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This chapter is from the book

This chapter is from the book

2.2 Statement Termination

In Java and C++, every statement ends with a semicolon. In Scala—like in JavaScript and other scripting languages—a semicolon is never required if it falls just before the end of the line. A semicolon is also optional before an }, an else, and similar locations where it is clear from context that the end of a statement has been reached.

However, if you want to have more than one statement on a single line, you need to separate them with semicolons. For example,

if (n > 0) { r = r * n; n -= 1 }

A semicolon is needed to separate r = r * x and n -= 1. Because of the }, no semicolon is needed after the second statement.

If you want to continue a long statement over two lines, you need to make sure that the first line ends in a symbol that cannot be the end of a statement. An operator is often a good choice:

s = s0 + (v - v0) * t + // The + tells the parser that this is not the end
  0.5 * (a - a0) * t * t

In practice, long expressions usually involve function or method calls, and then you don’t need to worry much—after an opening (, the compiler won’t infer the end of a statement until it has seen the matching ).

In the same spirit, Scala programmers favor the Kernighan & Ritchie brace style:

if (n > 0) {
  r = r * n
  n -= 1
}

The line ending with a { sends a clear signal that there is more to come.

Many programmers coming from Java or C++ are initially uncomfortable about omitting semicolons. If you prefer to have them, just put them in—they do no harm.

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