func (me expression) Value() (lex.Token, bool) {
expression := []lex.Token(me)
size := len(expression)
if size == 0 {
var t lex.Token
t.SetInt(0)
return t, true
}
//and/or operators
for i := 0; i < size; i++ {
if expression[i].Type() == lex.Symbol {
o := expression[i]
switch o.String() {
case "&&", "||":
var tree parseTree
tree.build(expression, i)
return tree.Value()
}
}
}
//not operator
for i := 0; i < size; i++ {
if expression[i].Type() == lex.Symbol {
if expression[i].String() == "!" {
var tree parseTree
tree.build(expression, i)
return tree.Value()
}
}
}
//comparison operators
for i := 0; i < size; i++ {
if expression[i].Type() == lex.Symbol {
o := expression[i]
switch o.String() {
case "<", ">", "<=", ">=", "!=", "==":
var tree parseTree
tree.build(expression, i)
return tree.Value()
}
}
}
//add and subtract
for i := 0; i < size; i++ {
if expression[i].Type() == lex.Symbol {
if expression[i].String() == "+" || expression[i].String() == "-" {
var tree parseTree
tree.build(expression, i)
return tree.Value()
}
}
}
//multiplication and division
for i := 0; i < size; i++ {
if expression[i].Type() == lex.Symbol {
if expression[i].String() == "*" || expression[i].String() == "/" {
var tree parseTree
tree.build(expression, i)
return tree.Value()
}
}
}
var t lex.Token
if expression[0].Type() != lex.Symbol {
t = expression[0]
} else if expression[0].Type() == lex.Symbol { //is negative int literal
var t lex.Token
if expression[0].String() == "i" {
retval, _ := strconv.Atoi(expression[1].String())
t.SetInt(-retval)
return t, true
} else {
return t, false
}
}
return t, true
}
