If statement is always false in c++ - c++

Question

I'm working my way thought Bjarne Stroustrup Programming Principles and Practice (4.64 Drill #6) and for some reason I can't get "if" to be true.
I've initialized my variables to -1000.
I can't initialize to null.
I've tried just declaring them
I've tried changing the order of my variables.
The problems I've found on stack overflow my code is much different than theirs.
I've currently added a vector which I wasn't using prior.
double val1 = 0; // initialized
double smaller; // initialized
double larger = 0; // initialized
vector<double> compare; // empty vector of doubles
int main ()
{
cout << "Please input a value, us | to stop\n"; // put into
while (cin >> val1) // cin "get from"
{
compare.push_back(val1);
if (val1 < smaller)
{
smaller = val1; // assignment giving a variable a new value
cout << val1 << " is the smallest so far \n" ;
compare.push_back(smaller);
}
else if (val1 > larger)
{
larger = val1; // assignment giving a variable a new value
cout << val1 << " is the largest so far \n";
compare.push_back(larger);
}
else
{
cout << val1 << " error\n";
}
}
}
I can't get smaller "is the smallest so far to print.
I'm teaching myself so any input would be greatly appreciated if anything in my code isn't correct or the best practices please let me know.
Thank You in Advance,

Answer 1

The first value enter must be both the larger and the smaller whatever that value, for that you need to initialize smaller with INFINITY (all valid values are smaller) and larger with -INFINITY (all valid values are larger) and to remove the else to have the two clauses effective for the first value, the third clause has no sense and must be removed.
Is it also useless to use global variables, I encourage you to not use global variables the more you can.
Because the same value can be enter several time perhaps you want a set rather than a vector to not save several times the same value ? However you do not use compare after ...
You write the message Please input... only one time, in that case it is more consistent to say Please input values... or replace
cout << "Please input a value, us | to stop\n"; // put into
while (cin >> val1) // cin "get from"
{
by
while (cout << "Please input a value, invalid value or EOF to stop" << endl,
cin >> val) // cin "get from"
Your code can be changed to be :
#include <iostream>
#include <vector>
#include <cmath>
using namespace std;
int main ()
{
double val;
double smaller = INFINITY; // initialized
double larger = -INFINITY; // initialized
vector<double> compare; // empty vector of doubles
cout << "Please input values, give an invalid value or EOF to stop" << endl; // put into
while (cin >> val) // cin "get from"
{
compare.push_back(val);
if (val < smaller)
{
smaller = val; // assignment giving a variable a new value
cout << val << " is the smallest so far" << endl;
compare.push_back(smaller);
}
if (val > larger)
{
larger = val; // assignment giving a variable a new value
cout << val << " is the largest so far" << endl;
compare.push_back(larger);
}
}
// do something with compare ?
return 0;
}
Execution :
pi#raspberrypi:/tmp $ ./a.out
Please input values, give an invalid value or EOF to stop
1234
1234 is the smallest so far
1234 is the largest so far
1
1 is the smallest so far
222
222222
222222 is the largest so far
-123
-123 is the smallest so far
23
45
aze
pi#raspberrypi:/tmp $

Answer 2

Initialise your variables to INFINITY.
double smaller = INFINITY;
double larger = -INFINITY;
The first value will be smaller/larger than any of those, so you don't limit their value range.
edit: As somebody in the comments pointed out, you would also have to remove the else between the smaller/larger parts, as for that first round, both would apply. As for the third case, not sure what that is meant to do.