parsing!

lex.go

@@ -10,27 +10,27 @@ type typ3 int
 
 const (
 	invalid typ3 = iota
-	int3ger
+	integerToken
-	symbol
+	symbolToken
-	openParen
+	openParenToken
-	closeParen
+	closeParenToken
-	str1ng
+	stringToken
-	fl0at
+	floatToken
 )
 
 func (t typ3) String() string {
 	switch t {
-	case int3ger:
+	case integerToken:
 		return "integer"
-	case symbol:
+	case symbolToken:
 		return "symbol"
-	case openParen:
+	case openParenToken:
 		return "open_paren"
-	case closeParen:
+	case closeParenToken:
 		return "close_paren"
-	case str1ng:
+	case stringToken:
 		return "string"
-	case fl0at:
+	case floatToken:
 		return "float"
 	}
 	panic("wtf")
@@ -85,7 +85,7 @@ func debugPrint(s string) {
 // lexes an open parenthesis
 func lexOpenParen(l *lexer) (stateFn, error) {
 	debugPrint("-->lexOpenParen")
-	l.out <- token{"(", openParen}
+	l.out <- token{"(", openParenToken}
 	l.depth++
 	r, _, err := l.ReadRune()
 	if err != nil {
@@ -146,7 +146,7 @@ func lexString(l *lexer) (stateFn, error) {
 	}
 	switch r {
 	case '"':
-		l.emit(str1ng)
+		l.emit(stringToken)
 		return lexWhitespace, nil
 	case '\\':
 		return lexStringEsc, nil
@@ -177,16 +177,16 @@ func lexInt(l *lexer) (stateFn, error) {
 	}
 	switch r {
 	case ' ', '\t', '\n', '\r':
-		l.emit(int3ger)
+		l.emit(integerToken)
 		return lexWhitespace, nil
 	case '.':
 		l.append(r)
 		return lexFloat, nil
 	case ')':
-		l.emit(int3ger)
+		l.emit(integerToken)
 		return lexCloseParen, nil
 	case ';':
-		l.emit(int3ger)
+		l.emit(integerToken)
 		return lexComment, nil
 	}
 	if isDigit(r) {
@@ -207,13 +207,13 @@ func lexFloat(l *lexer) (stateFn, error) {
 
 	switch r {
 	case ' ', '\t', '\n', '\r':
-		l.emit(fl0at)
+		l.emit(floatToken)
 		return lexWhitespace, nil
 	case ')':
-		l.emit(fl0at)
+		l.emit(floatToken)
 		return lexCloseParen, nil
 	case ';':
-		l.emit(fl0at)
+		l.emit(floatToken)
 		return lexComment, nil
 	}
 	if isDigit(r) {
@@ -234,13 +234,13 @@ func lexSymbol(l *lexer) (stateFn, error) {
 	switch r {
 	case ' ', '\t', '\n', '\r':
 		debugPrint("ending lexSymbol on whitespace")
-		l.emit(symbol)
+		l.emit(symbolToken)
 		return lexWhitespace, nil
 	case ')':
-		l.emit(symbol)
+		l.emit(symbolToken)
 		return lexCloseParen, nil
 	case ';':
-		l.emit(symbol)
+		l.emit(symbolToken)
 		return lexComment, nil
 	default:
 		l.append(r)
@@ -252,7 +252,7 @@ func lexSymbol(l *lexer) (stateFn, error) {
 // lex a close parenthesis
 func lexCloseParen(l *lexer) (stateFn, error) {
 	debugPrint("-->lexCloseParen")
-	l.out <- token{")", closeParen}
+	l.out <- token{")", closeParenToken}
 	l.depth--
 	r, _, err := l.ReadRune()
 	if err != nil {

skeam.go

@@ -2,13 +2,92 @@ package main
 
 import (
 	"bufio"
+    "errors"
 	"fmt"
 	"io"
 	"os"
+	"strconv"
 )
 
 var DEBUG = false
 
+type sexp []interface{}
+
+type symbol string
+
+// parses the string lexeme into a value that can be eval'd
+func atom(t token) (interface{}, error) {
+    switch t.t {
+    case integerToken:
+        val, err := strconv.ParseInt(t.lexeme, 10, 64)
+        if err != nil {
+            return nil, err
+        }
+        return val, nil
+
+    case floatToken:
+        val, err := strconv.ParseFloat(t.lexeme, 64)
+        if err != nil {
+            return nil, err
+        }
+        return val, nil
+
+    case stringToken:
+        return t.lexeme, nil
+
+    case symbolToken:
+        return symbol(t.lexeme), nil
+    }
+
+    return nil, fmt.Errorf("unable to atomize token: %v", t)
+}
+
+// reads in tokens on the channel until a matching close paren is found.
+func (s *sexp) readIn(c chan token) error {
+    for t := range c {
+        switch t.t {
+        case closeParenToken:
+            return nil
+        case openParenToken:
+            child := make(sexp, 0)
+            if err := child.readIn(c); err != nil {
+                return err
+            }
+            *s = append(*s, child)
+        default:
+            v, err := atom(t)
+            if err != nil {
+                return err
+            }
+            *s = append(*s, v)
+        }
+    }
+    return errors.New("unexpected EOF in sexp.readIn")
+}
+
+// parses one value that can be evaled from the channel
+func parse(c chan token) (interface{}, error) {
+    for t := range c {
+        switch t.t {
+        case closeParenToken:
+            return nil, errors.New("unexpected EOF in read")
+        case openParenToken:
+            s := make(sexp, 0)
+            if err := s.readIn(c); err != nil {
+                return nil, err
+            }
+            return s, nil
+        default:
+            return atom(t)
+        }
+    }
+    return nil, io.EOF
+}
+
+func eval(v interface{}) {
+    fmt.Println(v)
+}
+
 func args() {
 	filename := os.Args[1]
 	f, err := os.Open(filename)
@@ -21,9 +100,17 @@ func args() {
 	c := make(chan token, 32)
 	go lex(bufio.NewReader(f), c)
 
-	for s := range c {
+    for {
-		fmt.Printf("%11s %s\n", s.t, s.lexeme)
+        v, err := parse(c)
-	}
+        switch err {
+        case io.EOF:
+            return
+        case nil:
+            eval(v)
+        default:
+            fmt.Println("error in args(): %v", err)
+        }
+    }
 }
 
 func main() {
@@ -52,8 +139,17 @@ func main() {
 
 		c := make(chan token, 32)
 		go lexs(string(line)+"\n", c)
-		for s := range c {
+        for {
-			fmt.Printf("%11s %s\n", s.t, s.lexeme)
+            v, err := parse(c)
-		}
+            switch err {
+            case io.EOF:
+                goto OUT
+            case nil:
+                eval(v)
+            default:
+                fmt.Println("error in repl: %v", err)
+            }
+        }
+        OUT:
 	}
 }