//
// example of recursion:
//   function to perform search-and-replace on list of strings,
//   plus main program illustrating its use.
//
// input:  none.
// output:  result of calling function on a predefined input.
//

#include <string>
#include <iostream>
#include <cstdlib>
#include "seq.h"        // Note the "", not <>, causes this
                        // directory to be searched as well as the
                        // standard places implied by <>.
using namespace std;

// Given a list of strings, return a (new) list with one string
//   substituted for the other string.
// Post:  returns a list of strings that consists of SL with
//   all occurrences of oldString replaced by newString.
Seq<string> subst(const string & oldString, const string & newString,
                  const Seq<string> & SL) {
  if (SL.empty())
    return SL;
  else {
    if (SL.hd() == oldString)
      return Seq<string>(newString, subst(oldString, newString, SL.tl()));
    else
      return Seq<string>(SL.hd(), subst(oldString, newString, SL.tl()));
  }
}

// Print contents of a list of strings.
// Post:  all elements of SL printed to standard output, one per line.
void print(const Seq<string> & SL) {
  if (!SL.empty()) {
    cout << SL.hd() << endl;
    print(SL.tl());
  }
}

// Test program.
int main(void) {
  Seq<string> testString = 
    Seq<string>("ab", Seq<string>("cd", Seq<string>("ab", 
                Seq<string>("ef", Seq<string>()))));
  print(subst("ab", "AB", testString));
  return EXIT_SUCCESS;
}