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Make IntRange explicitly inclusive to [min, max]. #5

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Make IntRange explicitly inclusive to [min, max]. #5

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26 changes: 11 additions & 15 deletions randutil.go
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Original file line number Diff line number Diff line change
Expand Up @@ -21,23 +21,19 @@ const (

var MinMaxError = errors.New("Min cannot be greater than max.")

// IntRange returns a random integer in the range from min to max.
// IntRange returns a random integer in the range from min to max inclusive.
func IntRange(min, max int) (int, error) {
var result int
switch {
case min > max:
if min > max {
// Fail with error
return result, MinMaxError
case max == min:
result = max
case max > min:
maxRand := max - min
b, err := rand.Int(rand.Reader, big.NewInt(int64(maxRand)))
if err != nil {
return result, err
}
result = min + int(b.Int64())
}
maxRand := max - min + 1
b, err := rand.Int(rand.Reader, big.NewInt(int64(maxRand)))
if err != nil {
return result, err
}
result = min + int(b.Int64())
return result, nil
}

Expand Down Expand Up @@ -92,7 +88,7 @@ func AlphaString(n int) (string, error) {
func ChoiceString(choices []string) (string, error) {
var winner string
length := len(choices)
i, err := IntRange(0, length)
i, err := IntRange(0, length - 1)
winner = choices[i]
return winner, err
}
Expand All @@ -101,7 +97,7 @@ func ChoiceString(choices []string) (string, error) {
func ChoiceInt(choices []int) (int, error) {
var winner int
length := len(choices)
i, err := IntRange(0, length)
i, err := IntRange(0, length - 1)
winner = choices[i]
return winner, err
}
Expand All @@ -126,7 +122,7 @@ func WeightedChoice(choices []Choice) (Choice, error) {
for _, c := range choices {
sum += c.Weight
}
r, err := IntRange(0, sum)
r, err := IntRange(0, sum - 1)
if err != nil {
return ret, err
}
Expand Down