(-) precedence

[KeithB]

Not a new problem!
From Kernighan and Plauger "The Elements of Programming Style":

"A more insidious operator ambiguity occurs in this expression from an arctangent routine:
TERM = TERM*(-X**2)/DENOM

Is X negated and then squared, or squared and then negated? Fortran reference manuals seldom treat such fine points in detail; this may be a hard question to answer without running a test program. As a matter of fact the ANSI standard for Fortran calls for the latter interpretation (fortunate in this case) - the variable X is squared and then negated - but the line should still be rewritten as:
TERM = -TERM * X**2 / DENOM

The first form invites misunderstanding on the part of the reader, if not the compiler. Unless reader and compiler both understand the writer, the program is not communicating properly.

[Rule of Thumb] Parenthesize to avoid ambiguity."