How to convert an int64 to int in Go?

Question

In Go, what is the best strategy for converting int64 to int? I am having difficulty comparing the two

package main   import (     "math"     "strings"     "strconv" )  type largestPrimeFactor struct {     N      int     Result int }  func main() {     base := largestPrimeFactor{N:13195}     max := math.Sqrt(float64(base.N))      maxStr := strconv.FormatFloat(max, 'E', 'G', 64)     maxShift := strings.Split(maxStr, ".")[0]     maxInt, err := strconv.ParseInt(maxShift, 10, 64)      if (err != nil) {         panic(err)     } 

on this next line

    for a := 2; a < maxInt; a++ {         if isPrime(a) {             if base.N % a == 0 {                 base.Result = a             }         }     }      println(base) }  func isPrime(n int) bool {     flag := false      max := math.Sqrt(float64(n))      maxStr := strconv.FormatFloat(max, 'E', 'G', 64)     maxShift := strings.Split(maxStr, ".")[0]     maxInt, err := strconv.ParseInt(maxShift, 10, 64)      if (err != nil) {         panic(err)     }      for a := 2; a < maxInt; a++ {         if (n % a == 0) {             flag := true         }     }     return flag } 

Answer 1

You convert them with a type "conversion"

var a int var b int64 int64(a) < b 

When comparing values, you always want to convert the smaller type to the larger. Converting the other way will possibly truncate the value:

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 

Or in your case to convert the maxInt int64 value to an int, you could use

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

which would fail to execute correctly if maxInt overflows the max value of the int type on your system.