c++ array initialization

Question

float minTime[7]={FLT_MAX};
    for(int i=0;i<7;i++)
        cout << "Min: " << minTime[i] << endl;

Why do I get in the following output :

Min: 3.40282e+038
Min: 0
Min: 0
Min: 0
...

Shoudln't all have the same value as the first one? As it is refered here: C++ Notes

From your link: Missing initialization values use zero If an explicit array size is specified, but an shorter initiliazation list is specified, the unspecified elements are set to zero. — Erik
– Erik, Commented Mar 13, 2011 at 17:21

Community · Accepted Answer · 2017-05-23 12:15:28Z

4

Your linked page says "...the unspecified elements are set to zero."

This is correct; as such, only the first element in your array was specified to be FLT_MAX, the rest are initialized to zero. If you want to set them all to the same value you can use a for-loop, or more succinctly:

std::fill_n(minTime, 7, FLT_MAX);

As a warning, C++ is a hard language. This means lots of people have lots of misinformation, and this is especially easy to find on the internet. You'd be better off learning from a book on our list. (And yes, the ones not on our list are so because they too contain misinformation!)

edited May 23, 2017 at 12:15

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answered Mar 13, 2011 at 17:22

GManNickG

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1 Comment

GManNickG Over a year ago

@doubter: That's okay, it'll happen again and again to all of us. :)

Prasoon Saurav · Accepted Answer · 2011-03-13 17:25:55Z

2

Shoudln't all have the same value as the first one?

Nopes! When an array is partially initialized the non-initialized array elements are value initialized (zero-initialized in this case).

C++03 Section 8.5.1/7

If there are fewer initializers in the list than there are members in the aggregate, then each member not explicitly initialized shall be value-initialized (8.5).
[Example:
struct S { int a; char* b; int c; };
S ss = { 1, "asdf" };
initializes ss.a with 1, ss.b with "asdf", and ss.c with the value of an expression of the form int(), that is, 0. ]

edited Mar 13, 2011 at 17:25

answered Mar 13, 2011 at 17:20

Prasoon Saurav

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3 Comments

doubter Over a year ago

But that wasn't if I'd did: float miniTime[7]={FLT_MAX,FLT_MAX} and the remaining 5 would be 0? If I only set one of the elements all should be the same, or not?

Armen Tsirunyan Over a year ago

Technically, the rest of the elements are value-initialized, not zero-initialized. Not that there is any difference for floats :)

Prasoon Saurav Over a year ago

@Armen : Yes! Added relevant text from the standard.

Asha · Accepted Answer · 2011-03-13 17:53:27Z

1

No, only first value is initialized with the supplied value, other values are value initialized as per standard.

edited Mar 13, 2011 at 17:53

answered Mar 13, 2011 at 17:21

Asha

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1 Comment

Armen Tsirunyan Over a year ago

As per standard, they are value-initialized, not default initialized. Not that there is any difference for POD types, including floats

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