fermi/simple/f_minimal.go

141 lines
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2024-06-19 14:41:47 +00:00
package main
import (
"bufio"
"errors"
"fmt"
"git.nunosempere.com/NunoSempere/fermi/pretty"
"math"
"os"
"strconv"
"strings"
)
type Lognormal struct {
low float64
high float64
}
const HELP_MSG = " Operation | Variable assignment | Special\n" +
" Operation: operator operand\n" +
" operator: (empty) | * | / | + | -\n" +
" operand: scalar | lognormal\n" +
" lognormal: low high\n" +
" Clear stack: . | c | clear\n" +
" Other special operations: help | debug | exit\n" +
" Examples: \n" +
" / 2.5\n" +
" * 1 10 (interpreted as lognormal)\n" +
" / 1 10\n" +
" 1 10 (multiplication taken as default operation)\n" +
" .\n" +
" exit\n"
const NORMAL90CONFIDENCE = 1.6448536269514727
const N_SAMPLES = 100_000
func prettyPrintLognormal(l Lognormal) {
fmt.Printf("=> ")
pretty.PrettyPrint2Floats(l.low, l.high)
fmt.Println()
}
func printAndReturnErr(err_msg string) error {
fmt.Println(err_msg)
fmt.Println(HELP_MSG)
return errors.New(err_msg)
}
func multiplyLogDists(l1 Lognormal, l2 Lognormal) Lognormal {
logmean1 := (math.Log(l1.high) + math.Log(l1.low)) / 2.0
logstd1 := (math.Log(l1.high) - math.Log(l1.low)) / (2.0 * NORMAL90CONFIDENCE)
logmean2 := (math.Log(l2.high) + math.Log(l2.low)) / 2.0
logstd2 := (math.Log(l2.high) - math.Log(l2.low)) / (2.0 * NORMAL90CONFIDENCE)
logmean_product := logmean1 + logmean2
logstd_product := math.Sqrt(logstd1*logstd1 + logstd2*logstd2)
h := logstd_product * NORMAL90CONFIDENCE
loglow := logmean_product - h
loghigh := logmean_product + h
return Lognormal{low: math.Exp(loglow), high: math.Exp(loghigh)}
}
func divideLogDists(l1 Lognormal, l2 Lognormal) (Lognormal, error) {
if l2.high == 0 || l2.low == 0 {
fmt.Println("Error: Can't divide by 0.0")
return Lognormal{}, errors.New("Error: division by zero")
}
return multiplyLogDists(l1, Lognormal{low: 1.0 / l2.high, high: 1.0 / l2.low}), nil
}
func parseWordsErr(err_msg string) (string, Lognormal, error) {
return "", Lognormal{}, printAndReturnErr(err_msg)
}
func parseWordsIntoOpAndDist(words []string) (string, Lognormal, error) {
op := ""
var dist Lognormal
switch words[0] {
case "*", "/":
op = words[0]
words = words[1:]
default:
op = "*"
}
switch len(words) {
case 0:
return parseWordsErr("Operator must have operand; can't operate on nothing")
case 1:
single_float, err := strconv.ParseFloat(words[0], 64) // abstract this away to search for K/M/B/T/etc.
if err != nil {
return parseWordsErr("Trying to operate on a scalar, but scalar is neither a float nor an assigned variable")
}
dist = Lognormal{low: single_float, high: single_float}
case 2:
new_low, err1 := strconv.ParseFloat(words[0], 64)
new_high, err2 := strconv.ParseFloat(words[1], 64)
if err1 != nil || err2 != nil {
return parseWordsErr("Trying to operate by a distribution, but distribution is not specified as two floats")
}
dist = Lognormal{low: new_low, high: new_high}
default:
return parseWordsErr("Input not understood or not implemented yet")
}
return op, dist, nil
}
func main() {
reader := bufio.NewReader(os.Stdin)
old_dist := Lognormal{low: 1, high: 1}
replForLoop:
for {
new_line, _ := reader.ReadString('\n')
words := strings.Split(strings.TrimSpace(new_line), " ")
if strings.TrimSpace(new_line) == "" {
continue replForLoop
}
op, new_dist, err := parseWordsIntoOpAndDist(words)
if err != nil {
continue replForLoop
}
switch op {
case "*":
old_dist = multiplyLogDists(old_dist, new_dist)
case "/":
result_dist, err := divideLogDists(old_dist, new_dist)
if err != nil {
continue replForLoop
}
old_dist = result_dist
}
prettyPrintLognormal(old_dist)
}
}