Why is airy(3,1) complex? (No numerical round-off in the complex part)

Why does Matlab return a complex number for airy(3,1)?

The result is a pure real, the imaginary part is identically zero (no numerical round off), yet the value is considered complex?

>> format long

>> y = airy(3,1)

y =
   0.932435933392775

>> isreal(y)

ans =
     0

>> format hex

>> imag(y)

ans =
   0000000000000000

Answer 1

[Wayne King]

What release are you using?

>> format long
>> isreal(airy(3,1))

ans =

       1

Answer 2

[David Wilson]

R2012a

[Wayne King]

I've confirmed that behavior in R2012a, but it is fixed in R2012b, let me check the bug reports

[Wayne King]

I don't see it as a bug report David, but the behavior is fixed in 12b, airy(3,1) returns the scalar with attribute real

Answer 3

[Matt Tearle]

Looks like a bug in 12a. If you do

whos y

it shows the class as double (complex), so isreal is working properly, but how the heck it gets a complex y with 0 real part is a mystery to me. It looks like the problem is actually coming from besselmx, which airy calls:

z = besselmx(real('B'),1,1)
whos z

It's fixed in 12b, where airy is now a built-in.