.. highlight:: go

numstats2.go
============

::

    // numstats2.go

    // To run at the command line:
    //    $ go run numstats2.go

    package main

    import (
        "bufio"
        "fmt"
        "os"
        "sort"
        "strconv"
    )

    func sum(nums []int) int {
        result := 0
        for _, n := range nums {
            result += n
        }
        return result
    }

    func mean(nums []int) float64 {
        return float64(sum(nums)) / float64(len(nums))
    }

    func min(nums []int) int {
        if len(nums) == 0 {
            panic("can't take min of empty slice")
        }

        result := nums[0]
        for _, n := range nums[1:] {
            if n < result {
                result = n
            }
        }
        return result
    }

    func max(nums []int) int {
        if len(nums) == 0 {
            panic("can't take max of empty slice")
        }

        result := nums[0]
        for _, n := range nums[1:] {
            if n > result {
                result = n
            }
        }
        return result
    }

    func median(nums []int) int {
        n := len(nums)
        if n == 0 {
            panic("can't take median of empty slice")
        }
        // make a copy of nums
        tmp := make([]int, len(nums))
        copy(tmp, nums)
        sort.Ints(tmp)
        return tmp[n/2]
    }

    func main() {
        // numbers.txt is assumed to have one integer per line
        file, err := os.Open("numbers.txt")

        // deferred statements are run after the function ends, even if the
        // function ends unexpectedly (e.g. by a call to panic)
        defer file.Close()

        // if err is not nil, then something went wrong opening the file
        // and so we immediately end the program by calling panic
        if err != nil {
            panic("couldn't open numbers.txt")
        }

        // read all the numbers into a slice
        nums := []int{} // nums is initially empty
        scanner := bufio.NewScanner(file)
        for scanner.Scan() {
            line := scanner.Text()
            n, err := strconv.Atoi(line)
            if err == nil {
                nums = append(nums, n)
            } else { // err != nil
                fmt.Printf("Couldn't convert \"%v\" to an int (skipping)\n", line)
            }
        } // for

        //
        // print some statistics about the numbers
        //
        fmt.Println(nums)
        fmt.Printf("   min: %v\n", min(nums))
        fmt.Printf("  mean: %0.3v\n", mean(nums))
        fmt.Printf("median: %v\n", median(nums))
        fmt.Printf("   max: %v\n", max(nums))
        fmt.Println(nums)
    } // main