C++ Set Precision

Precision is an important aspect of programming. Without it, your code can be inaccurate and lead to errors. In this blog post, we will explore the basics of precision and how you can use it to improve your code. From variable types to looping and string handling, you’ll learn how to keep your programs as accurate as possible. By doing so, you’ll reduce the chances of producing buggy code that causes issues in the future.

What is a precision setting in C++?

The precision setting for a C++ variable is the number of digits that will be used to represent the value of the variable. The higher the precision, the more decimal places will be used to store the value. The default precision for C++ is 6 decimal places. You can change the precision for a variable by using the precondition operator or the postcondition operator.

How to set precision in C++?

Precision is the number of digits after the decimal point in a number. In C++, you can set the precision using the typeid variable. The typeid variable can be used to store a value that uniquely identifies a particular type. For example, to set the precision for int values to 6 digits, you can use this code:

int myInt = 42;

typeid(myInt).precision = 6;

There are other ways to set precision in C++ as well. For instance, you can use the auto keyword to specify that the compiler should determine the precision for you.

How to use the std::set_precision() function?

The std::set_precision() function can be used to set the precision for a stream of data. This function can be used to specify the number of digits that will be used when representing floating-point numbers. The default precision is 6, which means that the number will be represented with six digits after the decimal point. You can use this function to change the precision for a stream of data. If you want to output data with more or fewer digits, you’ll need to use another function to format the data into a desired format.

How to use the std::set_digits() function?

The std::set_digits() function provides a way to specify the number of digits that should be used when computing the value of a numeric expression. The function takes two arguments: the first specifies the minimum number of decimal places that should be used, and the second specifies the maximum number of decimal places.

For example, to compute the value 3.141592, you can use the following code:

std::set_digits(3,14); // Use three decimal places for the value
std::cout << “3.141592” << std::endl; // Print out 3.141592

What happens if you don’t set precision in your C++ code?

If you don’t specify the precision for a C++ variable, the compiler assumes you want it to have the same precision as the data type. For example, if you declare a variable int var1, and assign a value 5 to it, then the compiler will assume that you want var1 to hold at least five bytes. If later you change your mind and want var1 to store only four bytes instead of five, you’ll need to explicitly specify that you want it to have a precision of 4. If var1 had been declared with a precision of 2, then the compiler would have assumed that you only wanted var1 to store values up to two bytes in size.

What is the difference between precision and accuracy?

Precision and accuracy are two key concepts in mathematics and programming. Precision is the degree of accuracy attainable when working with numbers. Accuracy, on the other hand, is the degree to which a program or calculation produces correct results.

Both precision and accuracy are important for developers, as they need to know how accurate their code is. For example, if a developer wants to calculate the square root of two million, they would need to be precise in their calculations so that they get accurate results. If they were not precise enough, their calculations could result in inaccurate results.

Another factor to consider when calculating precision and accuracy is the scale of the number being used. For example, if a developer is using decimals to calculate values, they will need to be more precise than if they were using whole numbers. This is because whole numbers can be represented by a smaller number of digits (e.g., 2 can be represented by 3), while decimals can only be represented by whole numbers (e.g., 2 can’t be represented by 1).

Overall, precision and accuracy are crucial concepts for developers working with numbers and mathematical operations. They need to ensure that their calculations produce accurate results so that their programs run smoothly and without errors.

How to set precision and accuracy in C++?

In C++, precision and accuracy can be set for a variable by specifying the type of data it holds. For example, if a variable stores integers, you can specify its precision as an integer. This determines how many decimal places the variable will store.

You can also specify the accuracy of a variable as a floating-point number. This determines how close to the true value the variable will represent.

When you create a variable, you typically do not have to specify its precision or accuracy. C++ automatically sets these properties for variables that are declared with the int or float data types. However, it is sometimes useful to override these defaults. For example, if you want to store real numbers in your variables instead of integers or floating-point numbers, you must explicitly set their precision and accuracy .
To set the precision and accuracy for a variable:

  1. Declare the variable using the int or float data type.
  2.  Specify the required Precision and Accuracy values in parentheses after the data type declaration .
  3.  If desired, append a sign ( + or – ) after either Precision or Accuracy value to indicate that it should be interpreted as an ordinal (positive or negative) rather than an absolute value .
  4.  The values 0 (zero) through 9 indicate positive decimal digits , while values 10 through 19 indicate positive hexadecimal digits . Values 20 through 29 indicate negative decimal digits , while values 30 through 39 indicate negative hexadecimal digits .
  5.  To specify that a variable should use the default Precision and Accuracy values for the data type, omit the parentheses and write just the data type.
    For example, the following code declares a variable named myInt with an int data type and specifies that it has a precision of 3 and an accuracy of 5:
    int myInt;
    myInt = 3; // sets precision to 3 and accuracy to 5
    myInt = 5; // sets precision to 5 and accuracy to 0 (zero)

How to get the best performance from your code?

Precision can be a huge performance win for C++ code. Here are four tips to improve your code’s performance and get the best out of its hardware:

  1. Use std::precision::traits for accurate integer calculations.

    std::precision is a handy type traits library that lets you control the precision of your integers. This can be crucial if you’re performing mathematical operations on large numbers, as each additional bit of precision can make a big difference.

  2.  Use float instead of double when possible.

    Double is a memory-intensive type, meaning that it requires more memory to store and process than float . This can lead to significant performance benefits in certain cases, especially if your application uses a lot of floating-point operations.

  3.  Use vector<> instead of direct arrays whenever possible.

    Direct arrays are simple data structures that allow you to access individual elements directly without any overhead incurred by the library or processor pipeline (i.e., it’s faster). However, using vector<> can often give you improved performance due to its optimized algorithms and memory management features.


C++ is a powerful programming language that can be used for a variety of applications. This set of articles provides insights into how to use C++ to set precision and review code. By understanding these concepts, you will be able to improve the readability and quality of your codebase.