Function handle invoking Java reports syntax error?

Why does

d='.'; mylength = length(java.io.File(d).listFiles(org.apache.commons.io.filefilter.WildcardFileFilter('*.dat')))

work, but a function handle for input "d" fail with a syntax error?

 length_func = @(d) length(java.io.File(d).listFiles(org.apache.commons.io.filefilter.WildcardFileFilter('*.dat')))

??? Error: Expression or statement is incorrect--possibly unbalanced (, {, or [.

[Ahmed Fasih]

This following does work:

helper=@(f) f.listFiles(org.apache.commons.io.filefilter.WildcardFileFilter('*.dat'))

length_func = @(d) length(helper(java.io.File(d)))

Answer 1

[Laurens Bakker]

Hi Ahmed,

anonymous functions are not allowed to store any data, and accessing a field of java.io.File(d) probably implicitly does this.

Cheers,

Laurens