String to double conversion without sstream or boost lexical cast - c++

Question

Hey guys I have a question about my code. Here's what we have to do:
"Ask the user to read a file. The file will be in the same format as “items.txt” on the website. There will
always be a list of items with a name and price followed by some amount of recipes. If a recipe for an
item is not present, the only way to make the item is to buy it directly. Make a program that reads all
the items and recipes, then says how much profit can be made by making each item.
If an item has no recipe, you would buy that item then resell it for the same price and make a profit of
0. If an item does have a recipe, you would buy the materials to make this item and subtract this cost
from the price of the final product.
There will only be zero or one recipe per item. The items will always be listed first. The names of
items will always be a single word (using a _ to join names that are normally multiple words). You
may assume there will be less than 50 items and each recipe will use less than 50 other items to create a
final product."
This is the items1.txt we use
Item: Wood 2.5
Item: Metal 5.5
Item: Cat 900
Item: Spear 50.7
Recipe: Spear = Wood + Wood + Metal ;
I have what I think would work but I can't get a certain line to work. I'm trying to use stod but apparently my school's computers don't support it. I also tried boost lexical cast and that wouldn't work either.
It says "stod: was not declared in this scope.
Here's my code:
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <string>
#include <algorithm>
#include <sstream>
using namespace std;
string nextstring(string str, int start_index);
int split(string str, string a[], int max_size);
int main()
{
ifstream in_stream;
string fileName;
cout << "Enter the file name : ";
cin >> fileName;
in_stream.open(fileName.c_str());
//error checking
if (in_stream.fail())
{
cout << "File could not be opened." << endl;
exit(1);
}
string items[50];
double items_value[50];
string recipe[50];
string rname = recipe[0];
double profit = 0;
int j = 0;
string lines;
int number_of_lines = 0;
while(getline(in_stream, lines))
{
if(lines.substr(0,5) == "Item:")
{
int beginning = lines.find_first_of(' ') + 1;
int next_space = lines.find(" ", beginning);
items_value[j] = stod(lines.substr(next_space));
items[j] = lines.substr(beginning,lines.find_first_of(' ', beginning) - beginning);
j++;
}
if(lines.substr(0,7) == "Recipe:")
{
int max_size = lines.length();
int cnt = split(lines,recipe,max_size);
double profit1 = 0;
double profit2 = 0;
for(int j = 3; j < cnt; j++)
{
for(int i = 0; i < 4; i++)
{
if((recipe[j] == items[i]) && (recipe[j] != "+")&& (recipe[j] != ";"))
{
cout << "Making " << items[i] << ", " << "profit = 0" << endl;
profit1 += items_value[i];
}
if(recipe[1] != items[i])
{
profit2 = 0;
}
}
}
for(int i = 0; i < cnt; i++)
{
if((recipe[1] == items[i]))
{
profit = items_value[i];
cout << "Making " << items[i] << ", " << "profit = ";
}
}
cout << profit - profit1 << endl;
}
}
in_stream.close();
return 0;
}
string nextstring(string str, int start_index)
{
int y =0;
y = str.find(' ',start_index);
y = y-start_index;
str = str.substr(start_index,y);
return str;
}
int split(string str, string a[], int max_size)
{
int i;
int num = 0;
for (i=0; i<max_size; i++)
{
a[i] = nextstring(str,num);
num = num + a[i].length() + 1;
if(num >= str.length())
{
i++;
break;
}
}
return i;
}

Answer 1

First step is get a decent compiler from this century ;) stod has been available since c++11, which really means that it was available probably a few years before that.
If stod isn't available to you then you can revert to the cstdlib function atof.