Type check

lex.go

@@ -3,6 +3,7 @@ package main
 import (
 	"fmt"
 	"regexp"
+	"slices"
 	"strconv"
 	"strings"
 )
@@ -37,9 +38,9 @@ type Id string
 
 type Token token[string]
 
-type Int token[int]
+type IntToken token[int]
 
-type Float token[float64]
+type FloatToken token[float64]
 
 type Identifier token[Id]
 
@@ -52,13 +53,16 @@ var (
 	SingleQuote = &Token{value: "'"}
 	Let         = &Token{value: "let"}
 	LambdaTok   = &Token{value: "lambda"}
+	If          = &Token{value: "if"}
+	TrueTok     = &Token{value: "t"}
+	NilTok      = &Token{value: "nil"}
 )
 
 func (t Token) String() string {
 	return fmt.Sprint(t.value)
 }
 
-func (t Int) String() string {
+func (t IntToken) String() string {
 	return fmt.Sprint(t.value)
 }
 
@@ -75,6 +79,9 @@ var knownTokens = []*Token{
 	SingleQuote,
 	Let,
 	LambdaTok,
+	If,
+	TrueTok,
+	NilTok,
 }
 
 func (t *Token) Equals(a Lexeme) bool {
@@ -86,8 +93,8 @@ func (t *Token) Equals(a Lexeme) bool {
 	}
 }
 
-func (t *Int) Equals(a Lexeme) bool   { return false }
-func (t *Float) Equals(a Lexeme) bool { return false }
+func (t *IntToken) Equals(a Lexeme) bool   { return false }
+func (t *FloatToken) Equals(a Lexeme) bool { return false }
 
 func (t *Identifier) Equals(a Lexeme) bool {
 	switch x := a.(type) {
@@ -110,6 +117,15 @@ func lex(source string) (*Input, error) {
 outer:
 	for len(source) > 0 {
 		p := position{pos: pos, line: line, column: column, filepath: "stdin"}
+		if source[0] == ';' {
+			idx := slices.Index([]byte(source), '\n')
+			if idx < 0 {
+				break
+			} else {
+				source = source[idx:]
+				continue
+			}
+		}
 		for _, try := range knownTokens {
 			if !strings.HasPrefix(source, try.value) {
 				continue
@@ -137,7 +153,7 @@ outer:
 			a := source[index[0]:index[1]]
 			conv, err := strconv.ParseFloat(a, 64)
 			if err == nil {
-				var i = &Float{position: p, value: conv}
+				var i = &FloatToken{position: p, value: conv}
 				tokens = append(tokens, i)
 				l := len(a)
 				source = source[l:]
@@ -151,7 +167,7 @@ outer:
 			a := source[index[0]:index[1]]
 			conv, err := strconv.Atoi(a)
 			if err == nil {
-				var i = &Int{position: p, value: conv}
+				var i = &IntToken{position: p, value: conv}
 				tokens = append(tokens, i)
 				l := len(a)
 				source = source[l:]