Question

In Rebol 2:

>> foo: make object! [a: 10 b: 20]

>> foo/a
== 10

>> foo/b
== 20

>> first foo
== [self a b]

>> second foo
== [make object! [
        a: 10
        b: 20
    ] 10 20]

>> third foo
== [a: 10 b: 20]

>> fourth foo
** Script Error: fourth expected series argument of type:
   series date port tuple event
** Near: fourth foo

So you can pick out of it as if it were a block for values 1, 2, 3. But doing positional selection is right out in Rebol 3:

>> first foo
** Script error: cannot use pick on object! value
** Where: first
** Near: first foo

I gather that this is deprecated now (like picking out of a function to get its parameter list). However, I’m trying to translate some code that says something like:

bar: construct/with (third foo) mumble

(a) What is the point of that code?

(b) How would I translate it to Rebol 3?

Answer 1

a) Construct builds the object without evaluating the spec block. This implies that the spec is of some [set-word! any-type!] form (which it would always be if you are using the body of another object). Construct/with uses a second object (mumble) as the prototype.

b) Object operations appear to have changed as follows:

i) first object is replaced by words-of object

ii) second object is replaced by values-of object

iii) third object is replaced by body-of object or to block! object

Therefore your code can be replaced with:

bar: construct/with body-of foo mumble