OpenEuphoria

Re: append and &

• Posted by Derek Parnell <ddparnell at bigpond.com> Mar 21, 2002
• 380 views

----- Original Message -----
From: "George Walters" <gwalters at sc.rr.com>
To: "EUforum" <EUforum at topica.com>
Subject: append and &


>
> Can someone explain the difference between these two statements
> -----------------------------
> sequence a
> a = "a"
> for i = 1 to 10
>     a = append(a,"a")
> end for
> ----------------------------
> sequence a
> a = "a"
> for i = 1 to 10
>     a = a & "a"
> end for
> ----------------------------
>
> I'm having some conceptual confusion with results from above as compared
> with 'vectors', 'matrices' from prior languages.


append() always increases the result by exactly one element.

& always increases the results by the length of the source.

In both cases, atoms are considered to have a length of 1 for this exercise.

Thus a = append(b, c) always adds a single element, c, as a new element to
the end of b.
  eg:

    a = {1,2,3}
    a = append(a,a)
      ==> {1,2,3,{1,2,3}} The length increases by 1.
    a = append(a,a)
      ==> {1,2,3,{1,2,3},{1,2,3,{1,2,3}}} The length increases by 1.

And a = b & c always just joins c to the back of b, increasing the length by
how ever long c is.

    a = {1,2,3}
    a = a & a
      ==> {1,2,3,1,2,3} The length increases by 3.
    a = a & a
      ==> {1,2,3,1,2,3,1,2,3,1,2,3} The length increases by 6.

For sequences,  a = append(a,a) is equivalent to  a &= {a}

For atoms, a = append(a,a) is equivalent to a &= a.

-----------
Derek.