On 8/1/14, 9:46 PM, Chris Cain wrote:
On Saturday, 2 August 2014 at 04:28:33 UTC, Timon Gehr wrote:
On 08/02/2014 06:11 AM, Chris Cain wrote:
On Saturday, 2 August 2014 at 03:40:47 UTC, Timon Gehr wrote:
I already googled 'statement of fact' myself earlier, and found the
wikipedia entry for 'fact', that I quoted back then:
http://en.wikipedia.org/wiki/Fact
"The usual test for a statement of fact is verifiability, that is,
whether it can be demonstrated to correspond to experience."
I.e. in order to determine whether something is a statement of fact,
one should verify it. Do you agree that it is saying this?
I'll just do this real quick, because it's a really easy one to show the
problem with.
Google "verifiable" ->
http://www.merriam-webster.com/dictionary/verifiable -> "capable of
being verified"
...
Great, now we are getting somewhere.
http://dictionary.reference.com/browse/verify?s=t
"to prove the truth of, as by evidence or testimony; confirm;
substantiate: Events verified his prediction."
I understand "capable of being verified" as "there is a way to verify
this" which is the same as "this can be proven" which would imply
"this is true".
What's wrong here?
The fact that you assume that something "can be proven" means it "has
been proven" or "must be proven". Because you don't necessarily have to
prove it, it doesn't necessarily mean it is true. It's a statement that
you are suggesting is true but *could* be falsified/shown to be
false/verified/verified to be false.
The mere fact that asserts take in expressions show that something "can
be proven", but there is no implication that it, therefore, must be
proven. If you put an expression in an assert and it successfully
compiles, you've made a statement of fact. It's useful that it is
checked/proven in debug builds but not surprising that it's required to
by definition.
That is, it's something that has some ability to be verified. Thus, 1==2
is "verifiable" (it can be shown to be either true or false).
...
If I can verify 1==2, I would prove 1==2, as per the definition above,
no?
No. You can verify it but find it to be false. Your proof would show it
to be false. The fact that you can write a proof showing it to be false
is a proof that it was verifiable in the first place.
It is possible that this is indeed what it tries to communicate.
Thanks for bearing with me in any case!
No problem. :)
But as I wrote in my previous post, now this brings up the issue that
if an assertion is a statement of fact, then it is not necessarily true.
Why is it now obvious that it should be considered true?
For the same reason that all of the other things you type into a program
is accepted by a program.
`if(...)` ... would it be strange if your program doubted that you
really want to execute the block the if statement refers to? Of course
it would.
Basically, you're a god and what you say to do is law in computer
programming. By default you expect the computer to not doubt you and to
follow what you say. It's not like a person who will question your
assertions and ask you to prove them or double check them for you.
Though, the fact that it will double check them for you is helpful in
debug builds, so it's an obvious enhancement for debugging purposes.
Since assert is you making a statement of fact, it's logical that it
should, by default, accept what you say just like it accepts every other
command you give it.
If you're wrong... well, it's just like if you're wrong about your if
statements or if you call the wrong function or pass in the wrong
variables. You'll get incorrect program behavior. Unlike those other
things, since it's verifiable, there exists some sort of configurations
where the program can be helpful to you by verifying your assertions.
I don't think there's ever been a more majestic thread in the history of
this forum. Probably up there with the best of them anywhere and
anytime. It's become officially an Epic Debate.
Andrei
