Smarter way of doing array initialization?

Question

I need to initialize a fixes size arrays quite often, like so:

for( uint16_t q=0; q<SIZE; q++ ) 
    array[q]=value;

Array is defined as float array[SIZE];

Is there a nicer way of doing this, replacing with a macro or similar?

p.s. Not allowed to use mem___ calls.

What nicer than this and without `memset` or `memcpy`? What type is `array`? — i486, Nov 24 '16 at 13:36
Is this `value` known at compile time or you get it run time? — Swanand, Nov 24 '16 at 13:44
This code isn't doing initialization, it is doing assignment. What are you looking for, initialization or assignment? — Lundin, Nov 24 '16 at 14:32
Definitely not a duplicate, I didn't find anwer there. Please reopen. — Danijel, Nov 24 '16 at 14:47
The "possible duplicate" is totaly different question. People, I am not asking how to "initialize all members of an array to the same value", but how to write a nice code that does the same thing. — Danijel, Nov 24 '16 at 14:49
@Danijel Again as Michael Walz said, define "Nice code"... It varies from person to person... For me, what you have is nice... — Swanand, Nov 24 '16 at 15:12
But in the question you ask how to do "array initialization", not about "code that does the same thing". If you find that nice, define a macro to do it for you — phuclv, Nov 25 '16 at 03:32

score 1 · Answer 1 · answered Nov 24 '16 at 13:47

1

C doesn't have built-in way to initialize the entire array to some non-zero value.

If you use GCC, it has Designated Initializers extension. You can use it like:

float widths[] = { [0 ... 99] = 3.14 };

This set all of the elements to 3.14.

answered Nov 24 '16 at 13:47

Nikita

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freestyle · Accepted Answer · 2018-03-28T09:41:56.463

0

With preprocessor you can do like this:

#define NMEMBERS(x) (sizeof(x)/sizeof(*(x)))
#define ARRSET(arr, val) \
    do { \
        size_t i; \
        for (i = 0; i < NMEMBERS(arr); ++i) \
            (arr)[i] = val; \
    } while (0)

float array[SIZE], val = 0.67f;
ARRSET(array, val);

edited Mar 28 '18 at 09:41

answered Nov 24 '16 at 13:49

freestyle

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Why would you write such an ugly macro for such a simple thing? Just write a plain for loop, end of story. There's no need to obfuscate the code to oblivion. – Lundin Nov 24 '16 at 14:39
Imagine dozen of those loops. This looks nicer: `INITIALIZE(myarr, SIZE, 0.0f);` don't you think. – Danijel Nov 24 '16 at 14:43
@Danijel No it looks really bad. C programmers understand C code, they don't understand "my private, secret macro language". There exist no way in C that lets you write this more elegantly than `for(size_t i=0; i – Lundin Nov 24 '16 at 14:44
What's ugly? You can make convention about naming of macro-functions so that you would recognize them in the code. What are the problems? The task is simple, I need an array initialization function, the amount of which is known by the compiler. I don't want write simple loop every time when I need that. – freestyle Nov 24 '16 at 15:27
1

@Danijel You can have two variants: `ARRNSET(arr, size, 0,0f)` and `ARRSET(arr, 0.0f)` – freestyle Nov 24 '16 at 15:46

Smarter way of doing array initialization?

2 Answers2