如何访问 antlr golang 目标中的语法组件 [英] how to access grammar components in antlr golang target
问题描述
访问通过语法规则传递的运算符值时出现编译错误.例如,我有以下语法文件:
I am getting a compile error when accessing the operator value passed through the grammar rules. For example, I have the following grammar file:
grammar Expr;
@parser::header {
import (
"os"
)
}
@parser::members {
func eval(left int, op antlr.Token, right int) int {
if (op.GetText() == "*") {
return left * right
} else if (op.GetText() == "+") {
return left + right
} else if (op.GetText() == "-") {
return left - right
} else {
return 0
}
}
}
stat: e NEWLINE
| NEWLINE
;
e returns [int v]
: a=e op=('+'|'-') b=e {
$v = eval($a.v, $op, $b.v)
fmt.Fprintf(os.Stdout, "got args=%d %d\n", $a.v, $b.v)
}
| INT {
$v = $INT.int
fmt.Fprintf(os.Stdout, "got number=%d\n", $v)
}
;
MUL : '*' ;
DIV : '/' ;
ADD : '+' ;
SUB : '-' ;
ID : [a-zA-Z]+ ; // match identifiers
INT : [0-9]+ ; // match integers
NEWLINE:'\r'? '\n' ; // return newlines to parser (is end-statement signal)
WS : [ \t]+ -> skip ; // toss out whitespace
这是测试代码:
package main
import (
"os"
"./parser"
"github.com/antlr/antlr4/runtime/Go/antlr"
)
func calc(inputfile string) {
input, _ := antlr.NewFileStream(inputfile)// Setup the input
lexer := parser.NewExprLexer(input)// Create the Lexer
stream := antlr.NewCommonTokenStream(lexer, antlr.TokenDefaultChannel)
p := parser.NewExprParser(stream)// Create the Parser
p.Stat()
}
func main() {
calc(os.Args[1])
}
这些是我运行的命令:
java org.antlr.v4.Tool -Dlanguage=Go -o parser -no-listener Expr.g4
go build expr_t.go
以上 2 个程序运行正常.但是,如果我将 eval 函数的比较更改为如下所示的内容,则会出现编译错误(类型不匹配):
The above 2 programs work correctly. But I get a compile error (type mismatch) if I change the eval function's comparisons to something like this:
if (op.tokenType == ExprParserMUL) {
return left * right
如何获取 op 的值与 ExprParseMUL 进行比较?
How to get the op's value for comparison with ExprParseMUL?
推荐答案
if (op.tokenType == ExprParserMUL) {
return left * right
如何获取 op 的值与 ExprParseMUL 进行比较?
How to get the op's value for comparison with ExprParseMUL?
没有 tokenType
字段.使用 GetTokenType()
.
There isn't a tokenType
field. Use GetTokenType()
.
参见:https://github.com/antlr/antlr4/blob/master/runtime/Go/antlr/token.go
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