RE: Cast vs IntCast

Projects Programming
1

Hi Gang

I'm a little confused what the difference is between the following.

Cast

vs

IntCast

The syntax is slightly different.

(int)x

vs

int(x)

According to the Arduino Reference (int)x translates one variable type to another and forces calculations to be performed in the cast type while int(x) simply converts a value to a int data type.

Am I correct in thinking that (int)x is more capable than int(x)?

float a = 3.142;
int b;
b = int(a); //b is now 3?

OR

float a = 3.142;
int b;
b = (int)a; //b is now 3?

float a = 3.142;
float b;

b = int(a)//b = 3.0?

OR

float a = 3.142;
float b;

b = (int)a//b = 3.0?

Are both of the above legitimate?

Any help would be greatly appreciated?

Cheers

Jase :slight_smile:

2

They are equivalent. This is a "C-style cast":

    (int) b

This is a "functional cast":

    int( b )

Read more here and here.

Your examples are correct, but you should also be aware of implicit casting.

3

Although either will work, I think (int)x is better because consider the case of a cast to unsigned int. You can do this:

(unsigned int)x

but you can't do this:

unsigned int(x)

If you do a mixture of the two your code is harder to read. I do think that int(x) instinctively makes more sense to a beginner who will have already seen that syntax used by functions.

4

Hi -dev

Thanks for getting back to me so quickly. My intention is to break a number into its fractional and integer parts. I thought (possibly incorrectly) that I could explicitly cast my float into an integer to isolate the integer.

float a = 3.142;
float b;

b = int(a);

OR

b = (int)a;

I'm not sure what the difference is between a 'C-style cast' and a functional cast?

Should I be using the function modf? It expects doubles but the Arduino Uno treats doubles and floats the same. I'm unsure how this would work?

Cheers

Jase :slight_smile:

5

Hi pert

Thanks for your input. It seems like a 'C-style cast' has a little more flexibility.

I do agree with you about consistency. It makes your code so much easier to read.

Cheers

Jase :slight_smile:

pert:
Although either will work, I think (int)x is better because consider the case of a cast to unsigned int. You can do this:

(unsigned int)x

but you can't do this:

unsigned int(x)

If you do a mixture of the two your code is harder to read. I do think that int(x) instinctively makes more sense to a beginner who will have already seen that syntax used by functions.

6

pert:
If you do a mixture of the two your code is harder to read. I do think that int(x) instinctively makes more sense to a beginner who will have already seen that syntax used by functions.

When I was teaching this stuff, students got confused with the functional-type cast precisely because it looks like a function. They would ask: "Where can I find the source for the int() function?" I guess it's a matter of preference, but I've been using the K&R style C for almost 40 years now. For me, it's an old-dog-new-trick thing.

7

I like the spirit behind them wanting to look at the source of that function. Maybe it was because they had a good teacher!

8

Hi Gang

Thanks for all the responses. I think I'll go old school C-style cast.

Cheers

Jase :slight_smile:

9

I don't think it makes any sense to cast a float to an int, and store the result in a float. If you want the integer portion of a float, just store the float in an int.