Create array in a function parameter in C

Question

Is this possible in C or C++? I have a function with the following declaration:

int foo(double*)

And I am trying to do something like this:

foo([] = {1.0, 2.0, 3.0, 4.0});

I know that I can create an array separately, but I am curious if I can do it that way.

Thanks.

What happened when you tried it ?

ApplePie
– ApplePie

2013-12-06 23:24:42 +00:00
Commented Dec 6, 2013 at 23:24 — ApplePie
– ApplePie, Commented Dec 6, 2013 at 23:24
Syntax error. syntax error : '=', using VS 2012.

Pacha
– Pacha

2013-12-06 23:26:02 +00:00
Commented Dec 6, 2013 at 23:26 — Pacha
– Pacha, Commented Dec 6, 2013 at 23:26

user529758 · Accepted Answer · 2013-12-06 23:25:21Z

4

In C: use C99 compound literals:

foo((double[]){ 1.0, 2.0, 3.0, 4.0 });

In C++: (I hate "C/C++" questions!) - I tried this and used C++11 initializer lists in a similar way. However, I'm not entirely confident whether this is legal or results in undefined behavior:

foo(&(std::vector<double> { 1, 2, 3, 4 })[0])

Anyone could confirm this? (compiles with no warnings, runs... that doesn't mean anything, though.)

answered Dec 6, 2013 at 23:25

user529758

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3 Comments

haccks Over a year ago

There should be restriction not to tag same question with both C and C++ tag together.

user529758 Over a year ago

@haccks I was thinking about that today...

haccks Over a year ago

What a coincidence! :)

haccks · Accepted Answer · 2013-12-06 23:32:25Z

0

Yes you can do that by compound literals. C99 allows this feature.

  foo((double[]){1.0, 2.0, 3.0, 4.0});

In this example, the compound literal creates an array (on the fly) containing the four floats.
You may also write this

  foo((double[4]){1.0, 2.0, 3.0, 4.0});

edited Dec 6, 2013 at 23:32

answered Dec 6, 2013 at 23:26

haccks

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2 Comments

piokuc Over a year ago

The paranthesis don't match.

haccks Over a year ago

@piokuc; That's because I copied OP's code and did some changes to it instead of typing :)

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