Is there any particular reason why having a constructor serve a dual role as a factory is a bad idea?

It's largely a matter of convention and expectation. When I write 

   my $frob = new Frob();

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I expect to get a Frob, and future readers of the code might reasonably expect that $frob will hold an instance of Frob. But if I write 
    my $frob = Frob::makeFrob();

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there is no such assumption. Nobody is misled. At most, the assumption is that $frob will get a Frob or a subclass of Frob.

Having new work consistently 99% of the time is a bad thing. It lulls people into traps.

In reply to Re: Constructor/Factory Orthodoxy by dws
in thread Constructor/Factory Orthodoxy by mojotoad

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