Posted Dec 20, 2011 0:57 UTC (Tue) by HelloWorld
In reply to: turing complete
Parent article: Cracks in the Foundation (PHP Advent)
Accusing people of "trolling" when they explain why you're wrong is poor form.
The general idea you had was fine, there are indeed applications which necessarily involve side effects and the lambda calculus doesn't have side effects. But answering individual HTTP requests (remember PHP isn't a web server, it doesn't need to care about the details of how those requests are made, where they come from, or how answers are returned) isn't really one of those applications. Thus the lack of side effects isn't a deal breaker, and my explanation deliberately didn't use them.
And actually, even that wouldn't suffice. Imagine a web server with a hardware random number generator and a web application that allows you to query the xth number generated from now on (where x is supplied by the client). Due to Heisenberg's uncertainty principle, you can't possibly measure the state of the RNG well enough to predict what the xth generated number will be, so you clearly need some kind of side effect for that kind of application.
The reason I didn't write all this stuff earlier is that I just couldn't be bothered to argue with a troll like nybble41. There's simply no value at all in this discussion, and nothing enlightening is going to come out of it (not for me, anyway). The only reason I engaged in it at all is that I don't like being told I'm wrong when I'm not.
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