A question about expressions...

[Guest]

  When »f(x)« is an expression and »x« is a subexpression, I
  think it is save to say that for each evaluation of »f(x)«,
  the subexpression »x« is evaluated once, ...

How does this fit expressions like »x*x«?

 

[Keith Thompson]

How does this fit expressions like »x*x«?

The expression ``x*x'' has two subexpressions, both of which look
like ``x''. Each of these two subexpressions is evaluated once
during the evaluation of ``x*x''. Unless x is volatile, the compiler
is free to generate code that evaluates x only once (or that doesn't
evaluate the expression at all) -- as long as the result is the same.