utils.go

package zeno

func isNegative(exp string, i *int) bool {
	n := len(exp)
	negativeSigns := 0
	for *i < n && exp[*i] == '-' {
		// in case user is really bored and started to add negative
		// signs before a number
		negativeSigns++
		*i++
	}
	*i--
	return negativeSigns%2 != 0
}

func signedExpression(exp string, signed bool) string {
	if signed {
		exp = "-" + exp
	}
	return exp
}

func isNum(c string) bool {
	return c >= "0" && c <= "9"
}

func isOperator(c string) bool {
	switch c {
	case "+", "-", "*", "/", "^", "(":
		return true
	}
	return false
}

func isLetter(c string) bool {
	return c >= "a" && c <= "z"
}

func isFunc(i *int, exp string, output *string) bool {
	*output = ""
	for ; *i < len(exp); *i++ {
		if !isLetter(string(exp[*i])) {
			*i--
			break
		}
		*output += string(exp[*i])
	}
	return len(*output) > 1
}

func precedence(c string) int {
	switch c {
	case "+", "-":
		return 2
	case "*", "/":
		return 3
	case "^":
		return 4
	}
	// functions
	return 5
}

func assocRight(c string) bool {
	return c == "^"
}