Convert a float64 to an int in Go

Question

How does one convert a float64 to an int in Go  I know the strconv package can be used to convert anything to or from a string  but not between data types where one isn t a string  I know I can use fmt Sprintf to convert anything to a string  and then strconv it to the data type I need  but this extra conversion seems a bit clumsy - is there a better way to do this

User · Accepted Answer

package main import  fmt  func main       var x float64   5 7   var y int   int x    fmt Println y      outputs  5

User · Answer

You can use int   function to convert float64 type data to an int  Similarly you can use float64    Example   func check n int  bool           count the number of digits      var l int   countDigit n      var dup int   n      var sum int   0          calculates the sum of digits         raised to power      for dup  gt  0              sum    int math Pow float64 dup   10   float64 l               dup    10              return n    sum

User · Answer

If its simply from float64 to int  this should work  package main  import        fmt     func main         nf      float64 -1 9999  -2 0001  -2 0  0  1 9999  2 0001  2 0         round     fmt Printf  Round          for    f    range nf           fmt Printf   d    round f             fmt Printf   n          rounddown ie  math floor     fmt Printf  RoundD         for    f    range nf           fmt Printf   d    roundD f             fmt Printf   n          roundup ie  math ceil     fmt Printf  RoundU         for    f    range nf           fmt Printf   d    roundU f              fmt Printf   n       func roundU val float64  int       if val  gt  0   return int val 1 0        return int val     func roundD val float64  int       if val  lt  0   return int val-1 0        return int val     func round val float64  int       if val  lt  0   return int val-0 5        return int val 0 5      Outputs   Round   -2 -2 -2 0 2 2 2  RoundD  -2 -3 -3 0 1 2 2  RoundU  -1 -2 -2 0 2 3 3    Here s the code in the playground - https   play golang org p HmFfM6Grqh

User · Answer

Correct rounding is likely desired    Therefore math Round   is your quick    friend  Approaches with fmt Sprintf and strconv Atois   were 2 orders of magnitude slower according to my tests with a matrix of float64 values that were intended to become correctly rounded int values   package main import        fmt       math    func main         var x float64   5 51     var y float64   5 50     var z float64   5 49     fmt Println int math Round x        outputs  6      fmt Println int math Round y        outputs  6      fmt Println int math Round z        outputs  5      math Round   does return a float64 value but with int   applied afterwards  I couldn t find any mismatches so far

User · Answer

Simply casting to an int truncates the float  which if your system internally represent 2 0 as 1 9999999999  you will not get what you expect   The various printf conversions deal with this and properly round the number when converting   So to get a more accurate value  the conversion is even more complicated than you might first expect   package main  import        fmt       strconv     func main         floats      float64 1 9999  2 0001  2 0      for    f    range floats           t    int f          s    fmt Sprintf    0f   f          if i  err    strconv Atoi s   err    nil               fmt Println f  t  i            else               fmt Println f  t  err                      Code on Go Playground

[go] Convert a float64 to an int in Go

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