Shape Volume/Weight decider using functions

[VictoryCFC]

I have written this program which is testing the use of functions and aims to take in 3 inputs weight, length and diameter of a shape and validates them. Next an estimated volume is calculated by doing pie * (radius squared) * length. From this a weight is calculated using a conversion of 1mm cubed to 0.05 grams. Finally this weight is to be compared against the weight entered at the start and the shape is determined as either a wedge or a cylinder depending on whether the difference in the weights is above 0.1 grams.

However I cant get any output as errors like "6:39: error: expected identifier before numeric constant
6:39: error: expected ',' or '...' before numeric constant" are coming up.

 #include <iostream>
using namespace std;

bool isValidDimensions(double length, double diameter);
double eval_volume(double length, double diameter);
double eval_weight(double est_volume, 0.05);
void wedge_or_cylinder(double est_weight, double act_weight);

int main()
{
double length = 0; double diameter = 0; double act_weight = 0;
double est_volume = 0; double est_weight = 0;

cout << "Enter the length:"<< endl;
cin>> length;

cout << "Enter the diameter" << endl;
cin >> diameter;

cout << "Enter the actual weight:" << endl;
cin >> act_weight;

if (!isValidDimensions(length, diameter))
// check len is within the range 1mm to 20mm and dia is in range 0.1mm - 1mm
{
    cout<<"Dimensions are not valid";
}

else
{
// estimate volume
est_volume = eval_volume(length, diameter);
// estimate weight, density 0.05
est_weight = eval_weight(est_volume, 0.05);
// display if wedge or cylinder
wedge_or_cylinder(est_weight, act_weight);

cout <<"Volume is " <<est_volume << endl;
cout <<"Weight is " <<est_weight << endl;
cout <<"The shape is a " <<wedge_or_cylinder;
}

return 0;
}

bool isValidDimensions(double length, double diameter)
{
    if (length <1.00 || length >20.00)
    {
        return false;
    }
    else
    {
        return true;
    }
    
     if (diameter <0.1 || diameter >1.00)
    {
        return false;
    }
    else
    {
        return true;
    }
   
}

double eval_volume(double length, double diameter)
{
    double radius = diameter/2;
    double radius_squared = radius*radius;
    double est_volume = 3.142 * radius_squared * length;
   
    return est_volume;
}

double eval_weight(double est_volume, 0.05)
{
    double est_weight = est_volume/0.05;
    return est_weight;
}

void wedge_or_cylinder(double est_weight, double act_weight)
{
    if (est_weight > act_weight + 0.10 || est_weight < act_weight - 0.10)
    {
        cout <<"wedge";
    }
    else
    {
        cout <<"cylinder";
    }
}

[jonnin]

that says that line 6 is messed up.

6:39: error: expected identifier before numeric constant
^ line number
    ^^ line position
          ^^error complaint:  found an unexpected constant value here

and it is

double eval_weight(double est_volume, 0.05);

you can't do that.
you can do this:
double eval_weight(double est_volume); //no value needed, pass 0.05 if that is what you want when you call it?!
or this:
double eval_weight(double est_volume = 0.05); // gives est_volume a default value.

or this:
double eval_weight(double est_volume, double whatisthis = 0.05); //was it a second parameter you wanted?

but you can't just have a number in a function parameter list.

[VictoryCFC]

Okay thanks for that, Iv made a couple of changes and it almost completely works. I get all output except either "wedge" or "cylinder"?

#include <iostream>
using namespace std;

bool isValidDimensions(double length, double diameter);
double eval_volume(double length, double diameter);
double eval_weight(double est_volume);
string wedge_or_cylinder(double est_weight, double act_weight, string shape);

int main()
{
double length = 0; double diameter = 0; double act_weight = 0; double est_volume = 0; double est_weight = 0; string shape;

cout << "Enter the length:"<< endl;
cin>> length;

cout << "Enter the diameter" << endl;
cin >> diameter;

cout << "Enter the actual weight:" << endl;
cin >> act_weight;

if (!isValidDimensions(length, diameter))
// check len is within the range 1mm to 20mm and dia is in range 0.1mm - 1mm
{
    cout<<"Dimensions are not valid";
}

else
{
// estimate volume
est_volume = eval_volume(length, diameter);
// estimate weight, density 0.05
est_weight = eval_weight(est_volume);
// display if wedge or cylinder
wedge_or_cylinder(est_weight, act_weight, shape);

cout <<"Volume is " <<est_volume << " mm" << endl;
cout <<"Weight is " <<est_weight << " g" << endl;
cout <<"The shape is a " <<shape;
}

return 0;
}

bool isValidDimensions(double length, double diameter)
{
    if (length <1.00 || length >20.00)
    {
        return false;
    }
    else if (diameter <0.1 || diameter >1.00)
    {
        return false;
    }
    else
    {
        return true;
    }
   
}

double eval_volume(double length, double diameter)
{
    double radius = diameter/2;
    double radius_squared = radius*radius;
    double est_volume = 3.142 * radius_squared * length;
   
    return est_volume;
}

double eval_weight(double est_volume)
{
    double est_weight = est_volume/0.05;
    return est_weight;
}

string wedge_or_cylinder(double est_weight, double act_weight, string shape)
{
    
    if (est_weight > act_weight + 0.10 || est_weight < act_weight - 0.10)
    {
        shape = "wedge";
    }
    else
    {
        shape = "cylinder";
    }
    return shape;
}

OUTPUT:
Enter the length:
15
Enter the diameter
1
Enter the actual weight:
20
Volume is 11.7825 mm
Weight is 235.65 g
The shape is a

[jonnin]

20
Volume is 11.7825 mm
Weight is 235.65 g

that weight is more than 11 times larger than the actual. Computation problem?

maybe get rid of shape, it is not necessary or useful.

 if (est_weight > act_weight + 0.10 || est_weight < act_weight - 0.10)
    {
        return "wedge";
    }
       return "cylinder";

and in main, make a choice...
shape = wedge_or_cylinder(est_weight, act_weight, shape); //do this
OR DO THIS

cout <<"Volume is " <<est_volume << " mm" << endl;
cout <<"Weight is " <<est_weight << " g" << endl;
cout <<"The shape is a " << wedge_or_cylinder(est_weight, act_weight, shape);

OR make it passed by reference and a void function (no return statements).

shape is not modified by the function because it isnt passed by reference.
you do not use the returned value.

[VictoryCFC]

Ok got it working now, thanks man