Exer17_33.cpp

// Note: this file uses data file ./data/map and ./data/input
#include <cstddef>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>
#include <map>
#include <random>
#include <ctime>
#include <stdexcept>
using std::size_t;
using std::cout;
using std::endl;
using std::ifstream;
using std::istringstream;
using std::string;
using std::vector;
using std::map;
using std::default_random_engine;
using std::uniform_real_distribution;
using std::runtime_error;
map<string, vector<string>> buildMap(ifstream &map_file)
{
    map<string, vector<string>> trans_map;
    string key, value;
    while(map_file >> key && getline(map_file, value))
    {
        if(value.size() > 1) {
            string word;
            istringstream is(value);
            while(is >> word)
            trans_map[key].push_back(word); // using white space as separator
        }
        else
            throw runtime_error("no rule for " + key + " at " + __func__);
    }
    return trans_map;
}
const string& transform(const string &s, const map<string, vector<string>> &m)
{
    // static object to generate random numbers
    static default_random_engine e(time(0));
    static uniform_real_distribution<double> u(0, 1);
    auto map_it = m.find(s);
    if(map_it != m.cend()) {
        size_t select = map_it->second.size() * u(e); // truncated, won't be out of range
        return map_it->second[select];
    }
    else
        return s;
}
void word_transform(ifstream &map_file, ifstream &input)
{
    auto trans_map = buildMap(map_file);
    string text;
    while(getline(input, text))
    {
        istringstream stream(text);
        string word;
        bool firstword = true;
        while(stream >> word)
        {
            // process leading space
            if(firstword)
                firstword = false;
            else
                cout << " ";
            // process word
            cout << transform(word, trans_map);
        }
        cout << endl;
    }
}
int main(int argc, char *argv[])
{
    if(argc != 3)
        return -1;
    for (size_t i = 0; i < 10; ++i) {
        ifstream map_file(argv[1]), input_file(argv[2]);
        try
        {
            word_transform(map_file, input_file);
        }
        catch(runtime_error err)
        {
            cout << "Error: " << err.what() << endl;
        }
    }
    return 0;
}