I'm using a mix `span`

and `part`

to try to extract the arguments of a function that I need.

I use a function like $ J ^ mu (1,2,3) $

and I will try to portray this as `J[mu,Range[1,3]]`

or more generally for any index or any number of arguments, `J[index_,Range[1,n_]]`

,

I have to pick the first element each time, that is H. The index of this function, and then I have to select some consecutive elements of the list. I.E; I have to choose terms like `J[index,2,3]`

,

I tried with some variations of `span`

in the `part`

Argument, but I'm having trouble taking just the first variable and some extras.

In particular, I'm trying to program the Berends-Giele recursion relationship for n-gluons.

Any help would be appreciated.

Many Thanks.

To edit:

To show an example:

```
J[mu,1,2,3,4,5][[3;;5]]
```

gives a result of

```
J[2,3,4]
```

as expected. If I take;

```
J[mu,1,2,3,4,5][[1]]
```

I will get

```
mu
```

that is not as expected. What I want is something like saying;

```
J[mu,1,2,3,4,5][[1,3;;4]]
```

what would come back

```
J[mu,3,4]
```

Is that possible with `span`

and `part`

?