Re: Why raises this an error? :-(

[Jeffrey Carter <jrcarter@acm.org>]

Kai Gl�sner wrote:
> 
> This:
> 
>     Alt_D := (-8.0/4.0) ** 2.0;
> 
> raises this:
> 
>     raised ADA.NUMERICS.ARGUMENT_ERROR : a-ngelfu.adb:111 instantiated
> at a-nuelfu.ads:20
> 
> This:
> 
>     Alt_D := -2.0 ** 2.0;
> 
> works fine!

Exponentiation has higher precedence than unary minus (ARM 4.5), so this
is equivalent to

Alt_D := -(2.0 ** 2.0);

ARM A.5.1 says that Argument_Error is raised "by the exponentiation
operator, when the value of the left operand is negative". This is the
case in your first example.

Since your exponent is an integer value, you can avoid this restriction
by using the predefined exponentiation operator for floating-point
types:

Alt_D := (-8.0 / 4.0) ** 2;

-- 
Jeff Carter
"Your mother was a hamster and your father smelt of elderberries."
Monty Python & the Holy Grail