Re: [PIC] Learning C

But you could use also the function 'isnan', which is easier to 
understand for someone reading your code.

There are also other functions like 'isinf', etc.


Interestingly, a NaN is not greater, nor smaller nor equal to anything, 
not even itself. It is only different than everything.


Cheers,

Isaac


Em 10/11/2024 20:09, smplx escreveu:
> Hi Colin,
>
> You might be intested to know that to check for floating point errors 
> / exceptions in C you would use:
>
> if (x == x)...
> or
> if (x != x)...
>
> where x is a float
>
> e.g.
>     float    x
>
>     x = 1.0 / 0.0;
>
>     if (x != x)
>     {    // x is a NaN which is an error
>     }
>
> Here clearly "x 'is the same as' x" but the test is "x 'is a NaN'".
>
> Friendly Regards
> Sergio
>
> On Sun, 10 Nov 2024, CDB wrote:
>
>> I have always separated the difference of =  and == in C by referring 
>> to the latter as 'is the same as'
>>
>> if (X is the same as Y) then ......  if (X == Y) then
>> x = y       x now contains the value of Y.
>>
>> Colin
>>
>>
>> -- 
>>
>> [email protected]  11 November 2024
>>
>> Hosted by:  www.superdomains.com.au
>>
>> This email is to be considered private if addressed to a named 
>> individual or Personnel Department, and public if addressed to a 
>> blog,  forum or news article.
>>
>>
>>
>> __________________________________
>> Sent from eM Client | www.emclient.com <https://www.emclient.com/get>
>>
>>
>> On 11/11/2024 08:24:15, "smplx" <[email protected]> wrote:
>>
>>>
>>>
>>> On Sun, 10 Nov 2024, Neil wrote:
>>>
>>>> Agree with a couple things from other comments such as C being 
>>>> high-level assembler and using a PC at first (you can just use gcc 
>>>> already on Linux).
>>>>
>>>> Already knowing a structured language is very helpful.
>>>> But IMO you'll have to wrap your head around pointers, which can 
>>>> get confusing. I find this C visualizer very helpful for figuring 
>>>> out some algorithm... https://pythontutor.com/c.html
>>>>
>>>> One more note: = != ==
>>>> Or in other words, the equal sign ( = ) and the double equal size ( 
>>>> == ) are very different things in C. The first assigns a value and 
>>>> the other compares values. But people new to C will invariably use 
>>>> a single equal for a comparison and the code is true every time, as 
>>>> C will compile it as valid code, do the assignment, then the 
>>>> comparison. You have been warned ;P
>>>
>>> Sorry to wade in here but:
>>>
>>> if (y = x)...
>>>
>>> assigns x to y then compares the result to 0. 0 is nomally taken to
>>> mean false and "not 0" as true. So it is almost alway true except in 
>>> the case where x is 0.
>>>
>>> I'm not sure what happens if x and y are floats and x is a NaN or if 
>>> x and y are structures.
>>>
>>> if you're looking for a real headache try debugging a program that 
>>> contains:
>>>
>>> if (! x == y)...
>>>
>>> Trying to learn C on bare metal is like trying to learn to fly by 
>>> crashing a lot. It's a lot quicker and easier if you learn on a 
>>> simulator.
>>>
>>> Friendly Regards
>>> Sergio Masci
>>>
>>> -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>>> View/change your membership options at
>>> https://mailman.mit.edu/mailman/listinfo/piclist
>> -- 
>> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
>> View/change your membership options at
>> https://mailman.mit.edu/mailman/listinfo/piclist
>>

-- 
O software antivírus Avast realizou uma checagem de vírus neste e-mail.
www.avast.com
-- 
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
https://mailman.mit.edu/mailman/listinfo/piclist