List utilities

7.7

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Vincent Nys

This is a simple collection of list-processing functions which I have found helpful in general. Note that it should not be considered as stable.

package: list-utils

procedure
(findf-index proc lst) → (or/c #f exact-nonnegative-integer?)
proc : (-> any/c boolean?)
lst : list?

Finds the index of the first element in lst such that proc returns a non-false result.

procedure
(group-by proc lst) → list?
proc : (-> any/c any/c)
lst : list?

Splits a list lst into sublists such that all elements in a sublist have the same result for proc (based on equal?).

procedure
(all-splits-on pred lst) → (listof list?)
pred : (-> any/c boolean?)
lst : list?

Computes all possible splits of lst on a supplied predicate pred.

procedure
(subsequences lst) → (listof list?)
lst : list?

Returns a list of all nonempty subsequences of lst.

procedure
(replace-sublist lst sublst/i sublst/o) → list?
  lst : list?
  sublst/i : list?
  sublst/o : list?

Replaces the first occurrence of the sublist sublst/i in lst with sublst/o.

procedure
(frequencies lst) → hash?
lst : list?

Produces a mapping from every unique element in lst to its (absolute) frequency in lst.

procedure
(enumerate lst)
→ (listof (cons/c any/c exact-nonnegative-integer?))
lst : (listof any/c)

Links the n-th element in lst to index n, where n starts at 0.

procedure
(splice-in lst val pos) → list?
  lst : list?
  val : any/c
  pos : exact-nonnegative-integer?

Inserts val at position pos of lst, shifting the element that originally occupied pos (if any) one position to the right.

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