Module String.Search_pattern

Substring search and replace functions. They use the Knuth-Morris-Pratt algorithm (KMP) under the hood.

The functions in the Search_pattern module allow the program to preprocess the searched pattern once and then use it many times without further allocations.

type t
val sexp_of_t : t -> Sexp.t
val create : string -> t

create pattern preprocesses pattern as per KMP, building an int array of length length pattern. All inputs are valid.

val matches : t -> string -> bool

matches pat str returns true if str matches pat

val index : ?⁠pos:int -> t -> in_:string -> int option

pos < 0 or pos >= length string result in no match (hence index returns None and index_exn raises).

val index_exn : ?⁠pos:int -> t -> in_:string -> int
val index_all : t -> may_overlap:bool -> in_:string -> int list

may_overlap determines whether after a successful match, index_all should start looking for another one at the very next position (~may_overlap:true), or jump to the end of that match and continue from there (~may_overlap:false), e.g.:

  • index_all (create "aaa") ~may_overlap:false ~in_:"aaaaBaaaaaa" = [0; 5; 8]
  • index_all (create "aaa") ~may_overlap:true ~in_:"aaaaBaaaaaa" = [0; 1; 5; 6; 7; 8]

E.g., replace_all internally calls index_all ~may_overlap:false.

val replace_first : ?⁠pos:int -> t -> in_:string -> with_:string -> string

Note that the result of replace_all pattern ~in_:text ~with_:r may still contain pattern, e.g.,

replace_all (create "bc") ~in_:"aabbcc" ~with_:"cb" = "aabcbc"
val replace_all : t -> in_:string -> with_:string -> string