diff --git a/tokenizer.c b/tokenizer.c
index 314735e..58bc3a6 100644
--- a/tokenizer.c
+++ b/tokenizer.c
@@ -8,185 +8,247 @@
 #include "os.h"
 #include "s8slice.h"
 
+#if 0
+#define log_trace(...) fprintf(stderr, __VA_ARGS__)
+#else
+#define log_trace(...)
+#endif
+
+
 typedef struct Parser {
-	S8Slice file;
-	int64_t cursor; 
+    S8Slice file;
+    int64_t cursor; 
 } Parser;
 
 typedef struct Token {
-	enum {
-		TOKEN_UNDEFINED,
-		TOKEN_INT,
-		TOKEN_IDENTIFIER,
-		TOKEN_STRING,
-		TOKEN_SYNTAX_ERROR,
-		TOKEN_EOF,
-	} kind;
-	union {
-		S8Slice identifier;
-		S8Slice string;
-		int     integer;
-	};
+    enum {
+        TOKEN_UNDEFINED,
+        TOKEN_INT,
+        TOKEN_ID,
+        TOKEN_STRING,
+        TOKEN_SYNTAX_ERROR,
+        TOKEN_EOS,
+        TOKEN_EOF,
+    } kind;
+    union {
+        S8Slice identifier;
+        S8Slice string;
+        int     integer;
+        char    undefined;
+    };
 } Token;
 
+const char* token_kind_str[] = {
+    [TOKEN_UNDEFINED]    = "TOKEN_UNDEFINED",
+    [TOKEN_INT]          = "TOKEN_INT",
+    [TOKEN_ID]           = "TOKEN_ID",
+    [TOKEN_STRING]       = "TOKEN_STRING",
+    [TOKEN_SYNTAX_ERROR] = "TOKEN_SYNTAX_ERROR",
+    [TOKEN_EOS]          = "TOKEN_EOS",
+    [TOKEN_EOF]          = "TOKEN_EOF",
+};
+
 Parser parser_attach(S8Slice file)
 {
-	return (Parser){.file = file, .cursor = 0};
+    return (Parser){.file = file, .cursor = 0};
 }
 
 static int parser_peek(Parser* p)
 {
-	const int ch = p->cursor >= p->file.len
-		? EOF
-		: (int)p->file.data[p->cursor];
-	return ch;
+    const int ch = p->cursor >= p->file.len
+        ? EOF
+        : (int)p->file.data[p->cursor];
+    log_trace("peeking:\t%c\n", isprint(ch) ? ch : '?');
+    return ch;
 }
 
 static int parser_getch(Parser* p)
 {
-	const int ch = p->cursor >= p->file.len
-		? EOF
-		: (int)p->file.data[p->cursor];
-	p->cursor += 1;
-	if (ch == '\n' && parser_peek(p) == '\r') {
-		p->cursor += 1;
-	}
-	return ch;
+    const int ch = p->cursor >= p->file.len
+        ? EOF
+        : (int)p->file.data[p->cursor];
+    p->cursor += 1;
+    log_trace(stderr, "getch:\t%c\n", isprint(ch) ? ch : '?');
+    if (ch == '\n' && p->file.data[p->cursor] == '\r') {
+        p->cursor += 1;
+    }
+    return ch;
+}
+
+static void parser_skip_char(Parser* p)
+{
+    const int ch = parser_getch(p);
+    log_trace(stderr, "skipping:\t%c\n", isprint(ch) ? ch : '?');
 }
 
 static void parser_ungetch(Parser* p)
 {
-	if (p->cursor > 0) {
-		p->cursor -= 1;
-	}
+    log_trace(stderr, "ungetch:\n");
+    if (p->cursor > 0) {
+        p->cursor -= 1;
+    }
+    if (p->file.data[p->cursor] == '\r') {
+        p->cursor -= 1;
+    }
 }
 
-static void parser_discard(Parser* p, int (*f) (int))
+static inline void parser_discard(Parser* p, int (*f) (int))
 {
-	int ch;
-	while (ch = parser_getch(p), f(ch))
-		/* noop */;
-	if (ch != EOF)
-		parser_ungetch(p);
+    int ch;
+    while (ch = parser_getch(p), f(ch))
+        /* noop */;
+    if (ch != EOF)
+        parser_ungetch(p);
 }
 
 static Token read_integer(Parser* p)
 {
-	/* FIXME: add support for 0x prefixes */
+    /* FIXME: add support for 0x prefixes */
 
-	/* the first char should be guaranteed to be isdigit */
-	assert(isdigit(parser_peek(p)));
+    /* the first char should be guaranteed to be isdigit */
+    assert(isdigit(parser_peek(p)));
 
-	int ch = EOF;
-	int n = 0;
-	while (ch = parser_getch(p), isdigit(ch)) {
-		n *= 10;
-		n += ch - '0';
-	}
-	parser_ungetch(p);
+    int ch = EOF;
+    int n = 0;
+    while (ch = parser_getch(p), isdigit(ch)) {
+        n *= 10;
+        n += ch - '0';
+    }
+    parser_ungetch(p);
 
-	Token t = {.kind = TOKEN_INT, .integer = n};
+    Token t = {.kind = TOKEN_INT, .integer = n};
 
-	return t;
+    return t;
+}
+
+int is_identifier_tail(int ch)
+{
+    return isalnum(ch) || ch == '_';
 }
 
 static Token read_identifier(Parser* p)
 {
-	int ch = EOF;
+    int ch = EOF;
 
-	/* the first char should be guaranteed to be isalpha */
-	assert(isalpha(parser_peek(p)));
+    /* the should be checked by the caller */
+    assert(isalpha(parser_peek(p)));
 
-	int64_t begin = p->cursor;
-	while (ch = parser_getch(p), isalnum(ch))
-		/* NOOP */;
-	parser_ungetch(p);
-	int64_t end = p->cursor;
+    int64_t begin = p->cursor;
+    while (ch = parser_getch(p), is_identifier_tail(ch))
+        /* NOOP */;
+    parser_ungetch(p);
+    int64_t end = p->cursor;
 
-	Token t = {
-		.kind = TOKEN_IDENTIFIER,
-		.identifier = s8slice(&p->file, begin, end)
-	};
+    Token t = {
+        .kind = TOKEN_ID,
+        .identifier = s8slice(&p->file, begin, end)
+    };
 
-	return t;
+    return t;
 }
 
 static Token read_string(Parser* p)
 {
-	int ch = EOF;
+    int ch = EOF;
 
-	/* the first char should be guaranteed to be '"' */
-	assert(parser_peek(p) == '"');
+    /* the first char should be guaranteed to be '"' */
+    assert(parser_peek(p) == '"');
 
-	(void)parser_getch(p); /* skip quote */
-	int64_t begin = p->cursor;
-	while (ch = parser_getch(p), ch != '"' && ch != '\n' && ch != EOF)
-		/* NOOP */;
-	if (ch != '"') {
-		fprintf(stderr, "syntax error: expected \", found %c\n", ch);
-		exit(EXIT_FAILURE);
-	}
-	int64_t end = p->cursor - 1; /* subtract one to ignore end quote */
+    (void)parser_getch(p); /* skip quote */
+    int64_t begin = p->cursor;
+    while (ch = parser_getch(p), ch != '"' && ch != '\n' && ch != EOF)
+        /* NOOP */;
+    if (ch != '"') {
+        fprintf(stderr, "syntax error: expected \", found %c\n", ch);
+        exit(EXIT_FAILURE);
+    }
+    int64_t end = p->cursor - 1; /* subtract one to ignore end quote */
 
-	Token t = {
-		.kind = TOKEN_STRING,
-		.identifier = s8slice(&p->file, begin, end)
-	};
+    Token t = {
+        .kind = TOKEN_STRING,
+        .identifier = s8slice(&p->file, begin, end)
+    };
 
-	return t;
+    return t;
 }
 
 static Token read_token(Parser* p)
 {
-	int ch = parser_peek(p);
+    int ch = parser_peek(p);
 
-	Token t;
+    Token t;
 
-	if (ch == EOF) {
-		t.kind = TOKEN_EOF;
-	} else if (isalpha(ch)) {
-		t = read_identifier(p);
-	} else if (isdigit(ch)) {
-		t = read_integer(p);
-	} else if (ch == '"') {
-		t = read_string(p);
-	}
+    if (ch == EOF) {
+        t.kind = TOKEN_EOF;
+    }
+    else if (ch == '\n') {
+        t.kind = TOKEN_EOS;
+        parser_skip_char(p);
+        parser_discard(p, isspace);
+    }
+    else if (isalpha(ch)) {
+        t = read_identifier(p);
+    }
+    else if (isdigit(ch)) {
+        t = read_integer(p);
+    }
+    else if (ch == '"') {
+        t = read_string(p);
+    } else {
+        t.kind = TOKEN_UNDEFINED;
+        t.undefined = ch;
+        parser_skip_char(p);
+    }
 
-	return t;
+    return t;
+}
+
+int isspace_except_newline(int ch)
+{
+    return isspace(ch) && (ch != '\n');
 }
 
 int main(int argc, char** argv)
 {
-	if (argc != 2) {
-		fprintf(stderr, "Usage: %s <file>\n", argv[0] ? argv[0] : "program");
-		exit(EXIT_FAILURE);
-	}
+    if (argc != 2) {
+        fprintf(stderr, "Usage: %s <file>\n", argv[0] ? argv[0] : "program");
+        exit(EXIT_FAILURE);
+    }
 
-	S8Slice path = s8slice_from_cstr(argv[1]);
-	const S8Slice f = os_open_file(path, OS_READ);
+    S8Slice path = s8slice_from_cstr(argv[1]);
+    const S8Slice f = os_open_file(path, OS_READ);
 
-	if (f.len == -1) {
-		fprintf(stderr, "could not open file %s: %s\n", path.data, strerror(errno));
-		exit(EXIT_FAILURE);
-	}
+    if (f.len == -1) {
+        fprintf(stderr, "could not open file %s: %s\n", path.data, strerror(errno));
+        exit(EXIT_FAILURE);
+    }
 
-	Parser p = parser_attach(f);
-	Token t = {0};
-	while (true) {
-		parser_discard(&p, isspace);
-		Token t = read_token(&p);
-		if (t.kind == TOKEN_IDENTIFIER) {
-			S8Slice s = t.identifier;
-			printf("{.len = %lld, .data = %.*s}\n", s.len, (int)s.len, s.data);
-		} else if (t.kind == TOKEN_INT) {
-			printf("%d\n", t.integer);
-		} else if (t.kind == TOKEN_STRING) {
-			S8Slice s = t.identifier;
-			printf("{.len = %lld, .data = %.*s}\n", s.len, (int)s.len, s.data);
-		} else if (t.kind == TOKEN_EOF) {
-			break;
-		}
-	}
+    Parser p = parser_attach(f);
+    Token t = {0};
+    while (true) {
+        parser_discard(&p, isspace_except_newline);
+        Token t = read_token(&p);
+        printf("%s\t", token_kind_str[t.kind]);
+        if (t.kind == TOKEN_ID) {
+            S8Slice s = t.identifier;
+            printf("<%.*s>\n", (int)s.len, s.data);
+        }
+        else if (t.kind == TOKEN_INT) {
+            printf("%d\n", t.integer);
+        }
+        else if (t.kind == TOKEN_STRING) {
+            S8Slice s = t.identifier;
+            printf("\"%.*s\"\n", (int)s.len, s.data);
+        }
+        else if (t.kind == TOKEN_EOF) {
+            break;
+        } else if (t.kind == TOKEN_UNDEFINED) {
+            printf("'%c'\n", t.undefined);
+        }
+        else {
+            printf("\n");
+        }
+    }
 
-	return EXIT_SUCCESS;
+    return EXIT_SUCCESS;
 }