How Can I Safely Convert int64 to int in Go?

Efficient Conversion of int64 to int in Go

When dealing with different data types in Go, particularly when comparing values, it often becomes necessary to convert between types. One common scenario is the conversion from int64 to int. This article provides the best approach for such conversions, highlighting potential pitfalls.

Conversion Strategy

The process of converting an int64 to int in Go is straightforward. To perform the conversion, simply use a type conversion expression:

var a int
var b int64

int64(a) < b

When comparing values of different types, it is essential to convert the smaller type to the larger type. Converting in the other direction may result in data truncation and incorrect comparisons.

Comparison Example

Consider the following Go code:

var x int32 = 0
var y int64 = math.MaxInt32 + 1 // y == 2147483648

if x < int32(y) {
    // this evaluates to false, because int32(y) is -2147483648
}

In this case, attempting to compare x to int32(y) will result in an incorrect evaluation because int32(y) truncates the actual value of y and effectively changes it to -2147483648. To avoid such issues, it is always advisable to convert the smaller type to the larger type.

Practical Application

In your specific code example, converting maxInt to an int would require the following adjustment:

for a := 2; a < int(maxInt); a++ {

This modification ensures that the comparison is performed correctly. However, it is important to note that if maxInt exceeds the maximum value of the int type on your system, the conversion may fail. To mitigate this risk, consider using a larger data type, such as int64, for maxInt to prevent potential overflow.

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