On Mon, Oct 12, 2015 at 6:22 AM, Dave Mitchell <davem@iabyn.com> wrote: > On Wed, Oct 07, 2015 at 03:57:26PM -0400, Eric Brine wrote: > > On Wed, Oct 7, 2015 at 4:24 AM, Dave Mitchell <davem@iabyn.com> wrote: > > > > > 2. Make when's behaviour entirely dependent on the *compile-time* class > > > of of its arg. In particular, make 'when (FOO)' have exactly the > following > > > behaviours: > > > > > > FOO condition evaluates to > > > -------------- ---------------------- > > > literal undef !defined($_) > > > numeric const $_ == FOO > > > literal pattern $_ ~= FOO > > > all else $_ eq FOO > > > > > > 3. when { FOO } has condition FOO. > > > > > > For example: > > > > > > use constant ME => "davem"; > > > when (ANS) # equivalent to when { $_ == 42 } > > > > > > > According to your table, shouldn't that be "when { $_ eq ANS }"? ANS > could > > have any value, so when (ANS)" is no different than "when ($x)". There's > no > > "compile-time class" available to study. > > No, its specifically if FOO is a compile-time constant. At compile time > there is no difference between > > when(42) > > and > > use constant FOO; > when(FOO); > > They have both been compiled to a single OP_CONST with a constant SV > attached that can be examined at compile-time for numness. It doesn't matter what code it *results* in. use constant FOO => $x; when (FOO) is no different than when ($x) and we all agree the latter is not workable. FOO is the still the result of an arbitrary expression, even if the expression is evaluated at compile-time. This differs from when ("x") when (4) because that bases behaviour on the *source* code.Thread Previous | Thread Next