C programming (rounding up)

Greenmachine

Hey guys just want a little help with a problem I am having regard round a value up. It is a perimeter fencing problem. User inputs diameter of a circular field.
User inputs the length of each roll
User inputs the cost of each roll
pi given as 3.1416
What has work
user inputs
Calculation of circumference of field
Number of roll required returns a value with decimal(need this to be rounded up)
cost of fencing field above value * cost per roll a user input.

using <math.h> library anything here I can use I don't want to use int here because it will round down value where the decimal value is less than 0.5 underestimating the true cost.

maki

The ceil function of math.h is what you want to use.
ceil(your float here) will round it up.

stefanovich

Greenmachine wrote: »

Hey guys just want a little help with a problem I am having regard round a value up. It is a perimeter fencing problem. User inputs diameter of a circular field.
User inputs the length of each roll
User inputs the cost of each roll
pi given as 3.1416
What has work
user inputs
Calculation of circumference of field
Number of roll required returns a value with decimal(need this to be rounded up)
cost of fencing field above value * cost per roll a user input.

using <math.h> library anything here I can use I don't want to use int here because it will round down value where the decimal value is less than 0.5 underestimating the true cost.

Use a float or a double.

Greenmachine

maki wrote: »

The ceil function of math.h is what you want to use.
ceil(your float here) will round it up.

Okay will give that a try so perform original calculation to achieve an answer for rolls required then something like

ceil(rr);
tc = (rr*rc); //tc total cost, rr rolls required, rc is roll cost
then my normal printf statements:

maki

Greenmachine wrote: »

Okay will give that a try so perform original calculation to achieve an answer for rolls required then something like

ceil(rr);
tc = (rr*rc); //tc total cost, rr rolls required, rc is roll cost
then my normal printf statements:

Just note that ceil(rr) won't store the value in any variable; it'll just do the calculation in memory.
You'll want something like:
float roundedResult = ceil(rr);

Greenmachine

maki wrote: »

Just note that ceil(rr) won't store the value in any variable; it'll just do the calculation in memory.
You'll want something like:
float roundedResult = ceil(rr);

Brilliant will give that a go.

PrzemoF

Side note: there should be M_PI or HALF_PI defined in math.h that you can use.

Greenmachine

PrzemoF wrote: »

Side note: there should be M_PI or HALF_PI defined in math.h that you can use.

Not come across either of those. For the question I was looking at we were given a value for pi so did not need to call a predifined value. I will have a look into these two again. When would I use HALF_PI? The trapezoid rule perhaps?

jgh_

Greenmachine wrote: »

Not come across either of those. For the question I was looking at we were given a value for pi so did not need to call a predifined value. I will have a look into these two again. When would I use HALF_PI? The trapezoid rule perhaps?

It's useful if you're doing geometric transformations and such. A handy way of getting a 90 degree angle