Negating problems

[gold]

I read the part about the negate function on this website and since most of it i don't understand how to read i need a little help understanding what's wrong with my code.

if (b1 > b2){
   b3 = b1 - b2;
   transform ( b3, b3+1, b3, negate<int>() );}
if (b2 > b1){
   b3 + b2 - b1;}

As you can see it finds the difference in two numbers and shows you the loss/gain kinda (in my project here)....

I run windows with Mingw compiler and it really doesn't like that line.

Help would be much appreciated.

[ModShop]

negate? Thats not a standard function... Why do you need it? Do you have the library its in?

[gold]

It's doesn't have a library as it seems and its part of the operator class in functional... its here in this website's reference: http://www.cplusplus.com/reference/std/functional/negate/

And i would need it just to make a number negative, its such a simple process... so do you know any other ways....

[ModShop]

Yes, very simple. But first, the reason why negate isn't working is because you aren't putting any number into the ().

negate<int>(15);

Simple negation:

int makeNegative(int num)
{
    if (num>0)
    num *= -1;

    return num;
}

[Intrexa]

So, you mean like taking 5, and turning it into -5?

Multiply by -1

Edit: if you need to gurentee it is negative, check to make sure it is positive before multiplying by -1

[gold]

Thank you very much i do feel like an idiot not remembering how to do that lol..... thanks anyways!

[DSLq5Di1]

@gold
I think your confusion stems from trying to use a function object (std::negate) for a single value, rather than in an algorithm on a range of values as it is designed for. http://www.cplusplus.com/reference/algorithm/

As for negating a single value, its as simple as placing a minus sign before it.

inline int Negate(int n)
{
    return -n;
}