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parser.go
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parser.go
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package mapq
// Parser 语法分析器
type Parser struct {
lexer *Lexer
}
func Getlevel(code int) (level int) {
//0: )
//3: + -
//4: * /
//1: || &&
//2: == >= <= > < != !
//5: (
//code := Binnode.Op
if code == TYPE_PLUS || code == TYPE_SUB {
return 3
} else if code == TYPE_MUL || code == TYPE_DIV {
return 4
} else if code == TYPE_OR || code == TYPE_AND || code == TYPE_NOT {
return 1
} else if code == TYPE_EQ || code == TYPE_LG || code == TYPE_SM || code == TYPE_LEQ || code == TYPE_SEQ || code == TYPE_NEQ {
return 2
} else if code == TYPE_LP {
return 0
} else if code == TYPE_RP {
return -1
}
return 404
}
func IsOper(token string) bool {
switch token {
case "+", "-", "*", "/", "==", ">=", "<=", "!=", ">", "<", "!", "(", ")", "||", "&&":
return true
}
return false
}
func PopNum(Numstack []BinNode) (x, y BinNode) {
x = Numstack[len(Numstack)-1]
y = Numstack[len(Numstack)-2]
//Numstack = Numstack[0 : len(Numstack)-2]
return x, y
}
func PopBin(Binstack []BinNode) (x BinNode) {
x = Binstack[len(Binstack)-1]
//Binstack = Binstack[0 : len(Binstack)-1]
return x
}
// 你的递归下降分析代码(如果你使用递归下降的话
// func (p *Parser) boolexp() (node Node, err error) {
// panic("not implemented")
// }
// func (p *Parser) boolean() (node Node, err error) {
// panic("not implemented")
// }
// 别的分析函数
// 。。。。。
// Parse 生成ast
//str:"a+b==3" 类似表达式
//Parse 生成AST树
func (p *Parser) Parse(str string) (n BinNode, err error) {
//panic("not implemented")
var l Lexer
p.lexer = &l
p.lexer.input = str
var Numstack []BinNode
var Binstack []BinNode
var fintoken string = ""
for code, token, eos := p.lexer.Scan(); eos; {
if code == TYPE_INT || code == TYPE_FLOAT || code == TYPE_VAR || code == TYPE_RES_TRUE ||
code == TYPE_RES_FALSE || code == TYPE_RES_NULL || code == TYPE_STR {
fintoken += token
temtoken, err := p.lexer.ScanType(TYPE_DOT)
if err == nil {
fintoken += temtoken
} else {
Numnode := BinNode{Token: fintoken, Diff: 0, Op: code}
Numstack = append(Numstack, Numnode)
fintoken = ""
}
}
//code 为 +-*/ () && || == > < >= <= != !
if IsOper(token) {
if token == "(" {
var Binnode BinNode
Binnode = BinNode{Op: code, Token: token, Diff: 2}
Binstack = append(Binstack, Binnode)
code, token, eos = p.lexer.Scan()
continue
}
if len(Binstack) == 0 || Getlevel(code) >= Getlevel(Binstack[len(Binstack)-1].Op) { //如果当前token的运算优先级大,则直接入栈
var Binnode BinNode
if token == "!" {
Binnode = BinNode{Op: code, Token: token, Diff: 1}
} else {
Binnode = BinNode{Op: code, Token: token, Diff: 2}
}
Binstack = append(Binstack, Binnode)
}
if Getlevel(code) < Getlevel(Binstack[len(Binstack)-1].Op) {
for len(Binstack) > 0 && Getlevel(code) < Getlevel(Binstack[len(Binstack)-1].Op) { //若小,则栈顶元素pop,左右节点为Num栈的顶二元素,同时Bin1再次入Num栈
Bin1 := PopBin(Binstack)
Binstack = Binstack[0 : len(Binstack)-1]
if token == ")" && Bin1.Token == "(" {
break
}
if Bin1.Token == "(" || Bin1.Token == ")" {
continue
}
if Bin1.Token == "!" {
Num1 := Numstack[len(Numstack)-1]
Numstack = Numstack[0 : len(Numstack)-1]
Bin1.Left = &Num1
Numstack = append(Numstack, Bin1)
} else {
Num1, Num2 := PopNum(Numstack) //直达Bin栈栈顶元素优先级小于token
Numstack = Numstack[0 : len(Numstack)-2]
Bin1.Left = &Num2
Bin1.Right = &Num1
Numstack = append(Numstack, Bin1)
}
}
if token == ")" {
code, token, eos = p.lexer.Scan()
continue
}
var Binnode BinNode
if token == "!" {
Binnode = BinNode{Op: code, Token: token, Diff: 1}
} else {
Binnode = BinNode{Op: code, Token: token, Diff: 2}
}
Binstack = append(Binstack, Binnode) ////已经小于,入栈
}
}
code, token, eos = p.lexer.Scan()
}
for len(Binstack) > 0 {
if Binstack[len(Binstack)-1].Diff == 1 {
Bin := PopBin(Binstack)
Binstack = Binstack[0 : len(Binstack)-1]
Num1 := Numstack[len(Numstack)-1]
Numstack = Numstack[0 : len(Numstack)-1]
Bin.Left = &Num1
Numstack = append(Numstack, Bin)
} else {
Bin1 := PopBin(Binstack)
Binstack = Binstack[0 : len(Binstack)-1]
if Bin1.Token == ")" {
continue
}
Num1, Num2 := PopNum(Numstack)
Numstack = Numstack[0 : len(Numstack)-2]
Bin1.Left = &Num2
Bin1.Right = &Num1
Numstack = append(Numstack, Bin1)
}
}
return Numstack[0], nil
}