array of structures dynamic allocation

Question

1.00/5 (1 vote)

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Hello everyone,
will someone please explain to me how to dynamically allocate and array of structures
for example this structure

C++

typedef struct
{
   float angle;   //current servo angle
   unsigned int16 width_count;

   float min_angle;  //min achievable angle
   float max_angle;  //max achievable angle

   int16 min_uswidth;
   int16 max_uswidth;
}servo_motor;

servo_motor servo[4];

thanks in advance,
z3ngew

Posted 12-Aug-13 10:18am

z3ngew

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3 solutions

Solution 2

Here: 7.2 Passing Arrays to Functions[^] you'll find an example

Posted 12-Aug-13 11:00am

Maciej Los

Comments

Sergey Alexandrovich Kryukov 12-Aug-13 17:04pm

That certainly would answer the question, my 5, but... where did you find such an ugly manual?! Code samples are formatted as bitmap images, with all the re-sample distortions. People apparently are not capable of simple HTML formatting, how can they teach programming?
—SA

Maciej Los 12-Aug-13 17:09pm

Thank you, Sergey ;)
You know, where i found it ;)

Sergey Alexandrovich Kryukov 12-Aug-13 17:22pm

Well, come to think about, I do, still weird... :-)
—SA

Maciej Los 12-Aug-13 17:24pm

;)

Solution 3

i found a good answer here
http://cboard.cprogramming.com/cplusplus-programming/80630-passing-struct-function-reference.html[^]

Posted 12-Aug-13 11:01am

z3ngew

Comments

Sergey Alexandrovich Kryukov 12-Aug-13 17:24pm

But then, C++ or C? Passing be reference is the one of the distinct C++, not C features. But this is not a problem. In C, you can pass pointers by value. I already answered your question...
—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2013-08-12T10:26:00

Solution 1

It's malloc, please see:
http://www.cplusplus.com/forum/articles/416/[^].

Please don't forget free.

Why do you thing your allocation should be dynamic? You don't have variable number of structures; in your code, it's the immediate constant 4, which is, by the way, always bad. You should have explicit const. In this case, you can simply declare the array, and it will be allocated on stack and not removed until you leave for a upper-level stack frame.

—SA

Posted 12-Aug-13 10:26am

Sergey Alexandrovich Kryukov

Updated 12-Aug-13 10:29am

v2

Comments

z3ngew 12-Aug-13 16:32pm

I am sorry, i asked the wrong question, it should be How to pass array of struct or or an item of array struct in a function.

Thanks in advance

Sergey Alexandrovich Kryukov 12-Aug-13 16:34pm

You pass a pointer to the first element of array, what's the problem? This is the same as to pass servo, which is if the type servo_motor[].
After all, grab any C textbook and read about it all at once, you will avoid wasting so much time on those questions...
—SA

Maciej Los 12-Aug-13 17:00pm

+5!

Sergey Alexandrovich Kryukov 12-Aug-13 17:02pm

Thank you, Maciej.
—SA

pasztorpisti 12-Aug-13 23:33pm

+5. Recently a collegue found a hardcoded constant in one of my routines I've written in haste. It was 42. Of course when he asked me about some more info I told him that "Its the meaning of life!". :-) Finally we figured out that it was the length of the textual representation of a 160bit sha1 hash + the "\r\n" newline but it took some time regardless of the short size of code that contained it.

Sergey Alexandrovich Kryukov 12-Aug-13 23:49pm

Than you...
42?! This is so memetic. :-)
—SA

pasztorpisti 13-Aug-13 0:16am

Nothing is perfect, I often write small "throw-out" style programs and python scripts in a few minutes and in that case the result is often far from beautiful. The problem comes if a lazy programmer finds one of them in the hope of saving a bit of effort... :-)

Sergey Alexandrovich Kryukov 13-Aug-13 1:52am

Ultimately, this is related to the sense of measure, and this is not simple as it requires some prediction skills, intuition based on formidable experience and the ability to take into account enormous number of factors which cannot physically be help in one brain at once...

Some cases are quite obvious though, especially apparently sloppy ones... :-)

—SA

Herbisaurus 13-Aug-13 2:26am

*****

Sergey Alexandrovich Kryukov 13-Aug-13 2:33am

Thank you,
—SA