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(***********************************************************************)
(* *)
(* Objective Caml *)
(* *)
(* Pierre Weis, projet Cristal, INRIA Rocquencourt *)
(* *)
(* Copyright 2001 Institut National de Recherche en Informatique et *)
(* en Automatique. All rights reserved. This file is distributed *)
(* only by permission. *)
(* *)
(***********************************************************************)
(* Find the first occurrence of string [p] (the so-called ``pattern'')
into the string [s].
Naive algorithm. *)
let find_sub_string p s =
let plen = String.length p in
if plen = 0 then 0 else
let slen = String.length s in
if slen = 0 then raise Not_found else
let rec find c i =
if i >= slen then raise Not_found else
if s.[i] = c then find_rest c 1 (i + 1) else find c (i + 1)
and find_rest c j i =
if j >= plen then (i - plen) else
if i >= slen then raise Not_found else
if p.[j] = s.[i] then find_rest c (j + 1) (i + 1) else
find c (i + 1 - j) in
find p.[0] 0;;
let find_pat p s =
try
let i = find_sub_string p s in
print_string "Match found at character ";
print_int i;
print_newline ();
exit 0
with Not_found ->
print_string "Pattern ";
print_string p;
print_string " does not match string ";
print_string s;
print_newline ();
exit 2;;
let usage () =
print_string
"Usage: strstr2 <pat> <str>\n\
returns the index of the first occurrence of <pat> in string <str>\n";
exit 2;;
let main () =
let args = Sys.argv in
if Array.length args < 2 then usage () else
let p = Sys.argv.(1)
and s = Sys.argv.(2) in
find_pat p s;;
if !Sys.interactive then () else main ();;
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