From a string to function handle of a function handle

Hi,

Is it possible to transform a string into a function handle calling another function handle?

More specifically, consider the following simple example

func1=@(x)mean(x)

tmp='@(x)func1(x)+3'

we know that defining

func2=str2func(tmp)

does not work.

Is there any way to create a function handle using tmp that will work?

Thanks

Answer 1

[James Tursa]

func2 = eval(tmp);

[Walter Roberson]

... risky

[James Tursa]

Yep, agreed. If you don't know where that string is coming from and what could be in it or don't trust the source, then eval should probably be avoided.

Answer 2

[Walter Roberson]

tmp='@(x)feval(evalin(''caller'',''func1''),x)+3'

[Patrick Mboma]

Thanks Walter, I guess this would work but at the same time it looks like a very cumbersome way of going about it especially if you have long expressions.

[Walter Roberson]

The basic issue is that str2func() is operating in a context outside your current workspace, so it does not have access to any variables in your workspace. evalin('caller') gives it that access. You would have the same difficulty with a plain variable:

>> A = 5
A =
     5
>> tmp = '@(x) x+A'
tmp =
    '@(x) x+A'
>> func2 = str2func(tmp)
func2 =
  function_handle with value:
    @(x)x+A
>> func2(7)
Undefined function or variable 'A'.
Error in @(x)x+A

str2func always does textual substitutions.