On Thu, 10 Jan 2008, Martin Rubey wrote:
| Dear Gaby,
|
| I saw you implemented map!$Stack as follows:
|
| map!(f: S -> S, s: %) == -- from HOAGG
| map!(f, deref s)$List(S)
| s
|
| I have two questions:
|
| 1) why didn't you say
|
| map!(f: S -> S, s: %) == ref map!(f, deref s)$List(S)
Each call to `ref' creates a new cell.
| 2) isn't
|
| map!(f: S -> S, s: %) == -- from HOAGG
| map!(f, deref s)$List(S)
| s
Because
|
| assuming that map! stores its result in s? I'm not sure whether this is
ok:
|
| pro: the documentation says:
|
| map!(f,u) destructively replaces each element x of u by \axiom{f(x)}.
|
| which could be interpreted as "map! stores its result in s"
|
| con: it might well be possible to have an implementation where this is
| undesirable, i.e, although one which is destructive to s, but where s
| does not contain the result of map! afterwards. If I recall
correctly,
| sort! works that way:
|
| (14) -> l := [1,16,81,1]
|
| (14) [1,16,81,1]
| Type: List PositiveInteger
| (15) -> sort! l
|
| (15) [1,1,16,81]
| Type: List PositiveInteger
| (16) -> l
|
| (16) [1,16,81]
| Type: List PositiveInteger
|
|
| comments?
I suspect it depends on the intepretation of `in-place' update.
Which is the most common interpretation in the current
implementations.
-- Gaby
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