From: | Peter Geoghegan <peter(at)2ndquadrant(dot)com> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Peter Eisentraut <peter_e(at)gmx(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <stark(at)mit(dot)edu>, Bruce Momjian <bruce(at)momjian(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, premanand <kottiprem(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: MySQL search query is not executing in Postgres DB |
Date: | 2012-11-26 00:05:27 |
Message-ID: | CAEYLb_U7iOR1WdcEqEy67=PE=CwfJ=0aG6erZ225DKuv9Ls1Tg@mail.gmail.com |
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On 25 November 2012 23:31, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> The only other programming
> language I know of in which you can define what it means to cast
> between two data types is C++, and it's not generally considered one
> of that languages better features. AFAICT, they have implicit casts
> and explicit casts, but nothing intermediate.
Well, you can make your class copy-constructable by providing a
constructor (and a copy-assignment operator) whose only argument is,
say, an int. In additional to that, you could potentially define a
conversion operator, which will make the class implicitly cast back
into an int. That is kind of a big distinction, because it doesn't
have to go both ways, and in fact it usually doesn't - plenty of
working C++ programmers don't know what a conversion operator is, but
they could all tell you how to get this behaviour:
MyClass foo = 5; // actually calls copy constructor - equivalent to
MyClass foo(5);
foo = 4; // This calls copy assignment operator
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services
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