Adds lexer and beginnings of parser

parser/lexer.go

@@ -0,0 +1,157 @@
+package parser
+
+import (
+  "bufio"
+  "bytes"
+  "io"
+  "strings"
+)
+
+type Token struct {
+  kind  int
+  val   string
+}
+
+type scanner struct {
+  r   *bufio.Reader
+}
+
+var eof rune = rune(0)
+
+const (
+  Number int = iota
+  Text
+  Opperator
+  Whitespace
+  Comment
+  Newline
+  End
+
+  Illegal
+)
+
+// - ~ + - ~ + //
+//  Receivers  //
+// - ~ + - ~ + //
+
+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() Token {
+  char := s.read()
+
+  if isWhitespace(char) {
+    s.unread()
+    return s.scanWhitespace()
+  } else if isLetter(char) {
+    s.unread()
+    return s.scanText()
+  } else if isNumber(char) {
+    s.unread()
+    return s.scanNumber()
+  } else if char == '#' {
+    s.unread()
+    return s.scanComment()
+  } else if isOpperator() {
+    return Token{Opperator, string(char)}
+  } else if char == '\n' {
+    return Token{Newline,""}
+  } else if char == eof {
+    return Token{End, ""}
+  }
+
+  return Token{illegal, string(char)}
+}
+
+
+func (s *scanner) scanWhitespace() Token {
+  var buf bytes.Buffer
+  buf.WriteRune(s.read())
+
+  for {
+    if ch := s.read(); ch == eof {
+      s.unread()
+      break
+    } else if !isWhitespace(ch) {
+      s.unread()
+      break
+    } else {
+      _, _ = buf.WriteRune(ch)
+    }
+  }
+
+  return Token{Whitespace, buf.String()}
+}
+
+
+func (s *scanner) scanText() Token {
+  var buf bytes.Buffer
+  buf.WriteRune(s.read())
+
+  for {
+    if ch := s.read(); ch == eof {
+      s.unread()
+      break
+    } else if !isLetter(ch) {
+      s.unread()
+      break
+    } else {
+      _, _ = buf.WriteRune(ch)
+    }
+
+    return Token{Text, buf.String()}
+  }
+}
+
+
+func (s *scanner) scanComment() {
+  var buf bytes.Buffer
+  buf.WriteRune(s.read())
+
+  for {
+    if ch := s.read(); ch == eof || ch == '\n' {
+      s.unread()
+      break
+    } else {
+      _, _ = buf.WriteRune(ch)
+    }
+  }
+
+  return Token{Comment, buf.String()}
+}
+
+
+// - ~ + - ~ + //
+// Functions   //
+// - ~ + - ~ + //
+
+func isWhitespace(ch rune) bool {
+  return ch == ' ' || ch == '\t' || ch == '\r'
+}
+
+func isLetter(ch rune) bool {
+  return ch >= 'A' && ch <= 'Z' || ch >= 'a' && ch <= 'z'
+}
+
+func isNumber(ch rune) bool {
+  return ch >= '0' && ch <= '9'
+}
+
+func  isOpperator(ch rune) bool {
+  return ch == '=' || ch == '+' || ch == '-' || ch == '*' || ch == '/' || ch == '^' || ch == '%'
+}
+
+func NewScanner(r io.Reader) *scanner {
+  return &scanner{r: bufio.NewReader(r)}
+}