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package circuitcompiler
import (
"bufio"
"bytes"
"io"
)
type OperatorSymbol int
type Token int
const (
ILLEGAL Token = iota
WS
EOF
IDENT // val
VAR // var
CONST // const value
EQ // =
PLUS // +
MINUS // -
MULTIPLY // *
DIVIDE // /
EXP // ^
OUT
)
var eof = rune(0)
func isWhitespace(ch rune) bool {
return ch == ' ' || ch == '\t' || ch == '\n'
}
func isLetter(ch rune) bool {
return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')
}
func isDigit(ch rune) bool {
return (ch >= '0' && ch <= '9')
}
type Scanner struct {
r *bufio.Reader
}
func NewScanner(r io.Reader) *Scanner {
return &Scanner{r: bufio.NewReader(r)}
}
func (s *Scanner) read() rune {
ch, _, err := s.r.ReadRune()
if err != nil {
return eof
}
return ch
}
func (s *Scanner) unread() {
_ = s.r.UnreadRune()
}
func (s *Scanner) Scan() (tok Token, lit string) {
ch := s.read()
if isWhitespace(ch) {
// space
s.unread()
return s.scanWhitespace()
} else if isLetter(ch) {
// letter
s.unread()
return s.scanIndent()
} else if isDigit(ch) {
s.unread()
return s.scanIndent()
}
switch ch {
case eof:
return EOF, ""
case '=':
return EQ, "="
case '+':
return PLUS, "+"
case '-':
return MINUS, "-"
case '*':
return MULTIPLY, "*"
case '/':
return DIVIDE, "/"
case '^':
return EXP, "^"
}
return ILLEGAL, string(ch)
}
func (s *Scanner) scanWhitespace() (token Token, lit string) {
var buf bytes.Buffer
buf.WriteRune(s.read())
for {
if ch := s.read(); ch == eof {
break
} else if !isWhitespace(ch) {
s.unread()
break
} else {
_, _ = buf.WriteRune(ch)
}
}
return WS, buf.String()
}
func (s *Scanner) scanIndent() (tok Token, lit string) {
var buf bytes.Buffer
buf.WriteRune(s.read())
for {
if ch := s.read(); ch == eof {
break
} else if !isLetter(ch) && !isDigit(ch) {
s.unread()
break
} else {
_, _ = buf.WriteRune(ch)
}
}
switch buf.String() {
case "var":
return VAR, buf.String()
}
if len(buf.String()) == 1 {
return Token(rune(buf.String()[0])), buf.String()
}
if buf.String() == "out" {
return OUT, buf.String()
}
return IDENT, buf.String()
}