package void invert(double[] from) {

            from[] *= 7.0;

            pragma(msg, typeof(invert)); // output void(double[] from)

            pragma(msg, is(void function (double[]))); // true void function (double[]) is a type

            pragma(msg, is(typeof(invert) == function)); // true typeof invert is a function

            pragma(msg, is(typeof(invert) == void function(double[]))); // false ???

            // what we see here is that is expressions are broken.

            // pragma(msg, is(typeof(invert) == R F (A), R, A, F)); // if it's not a function let F be a free symbol as well

                                                                 // answer: expected identifier `F` in declarator

                                                                 // this is a parser error

                                                                 // therefore the line had to be commented out

}

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