optimizations

internal/lexer/lexer.go

@@ -182,9 +182,7 @@ func (l *Lexer) NextToken() token.Token {
 			tok.Type = token.LookupIdent(tok.Literal)
 			return tok
 		} else if isDigit(l.ch) {
-			tok.Type = token.INT
-			tok.Literal = l.readNumber()
-			return tok
+			return l.readNumber()
 		} else {
 			tok = newToken(token.ILLEGAL, l.ch)
 		}
@@ -209,12 +207,22 @@ func (l *Lexer) readIdentifier() string {
 	return l.input[position:l.position]
 }
 
-func (l *Lexer) readNumber() string {
+func (l *Lexer) readNumber() token.Token {
 	position := l.position
 	for isDigit(l.ch) {
 		l.readChar()
 	}
-	return l.input[position:l.position]
+	intPart := l.input[position:l.position]
+	if l.ch == '.' {
+		l.readChar()
+		position := l.position
+		for isDigit(l.ch) {
+			l.readChar()
+		}
+		fracPart := l.input[position:l.position]
+		return token.Token{Type: token.FLOAT, Literal: intPart + "." + fracPart}
+	}
+	return token.Token{Type: token.INT, Literal: intPart}
 }
 
 func isLetter(ch byte) bool {

internal/lexer/lexer_test.go

@@ -210,3 +210,35 @@ c := "\r\n\t"
 	}
 
 }
+
+func TestFloats(t *testing.T) {
+	input := `2.5
+3.14
+`
+
+	tests := []struct {
+		expectedType    token.TokenType
+		expectedLiteral string
+	}{
+		{token.FLOAT, "2.5"},
+		{token.FLOAT, "3.14"},
+		{token.EOF, ""},
+	}
+
+	lexer := New(input)
+
+	for i, test := range tests {
+		token := lexer.NextToken()
+
+		if token.Type != test.expectedType {
+			t.Fatalf("tests[%d] - token type wrong. expected=%q, got=%q",
+				i, test.expectedType, token.Type)
+		}
+
+		if token.Literal != test.expectedLiteral {
+			t.Fatalf("tests[%d] - literal wrong. expected=%q, got=%q",
+				i, test.expectedLiteral, token.Literal)
+		}
+	}
+
+}