Why don't we have a composition operator in Pervasives?

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I did some tests and it seems that with flamba the equivalence between the two idioms is restored. I tested with this functions:

let f x = 
  ignore (Array.create ~len:50 x);
  fun y -> x + y

let f_staged x =
  ignore (Array.create ~len:50 x);
  Staged.stage (fun y -> x + y)

let g x y = x + y

let h x y = x * y

I composed or piped f or g with h and got this results:

  Name                 Time/Run   mWd/Run   Percentage  
 -------------------- ---------- --------- ------------ 
  f composed             3.20ns                  3.51%  
  f with pipe           91.09ns    51.00w      100.00%  
  g composed             3.19ns                  3.50%  
  g with pipe            3.17ns                  3.48%  
  compose with stage     3.19ns                  3.50%  
  pipe with stage        3.18ns                  3.49%

The pipe idiom works well only with functions of the form fun x y -> ... but if we do some heavy computation with x before defining fun y -> ... then we have to stage the result or use the composition idiom.

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