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Asked by Igor
on 20 May 2011

I don't see differences between... but - maybe @fun is more wide than inline-function

>> a

a =

1

>> x=1:10

x =

1 2 3 4 5 6 7 8 9 10

>> y=@(x) x.^a

y =

@(x)x.^a

>> y(x)

ans =

1 2 3 4 5 6 7 8 9 10

>> a=3

a =

3

>> y(x)

ans =

1 2 3 4 5 6 7 8 9 10

>> z=inline('x.^a','x')

z =

Inline function: z(x) = x.^a

>> z(x)

??? Error using ==> inlineeval at 15 Error in inline expression ==> x.^a Undefined function or variable 'a'.

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Answer by Oleg Komarov
on 20 May 2011

Accepted answer

**Step 1** - define anonymous function in constant *a* and variable *x*:

a = 1; y = @(x) x.^a;

**Step 2** - change constant in the workspace, but the anonymous function remains unchanged since *a* was taken as a parameter in step 1

a = 3; y(x)

**Step 3** - in both cases the constant *a* is not defined at the moment the anonymous and inline fcns are created, thus the error in **both** cases

clear all y = @(x) x.^a; y(1)

z = inline('x.^a','x') z(x)

**Step 4** alternatives

y = @(x,a) x.^a; y(1,2)

z = inline('x.^a','x','a') z(1,2)

inline is an eval wrapper and is much slower than anonymous fcns.

Show 3 older comments

Titus Edelhofer
on 20 May 2011

Hi Igor,

for the "why": anonymous functions were "invented" as a replacement for the (somewhat ugly) inline.

Anonymous functions are much more robust then inline, same holds for using function handles in general instead of strings. Your example shows the difference: the function

@(x) x.^a

captures a at this very moment. What ever happens to a does not make a difference. This is in line with general behaviour: if you write

a = 42

x = 2*a;

a = 1;

you won't expect x to be 2. If a is indeed to be variable, use step 4.

Igor
on 20 May 2011

I asked another "why" -- concerning inline.

The error is due to "not enough input args" (like this), OR due to parser at calling ">> z(x)" hasn't recognized "a" as a fact variable.

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