/
main.go
72 lines (63 loc) · 1.38 KB
/
main.go
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package main
import(
"fmt"
"bytes"
"log"
"io/ioutil"
)
const(
MAX_LEXEME_LENGTH = 128
)
func main() {
str := getProgram("example.wb")
fmt.Printf("Input:\n%s\nOutput:\n",str)
program := bytes.NewReader(str)
for i:=0;i<program.Len();i++ {
lexeme,token:=lex(program)
fmt.Printf("Next token is: %s Next lexeme is: %s\n",getTokenString(token),lexeme)
}
}
func lex(program *bytes.Reader) (string,int) {
lexeme:=make([]rune,0,128)
index:=0
//Get next Non-Whitespace Character
char,_,err:=program.ReadRune()
for ;charClass(char)==WHITESPACE; {
errCheck(err)
char,_,err = program.ReadRune()
}
switch charClass(char) {
case LETTER: //IDENT or KEYWORD
for ;charClass(char)==LETTER||charClass(char)==DIGIT;char,_,err=program.ReadRune() {
errCheck(err)
lexeme=lexeme[:index+1]
lexeme[index]=char
index++
}
program.UnreadRune()
result:=string(lexeme)
return result,getKeyword(result)
case DIGIT:
for ;charClass(char)==DIGIT;char,_,err=program.ReadRune() {
errCheck(err)
lexeme=lexeme[:index+1]
lexeme[index]=char
index++
}
program.UnreadRune()
return string(lexeme),DIGIT
}
lexeme=lexeme[:index+1]
lexeme[index]=char
return string(lexeme),charClass(char)
}
func getProgram(filename string) (contents []byte) {
contents,err:=ioutil.ReadFile(filename)
errCheck(err)
return
}
func errCheck(err error) {
if err!=nil {
log.Fatal(err.Error())
}
}