rashmi agar
56 posts
Mar 16, 2025
9:43 PM
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I am working on c++ round down project where I need to round down floating-point numbers to the nearest integer. I came across floor(), but I’m not sure if it’s the best approach. I also noticed trunc(), which seems similar. Could someone clarify the difference?
For example:
cpp
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#include
#include
int main() {
double num1 = 3.7;
double num2 = -3.7;
std::cout << "floor(3.7) = " << floor(num1) << std::endl;
std::cout << "floor(-3.7) = " << floor(num2) << std::endl;
return 0;
}
Expected Output:
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floor(3.7) = 3
floor(-3.7) = -4
So, floor() rounds down toward negative infinity. But what if I want a function that just removes the decimal part without rounding down negative numbers? Would trunc() be better?
I also read about type casting ((int)num) or using static_cast(num), but they seem to behave differently for negative numbers. What’s the best practice for rounding down in C++?
Thanks in advance!
Title: What is NaN in C++ and How to Handle It?
Forum Post:
Hey everyone,
I’m encountering some strange behavior in my C++ program related to NaN (Not a Number). I learned that NaN can appear when performing undefined operations like:
cpp
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#include
#include
int main() {
double a = 0.0;
double result = sqrt(-1); // Produces NaN
double div = a / a; // Also produces NaN
std::cout << "sqrt(-1): " << result << std::endl;
std::cout << "0/0: " << div << std::endl;
return 0;
}
I was wondering:
How can I check if a value is NaN?
What’s the best way to handle NaN values in calculations?
Are there cases where NaN can silently propagate through calculations?
From my research, it looks like std::isnan() can be used to check for NaN, but I’m not sure if there are any caveats I should be aware of. Also, why does NaN == NaN return false?
Would love to hear best practices on detecting and handling NaN in real-world C++ applications.
Thanks!
Title: How to Perform Modulus Operation on Floating-Point Numbers in C++?
Forum Post:
Hi all,
I need to calculate the modulus (remainder) of two floating-point numbers in C++. I know that for integers, the modulus operator % works fine, but it doesn’t seem to work with float or double.
I found fmod() in , and it seems to work:
cpp
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#include
#include
int main() {
double a = 5.5;
double b = 2.0;
std::cout << "fmod(5.5, 2.0) = " << fmod(a, b) << std::endl;
return 0;
}
Output:
cpp
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fmod(5.5, 2.0) = 1.5
I also came across remainder(), which gives a different result:
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std::cout << "remainder(5.5, 2.0) = " << remainder(a, b) << std::endl;
Output:
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remainder(5.5, 2.0) = -0.5
This confused me because fmod() and remainder() don’t behave the same way. Can someone explain the difference between them?
Also, is there any way to implement a custom floating-point modulus function that mimics the integer % behavior?
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