FindValidTokenCharacters.go

package main

import (
	"fmt"
	"go/scanner"
	"go/token"
	"math"
	"sync"
	"time"
)

func main() {
	fmt.Println("START     | END      | PASSES   | FAILS    | TOTAL    | TIME     ")

	var wg sync.WaitGroup
	h := 0
	limit := int(math.Pow(2, 16))
	size := limit / int(math.Pow(2, 10))
	for ; h+size <= limit; h += size {
		wg.Add(1)
		go func(a, b int) {
			defer wg.Done()
			passCount, failCount := 0, 0
			var r rune
			r += rune(a)
			//ri := r
			var i int
			start := time.Now()

			var fset *token.FileSet
			var s scanner.Scanner
			var src string
			var file *token.File

			for i = a; i < b; i++ {
				src = fmt.Sprintf("%c := 0\n", r)
				fset = token.NewFileSet()
				file = fset.AddFile("", fset.Base(), len(src))
				s.Init(file, []byte(src), nil /* no error handler */, scanner.ScanComments)
				for {
					_, tok, _ := s.Scan()
					if tok == token.EOF {
						break
					}

					if tok == token.ILLEGAL {
						failCount++
					} else if tok == token.IDENT {
						passCount++
					}
				}
				r++
			}
			fmt.Printf(" %8d | %8d | %8d | %8d | %8d | %s \n", a, b, passCount, failCount, b-a, time.Since(start))
		}(h, h+size-1)
	}

	wg.Wait()
}

I wrote this after finding that some Unicode characters did not work as valid character tokens. I wanted to use U+2203, the Existential 'THERE EXISTS' character in a private method and go complained. Also I used it to practice using goroutines.