>;<expr2> is evaluated in sequence, and can be used in a place where only one is expected. For example, if statements have the following syntax: if <expr1> then <expr2> else <expr3> Now if you wanted to do two things (instead of one) in the "then" block, you would simply write if <expr1> then <expr2.1>;<expr2.2> else <expr3> Notice that under these rules if <expr1> then <expr2>; else <expr3> makes no sense. Separators are not terminators. We are used to thinking of ";" as terminators because of C/C++.