How to Safely Convert Int64 to Int in Go?

Converting Int64 to Int in Go: A Guide

Type conversion is a common task in programming, and in Go, it's straightforward to convert between two integer types. Understanding the differences between int and int64 is crucial for accurate and efficient conversions.

The Challenge

When working with int64 (64-bit integer) and int (32-bit integer) in Go, developers may encounter the need to compare the values of these two types. However, converting int64 to int can be tricky, as direct comparison may lead to unexpected results due to overflow or underflow.

For example, a common mistake is to directly convert an int64 value to int, as shown in the provided code snippet:

for a := 2; a < maxInt; a++ {
    if isPrime(a) {
        if base.N % a == 0 {
            base.Result = a
        }
    }
}

Here, maxInt is an int64 value, and the loop condition (a < maxInt) attempts to compare an int32 (a) with an int64. This can lead to incorrect results.

The Solution

To accurately compare int64 values with int in Go, the correct approach is to convert the int type to int64. This ensures that both values are of the same type, eliminating the risk of overflow or underflow:

for a := 2; a < int64(maxInt); a++ {
    if isPrime(a) {
        if base.N % a == 0 {
            base.Result = a
        }
    }
}

By casting a to int64, the loop condition correctly compares an int64 value to another int64 value, ensuring proper comparison.

Additional Notes

When performing this type conversion, it's important to consider the potential for overflow or underflow. If the converted value is too large for the target type, it may result in an overflow, leading to an incorrect value. Conversely, if the converted value is too small, it may result in an underflow, which may truncate the value to a lower bound.

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