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Feature request #3715

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vicuna opened this issue Jul 5, 2005 · 2 comments
Closed

Feature request #3715

vicuna opened this issue Jul 5, 2005 · 2 comments
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feature-wish wontfix

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@vicuna
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vicuna commented Jul 5, 2005

Original bug ID: 3715
Reporter: administrator
Status: closed
Resolution: won't fix
Priority: normal
Severity: feature
Category: ~DO NOT USE (was: OCaml general)

Bug description

I looked all through the standard list library for a function like
this and couldn't find it, but it should definately be in there.

let rec apply n list =
match list with
[] -> []
| h::t -> (h n) :: (apply n t);;
val apply : 'a -> ('a -> 'b) list -> 'b list =

or tail recursively...

let rec apply n list res =
match list with
[] -> res
| h::t -> (apply n t) ((h n) :: res);;
val apply : 'a -> ('a -> 'b) list -> 'b list =

@vicuna
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vicuna commented Jul 8, 2005

Comment author: administrator

I looked all through the standard list library for a function like
this and couldn't find it, but it should definately be in there.

let rec apply n list =
match list with
[] -> []
| h::t -> (h n) :: (apply n t);;
val apply : 'a -> ('a -> 'b) list -> 'b list =

It's not in the standard library because:

  1. It is not often needed.
  2. It's a one-liner:

let apply n list = List.map (fun f -> f n) list;;

BTW, your tail-recursive version is broken.

-- Damien

@vicuna
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vicuna commented Jul 8, 2005

Comment author: administrator

wish denied DD 2005-07-08

@vicuna vicuna closed this as completed Jul 8, 2005
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@vicuna