secret-handshake, and others: use %q to make difference between [""] and [] clear

[Insti]

"go path secret handshake does not work properly": exercism/exercism#3239

---

package secret

import (
	"regexp"
	"strconv"
)

const testVersion = 1

var cases = map[int]string{
	0: "wink",
	1: "double blink",
	2: "close your eyes",
	3: "jump",
	4:"reverse",
}

//Handshake function returns the encrypted human readable handshake
func Handshake(inp uint) []string {
	var in = strconv.Itoa(int(inp))
	if in == "0" {
		return nil
	}
	isDecimal := regexp.MustCompile("[2-9]")
	if isDecimal.MatchString(in) {
		num, _ := strconv.Atoi(in)
		in = strconv.FormatInt(int64(num), 2)
	}
	reverse := false
	out := make([]string, 0, 4)
	ln := len(in) - 1
	for num, val := range in {
		if ln-num == 4 {
			reverse = true
			continue
		}
		if string(val) == "1" {
			out = append(out, cases[ln-num])
		}
	}
	if !reverse {
		for i, j := 0, len(out)-1; i < j; i, j = i+1, j-1 {
			out[i], out[j] = out[j], out[i]
		}
	}
	return out
}

[petertseng]

the posted implementation returns [""] for Handshake(32) (slice of one element, the empty string), whereas the two acceptable answers are either nil or [] (slice of zero elements)

This can be made clear by changing %v to %q in the test code, then you will see this:

--- FAIL: TestHandshake (0.00s)
	a_test.go:38: Handshake(32) = [""], want [].

I suggest the test file be updated to use %q to resolve this issue: https://play.golang.org/p/jG_SJMzJvP

[petertseng]

also consider using %q in the following exercises that may expect []strings:

• accumulate (low-pri, is deprecated) (accumulate: update tests #567)
• allergies (update test formatting, response to #414 #422)
• anagram (update test formatting, response to #414 #422)
• binary-search-tree (uses %q appropriately)
• custom-set (uses %q appropriately)
• grade-school (update test formatting, response to #414 #422)
• kindergarten-garden (kindergarten-garden: update test output formatting #564)
• ocr-numbers (uses %q appropriately)
• poker (uses %#v appropriately - https://play.golang.org/p/NJ--RgJTpj)
• pov (prints each edge on separate line and counts them, will not get confused)
• protein-translation (uses %q appropriately)
• secret-handshake (original cause of this issue) (update test formatting, response to #414 #422)
• series (series: update to use %q #535)
• strain (strain: update tests #538 makes it use %#v)

(I just grepped for []string, but I think I did not miss any)

Anyone working on these is free to work on either just a single one of these, or all the remaining ones (just three left as of this writing)

[robphoenix]

🎉