138 lines
3.8 KiB
Go
138 lines
3.8 KiB
Go
package main
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import (
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"bufio"
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"errors"
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"fmt"
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"math"
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"os"
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"strconv"
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"strings"
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)
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const NORMAL90CONFIDENCE = 1.6448536269514727
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// Actually, I should look up how do do a) enums in go, b) union types
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type Lognormal struct {
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low float64
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high float64
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}
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type Dist struct {
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Type string
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Lognormal Lognormal
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Samples []float64
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}
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// Parse line into Distribution
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func parseLineErr(err_msg string) (string, Dist, error) {
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return "", Dist{}, errors.New(err_msg)
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}
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func parseLine(line string) (string, Dist, error) {
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words := strings.Split(strings.TrimSpace(line), " ")
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op := ""
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var dist Dist
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switch words[0] {
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case "*":
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op = "*"
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words = words[1:]
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case "/":
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op = "/"
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words = words[1:]
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case "+":
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return parseLineErr("+ operation not implemented yet")
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case "-":
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return parseLineErr("- operation not implemented yet")
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default:
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op = "*" // later, change the below to
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}
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switch len(words) {
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case 0:
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return parseLineErr("Can't operate on nothing")
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case 1:
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single_float, err1 := strconv.ParseFloat(words[0], 64)
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if err1 != nil {
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fmt.Println("Trying to operate on a scalar, but scalar is not a float")
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}
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dist = Dist{Type: "Lognormal", Lognormal: Lognormal{low: single_float, high: single_float}, Samples: nil}
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case 2:
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new_low, err1 := strconv.ParseFloat(words[0], 64)
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new_high, err2 := strconv.ParseFloat(words[1], 64)
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if err1 != nil || err2 != nil {
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return parseLineErr("Trying to operate by a distribution, but distribution is not specified as two floats")
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}
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dist = Dist{Type: "Lognormal", Lognormal: Lognormal{low: new_low, high: new_high}, Samples: nil}
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default:
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return parseLineErr("Other input methods not implemented yet")
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}
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return op, dist, nil
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}
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// Join distributions
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// Multiply lognormals
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func logBoundsToLogParams(low float64, high float64) (float64, float64) {
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loglow := math.Log(low)
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loghigh := math.Log(high)
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logmean := (loghigh + loglow) / 2.0
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logstd := (loghigh - loglow) / (2.0 * NORMAL90CONFIDENCE)
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return logmean, logstd
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}
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func logParamsToLogBounds(logmean float64, logstd float64) (float64, float64) {
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h := logstd * NORMAL90CONFIDENCE
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loglow := logmean - h
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loghigh := logmean + h
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return math.Exp(loglow), math.Exp(loghigh)
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}
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func multiplyLogParams(logmean1 float64, logstd1 float64, logmean2 float64, logstd2 float64) (float64, float64) {
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return logmean1 + logmean2, math.Sqrt(logstd1*logstd1 + logstd2*logstd2)
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}
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func multiplyLogBounds(old_low, old_high, new_low, new_high float64) (float64, float64) {
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logmean_old, logstd_old := logBoundsToLogParams(old_low, old_high)
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logmean_new, logstd_new := logBoundsToLogParams(new_low, new_high)
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logmean_product, logstd_product := multiplyLogParams(logmean_old, logstd_old, logmean_new, logstd_new)
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return logParamsToLogBounds(logmean_product, logstd_product)
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}
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func joinDists(old_dist Dist, new_dist Dist, op string) (Dist, error) {
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switch {
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case old_dist.Type == "Lognormal" && new_dist.Type == "Lognormal" && op == "*":
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low, high := multiplyLogBounds(old_dist.Lognormal.low, old_dist.Lognormal.high, new_dist.Lognormal.low, new_dist.Lognormal.high)
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return Dist{Type: "Lognormal", Lognormal: Lognormal{low: low, high: high}, Samples: nil}, nil
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default:
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fmt.Printf("For now, can't do anything besides multiplying lognormals")
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}
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return old_dist, errors.New("Error blah blah")
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}
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/* Main event loop */
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func main() {
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reader := bufio.NewReader(os.Stdin)
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old_dist := Dist{Type: "Lognormal", Lognormal: Lognormal{low: 1, high: 1}, Samples: nil} // Could also just be a scalar
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fmt.Printf("Hello world")
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EventForLoop:
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for {
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input, _ := reader.ReadString('\n')
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if strings.TrimSpace(input) == "" {
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continue EventForLoop
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}
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op, new_dist, err := parseLine(input)
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if err != nil {
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}
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joint_dist, err := joinDists(old_dist, new_dist, op)
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if err != nil {
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}
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old_dist = joint_dist
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}
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}
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