Re: While Loop
- To: mathgroup at smc.vnet.net
- Subject: [mg123584] Re: While Loop
- From: DrMajorBob <btreat1 at austin.rr.com>
- Date: Mon, 12 Dec 2011 06:42:55 -0500 (EST)
- Delivered-to: l-mathgroup@mail-archive0.wolfram.com
- References: <jbvjus$j47$1@smc.vnet.net> <201112110849.DAA29692@smc.vnet.net>
- Reply-to: drmajorbob at yahoo.com
Nice.
Bobby
On Sun, 11 Dec 2011 02:49:44 -0600, Oleksandr Rasputinov
<oleksandr_rasputinov at hmamail.com> wrote:
> On Sat, 10 Dec 2011 12:39:56 -0000, Joao <joaopereira9 at gmail.com> wrote:
>
>> Hi, everybody
>>
>> Could someone help me regarding the While Loop.
>>
>> While[test,body]
>>
>> In the help "While" it is stated that the test may be evaluated at the
>> end of the loop, instead of at the beginning. However in the tutorial on
>> Loops and Control structures it is stated that the While always
>> evaluates the test at the beginning.
>>
>> I would like to know if it is really possible to evaluate the test
>> inside de While at the end of the loop.
>
> For the syntactical form you give above, test (not "the test", but "the
> expression called test") is always evaluated before body (ditto). This is
> standard in Mathematica in that function arguments normally evaluate from
> right to left. However, what the documentation is saying is that there
> are
> variant forms you can use to have "the test" evaluated after "the body".
> You can, of course, use
>
> While[True, body; If[test, Break[]]]
>
> but I think the clearest way is the one which omits body entirely ("the
> expression called body" is implicitly Null). For example,
>
> i = 5; While[Print[--i]; i > 0]
>
> which prints
>
> 4
> 3
> 2
> 1
> 0
>
> and thus demonstrates that it meets your requirements.
>
--
DrMajorBob at yahoo.com
- References:
- Re: While Loop
- From: "Oleksandr Rasputinov" <oleksandr_rasputinov@hmamail.com>
- Re: While Loop