How to assign a float with two digits after decimal point to another float in c++

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First of all, I don't want to print my float. So printf("%.2f", x) doesn't work for me. I have already checked setprecision(), and it doesn't work for me.

Here is my code

#include <iostream>
using namespace std;
int main()
{
    float obtained = 256.714964;
    float usable = 256.71; // I want to make obtained float with two digits 
                           // after decimal point without any round.
}

Instead of a float, you could use a ratio. Do all your computations with std::centi (1/100ths).

How to print a float with two decimal places in Python, How do you print float up to 2 decimal places? Floating points aren't represented with decimal digits so no, you absolutely cannot have a float with just two decimal digits. The only options you have is to print the float with just two decimal digits, or to use a data type who represents real numbers with decimal digits. – bolov Oct 19 '18 at 22:13

Based on comments you seem to have a difficult time understanding why you cannot have a float with two (or any number) of digital digits.

Please bear with me and let's make an exercise. Let's create our own data type on 3 bits who represents real numbers in the interval [0, 50). Lets call it my_type. Because we have only 3 bits there can only be 8 values representable by our my_type. We want to have values distributed evenly across the interval. So we chose to go in 50 / 8 = 6.25 increments across the interval.

This is what we get:

Internal representation  |  Represented Value (real number)
                 (bits)  |
-------------------------+--------------------------
                     000 |  0
                     001 |  6.25
                     010 | 12.5
                     011 | 18.75
                     100 | 25
                     101 | 31.25
                     110 | 37.5
                     111 | 43.75

That's our data type. Only those 8 numbers are representable. When we assign a number to a my_type the variable will get the closest representable number. So, for instance:

my_type a1 = 10;      // a1 is 12.5
my_type a2 = 31.1471; // a2 is 31.25
my_type a3 = 25.789;  // a3 is 25
my_type a4 = 29.89;   // a4 is 31.25

Now you say: I have the number 12.67893 and I want to store in a my_type variable the number with just 2 digits. You can't. You simply can't. The closest value you can have is 12.5. Let's generalize. You say I have a number with a value in the interval [0, 50). I want to store it in a my_type variable with just two decimals. You can't. Because the internal representation of my_type doesn't deal with decimal digits. Some values have no decimal digits, some have 1 decimal digit and some have two. The only thing you can do is to print the my_type with two digits.

The story with float is a lot more complicated. The numbers are stored in base 2 and there are well defined rules. Some numbers represented by float have an infinite number of decimal digits. Some decimal numbers are not representable by float and the closes representable is chosen. It's true that float has a greater precision than our my_type, but the principle is the same.

If you try to represent a number with two decimal digits in a float you might find that that number is not representable in float and the closest representation is chosen. For instance instead of x.75 you might store a number that actually is something like x.7499999999999 or x.7500002387. For large numbers the precision lost is even before the dot so instead of 16'777'217.0f you might store something like 16'777'216.0f.

What is the meaning of .1f ,.2f in c?, , without rounding it off. like: a = 91.827345; printf("%. 2f", a); The float () function allows the user to convert a given value into a floating-point number. In this tutorial, you will learn how to convert a number into a floating-point number having a specific number of decimal points in Python programming language. In the above code, the given the float () is a built-in function having a single parameter

#include <cmath>

float two_decimal_places(float f) {
    return std::floor(f * 100.0) / 100.0;
}

Java: Floating Point Numbers, How do you print a float with 2 decimals in Python? The short answer is : use the Python round() to change to 2 decimal places. The two decimal places are the two digits after the decimal point in a float variable. You can also round float to 3 decimal places after the decimal point. The round() is the commonly known function of Python to perform this task.

It sounds like you need to learn about the difference between a floating point value and its representation as characters. You have little control over the precision of the value until you print it out.

) places after the decimal point, with no restriction on the number places to the left of the decimal point. In C, there is a format specifier in C. To print 4 digits after dot, we can use 0.4f in printf (). Below is program to demonstrate the same. // C program to set precision in floating point numbers. // using format specifier. #include<stdio.h> float num = 5.48958123; // 4 digits after the decimal point. printf("%0.4f", num);

int(avg * 100) / 100.0f Thats the logic.

of precision. The single precision number format occupies 4 bytes, or 32 bits, in computer memory, while the double precision number format occupies 8 bytes, or 64 bits, in the memory of a computer. In this output the number of digits after decimal are 6, which is default format of float value printing. Now, we want to print 2 digits only after decimal. Use "%.nf" format specifier. By using this format specifier we can print specific number of digits after the decimal, here "n" is the number of digits after decimal point.

Notice that there are three different rounding rules you might want to choose: round down (ie, truncate As several others have pointed out, due to the quirks of floating point fixed; ss.precision(decDigits); // set # places after decimal ss << x; return ss.str(); } In C++ (or in C with C-style casts), you could create the function: @VilasJoshi, setprecision set the number of digits after the decimal, if there are 5 digits and we use setprecision(2) we will get 2 digits , but if there are 0 digits it will show none, using fixed we fix that much digits have to be shown so 5 will be represented as 5.00 no 5 – vaibnak Oct 18 '18 at 13:33

C program to set precision in floating point numbers In C, there is a format specifier in C. To print 4 digits after dot, we can use 0.4f in printf(). See your article appearing on the GeeksforGeeks main page and help other Geeks. Rounding Floating Point Number To two Decimal Places in C and C++ · Format specifiers in  The "%.2f" passed to the format method indicates we wish to use two decimal places in the conversion. If the float contains more decimal digits like in the example, it is expected that the result will be rounded. Hence the output should be: 888.79

Rounding Floating Point Number To two Decimal Places in C and C++ First Method:- Using Float precision. Second Method : Using integer typecast If we are in Function then how return two decimal point value. Third Method : using sprintf() and sscanf() [code]#include<stdio.h> int main() { float x=65.500000; printf("%.2f",x); } [/code]

Comments
  • I guess you could do something like multiply 100, cast to int, and then divide by 100.0, but are you sure that's what you want?
  • Floats don't have digits. Only their string representation does. You need a fixed- place representation to have any guarantees, like represent that as 25671 with the understanding that there's a decimal in there.
  • No, I am calculating the average values of some datafiles. At the end, I will print them but in order to show it I need to pass the value with a parameter which has two digits after decimal point.
  • Why not do all your calculations with the highly-accurate values? You can still truncate decimal places when you output them, and that'll avoid accumulating errors.
  • @James you seem stubborn to understand that that's not how floating points work. Floating points aren't represented with decimal digits so no, you absolutely cannot have a float with just two decimal digits. The only options you have is to print the float with just two decimal digits, or to use a data type who represents real numbers with decimal digits.
  • In the comment box avoid say "thanks" but how possible I don't say thanks? Thank you a lot.
  • @James you are welcome. You upvote the answer if it helped you.
  • This could turn 256.71 into something like 256.709999999483021.
  • Well, yeah. That's how floats work.
  • That's why this code is only sorta kinda close to a solution.
  • In the way I want to use, it doesn't matter how floats work or what they do. I want to show just two digits after decimal point and that's all.
  • @James In your question you say, "I don't want to print my float" but no you say " I want to show just two digits after decimal point and that's all". These two statements appear to contradict each other. Which is it?
  • That's more logical.
  • @James So the solution is to use printf() and it's formatting flags when you are ready to display the number.