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package main
import (
"log"
"github.com/alecthomas/repr"
"github.com/alecthomas/participle/v2"
"github.com/alecthomas/participle/v2/lexer"
)
type Terminal struct {
String *String ` @@`
Ident string `| @Ident`
}
type Expr struct {
Left *Terminal `@@`
Op string `( @Oper`
Right *Terminal ` @@)?`
}
type Fragment struct {
Escaped string `( @Escaped`
Expr *Expr ` | "${" @@ "}"`
Text string ` | @Char)`
}
type String struct {
Fragments []*Fragment `"\"" @@* "\""`
}
var (
def = lexer.MustStateful(lexer.Rules{
"Root": {
{`String`, `"`, lexer.Push("String")},
},
"String": {
{"Escaped", `\\.`, nil},
{"StringEnd", `"`, lexer.Pop()},
{"Expr", `\${`, lexer.Push("Expr")},
{"Char", `\$|[^$"\\]+`, nil},
},
"Expr": {
lexer.Include("Root"),
{`Whitespace`, `\s+`, nil},
{`Oper`, `[-+/*%]`, nil},
{"Ident", `\w+`, nil},
{"ExprEnd", `}`, lexer.Pop()},
},
})
parser = participle.MustBuild[String](participle.Lexer(def),
participle.Elide("Whitespace"))
)
func main() {
actual, err := parser.ParseString("", `"hello $(world) ${first + "${last}"}"`)
repr.Println(actual)
if err != nil {
log.Fatal(err)
}
}
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