How to Safely Convert Int64 to Int in Go: A Guide to Avoiding Overflow and Truncation Issues

Int64 to Int Conversion in Go: Strategies and Pitfalls

When working with numeric types in Go, it's crucial to understand the subtle differences between them. One common scenario is the need to convert an int64 (a 64-bit integer) to an int (a 32-bit integer).

Type Conversion vs. Comparison

To convert int64 to int, simply perform a type conversion using the respective data type in the expression, such as:

var a int64
var b int
a = int64(b)

However, be cautious when comparing values of different types. Always convert the smaller type to the larger to avoid potential truncation. For example:

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
}

Casting Int64 to Int with Limitations

In your specific example, where you encounter the error when converting maxInt from int64 to int, consider the following:

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

This code will fail when maxInt overflows the maximum value of the int type on your system. To avoid this issue, use int64(a) < maxInt to ensure that the comparison is performed correctly.

Remember, understanding the nuances of different data types and type conversions is essential for writing robust and efficient Go code.

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