diff --git a/.gitignore b/.gitignore
index 82bdbcb..fc3f878 100644
--- a/.gitignore
+++ b/.gitignore
@@ -45,3 +45,4 @@ misc/kf/kf
 *.bin
 blue-pill/*/*.d
 core
+bitwise/ion/ion
diff --git a/bitwise/ion/Makefile b/bitwise/ion/Makefile
index d5410d6..1c0c449 100644
--- a/bitwise/ion/Makefile
+++ b/bitwise/ion/Makefile
@@ -1,6 +1,6 @@
 TARGET :=	ion
 OBJS :=		$(TARGET).o
-CFLAGS :=	-g -std=c99
+CFLAGS :=	-g -std=c99 -Wall -Werror
 
 all: $(TARGET)
 
diff --git a/bitwise/ion/ion.c b/bitwise/ion/ion.c
index f179107..3fa915f 100644
--- a/bitwise/ion/ion.c
+++ b/bitwise/ion/ion.c
@@ -1,10 +1,11 @@
 #include <assert.h>
 #include <stdbool.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
-#define MAX(a, b) a < b ? b : a
+#define MAX(a, b) ((a) < (b) ? (b) : (a))
 
 // stretchy buffers
 typedef struct _BufHeader {
@@ -13,54 +14,91 @@ typedef struct _BufHeader {
 	char	buf[0]; // C99
 } BufHeader;
 
-#define buf__hdr(b)	(BufHeader *)((char *)buf - offsetof(BufHeader, buf))
-#define buf_fits(b, n)	((buf_len(b) + n) <= buf_cap(b))
-#define buf__fit(b, n) (buf__fits(b, n) ? 0 : (b) = (buf_grow(b, 2*buf_cap(b), sizeof(*b))))
+void *buf__grow(const void *, size_t, size_t);
+#define buf__hdr(b)	((BufHeader *)((char *)(b) - offsetof(BufHeader, buf)))
+#define buf__fits(b, n)	((buf_len(b) + n) <= buf_cap(b))
+#define buf__fit(b, n) (buf__fits(b, n) ? 0 : ((b) = (buf__grow((b), buf_len(b) + (n), sizeof(*(b))))))
 
 #define buf_len(b)	((b) ? buf__hdr(b)->len : 0)
 #define buf_cap(b)	((b) ? buf__hdr(b)->cap : 0)
-#define buf_push(b, x)	(buf__fit((b), 1), (b)[buf_len(b)++] = (x))
+#define buf_push(b, x)	(buf__fit((b), 1), (b)[buf_len((b))] = (x), buf__hdr((b))->len++)
+#define buf_free(b)	((b) ? free(buf__hdr((b))) : 0)
+
+#define prlu(m, v)	(printf("%s: %lu\n", m, (unsigned long)(v)))
 
 void *
 buf__grow(const void *buf, size_t nlen, size_t esize)
 {
-	size_t ncap = MAX(1 + 2*buf_cap(buf), new_len);
+	size_t ncap = MAX(1 + 2*buf_cap(buf), nlen);
 	assert(nlen <= ncap);
-	size_t nsize = ncap * esize;
-	BufHdr *nhdr;
+	size_t nsize = offsetof(BufHeader, buf) + ncap * esize;
+	BufHeader *nhdr;
 	
 	if (buf) {
-		nhdr = realloc(buf__hdr(buf), nsize)
+		nhdr = realloc(buf__hdr(buf), nsize);
 	}
 	else {
-		nhdr = malloc(new_size)
+		nhdr = malloc(nsize);
 		nhdr->len = 0;
 	}
 
-	nhdr.cap = ncap;
-	return nhdr;
+	nhdr->cap = ncap;
+	return nhdr->buf;
+}
+
+static void
+buf_test(void)
+{
+	int	*stretchy = NULL;
+	for (int i = 0; i < 1024; i++) {
+		buf_push(stretchy, i);
+	}
+
+	for (int i = 0; i < buf_len(stretchy); i++) {
+		assert(stretchy[i] == i);
+	}
+
+	buf_free(stretchy);
+	printf("OK\n");
+}
+typedef enum TokenKind {
+	TOKEN_INT,
+	TOKEN_NAME,
+	// ...
+} TokenKind;
+
+typedef struct Token {
+	TokenKind	kind;
+	// ...
+} Token;
+
+Token token;
+void next_token(void) {
+	switch (*stream) {
+	case '0':
+	case '1':
+	case '2':
+	case '3':
+	case '4':
+	case '5':
+	case '6':
+	case '7':
+	case '8':
+	case '9':
+		while (isdigit(*stream)) {
+			stream++;
+		}
+		token.kind = TOKEN_INT;
+		break;
+	default:
+		token.kind = *stream;
+		break;
+	}
 }
 
 int
 main(int argc, char *argv[])
 {
-	int	*buf = NULL;
-	buf_push(buf, 47); // std::vector::push_back
-	// now buf actually points to a buffer
-	buf_push(buf, 1234);
-
-	printf("buf length: %lu / cap: %lu\n",
-		(unsigned long)buf_len(buf),
-		(unsigned long)buf_cap(buf));
-	for (int i = 0; i < buf_len(buf); i++) {
-		printf("%d\n", buf[i]);
-	}
-
-	for (int i = 0; i < 1024; i++) {
-		buf_push(buf, i+1);
-	}
-	printf("buf length: %lu / cap: %lu\n", buf_len(buf), buf_cap(buf));
-
-	buf_free(buf);
+	buf_test();
 	return 0;
 }
\ No newline at end of file
diff --git a/bitwise/ion/notes.txt b/bitwise/ion/notes.txt
index 30584a2..87f1038 100644
--- a/bitwise/ion/notes.txt
+++ b/bitwise/ion/notes.txt
@@ -8,4 +8,13 @@ NOTES
 
 stretch buffers:
 + dynamically growable arrays such that with a few pitfalls but is easy to generate
-+ invented by stb?
\ No newline at end of file
++ invented by stb?
+
+
+2018-03-22 (day 2)
+------------------
++ lexing: char stream to token stream
+  + ex. '1234 (x+y)' translates to '1234' '(' 'x' '+' 'y' ')'
+  + no semantics yet
+  + simple hand-written approach
+  + mark: 1:06:11
\ No newline at end of file