1 - 4 + 4 is 1, apparently

[_Felix]

but aren't those operators supposed to associate right to left?

[Robert]

Unary plus/minus associativity is right-to-left.

Addition/subtraction is left-to-right.

Robert Wishlaw

[_Felix]

Ah! Thanks.

To ease my embarrassment, here's a genuine error, but it's only in the help files, under the entry for atan2:

Purpose:
Calculates arctangent of y / x.

Returns:
Arctangent of x / y.

[Pelle]

...a bug in v4.50, but corrected for v5.00.