Method concat

vm.go:172–217

(total int)

}

func (l *State) concat(total int) {
	t := func(i int) value { return l.stack[l.top-i] }
	put := func(i int, v value) { l.stack[l.top-i] = v }
	concatTagMethod := func() {
		if v, ok := l.callBinaryTagMethod(t(2), t(1), tmConcat); !ok {
			l.concatError(t(2), t(1))
		} else {
			put(2, v)
		}
	}
	l.assert(total >= 2)
	for total > 1 {
		n := 2 // # of elements handled in this pass (at least 2)
		s2, ok := t(2).(string)
		if !ok {
			_, ok = t(2).(float64)
		}
		if !ok {
			concatTagMethod()
		} else if s1, ok := l.toString(l.top - 1); !ok {
			concatTagMethod()
		} else if len(s1) == 0 {
			v, _ := l.toString(l.top - 2)
			put(2, v)
		} else if s2, ok = t(2).(string); ok && len(s2) == 0 {
			put(2, t(1))
		} else {
			// at least 2 non-empty strings; scarf as many as possible
			ss := []string{s1}
			for ; n <= total; n++ {
				if s, ok := l.toString(l.top - n); ok {
					ss = append(ss, s)
				} else {
					break
				}
			}
			n-- // last increment wasn't valid
			for i, j := 0, len(ss)-1; i < j; i, j = i+1, j-1 {
				ss[i], ss[j] = ss[j], ss[i]
			}
			put(len(ss), strings.Join(ss, ""))
		}
		total -= n - 1 // created 1 new string from `n` strings
		l.top -= n - 1 // popped `n` strings and pushed 1
	}
}

func (l *State) traceExecution() {
	callInfo := l.callInfo