diff --git a/sample-code/hex.cl b/sample-code/hex.cl
index 64bddf3..95db8c5 100644
--- a/sample-code/hex.cl
+++ b/sample-code/hex.cl
@@ -1,26 +1,39 @@
 //! Formats numbers in hexadecimal, octal, or binary
 mod math;
 
-// TODO: casting and/or conversion
-const HEX_LUT: [char; 16] = [
-    '0', '1', '2', '3', //
-    '4', '5', '6', '7', //
-    '8', '9', 'a', 'b', //
-    'c', 'd', 'e', 'f', //
-];
+fn as_digit(n: u32) -> char {
+    (if n > 9 {
+        n - 10 + ('a' as u32)
+    } else {
+        n + ('0' as u32)
+    }) as char
+}
+
+pub fn radix(n: i64, radix: i64) {
+    fn r_str_radix(n: i64, radix: i64) {
+        if n != 0 {
+            r_str_radix(n / radix, radix) + as_digit(n % radix)
+        } else ""
+    }
+    if n == 0 {
+        "0"
+    } else if n < 0 {
+        // TODO: breaks at i64::MIN
+        "-" + r_str_radix(-n, radix)
+    } else r_str_radix(n, radix)
+}
 
 pub fn hex(n: u64) {
     let out = "0x";
     for xd in min(count_leading_zeroes(n) / 4, 15)..16 {
-        out += HEX_LUT[(n >> (15 - xd) * 4) & 0xf]
+        out += as_digit((n >> (15 - xd) * 4) & 0xf)
     }
     out
 }
-
 pub fn oct(n: u64) {
     let out = "0o";
     for xd in min((count_leading_zeroes(n) + 2) / 3, 21)..22 {
-        out += HEX_LUT[(n >> max(63 - (3 * xd), 0)) & 7]
+        out += as_digit((n >> max(63 - (3 * xd), 0)) & 7)
     }
     out
 }
@@ -28,7 +41,7 @@ pub fn oct(n: u64) {
 pub fn bin(n: u64) {
     let out = "0b";
     for xd in min(count_leading_zeroes(n), 63)..64 {
-        out += HEX_LUT[(n >> 63 - xd) & 1]
+        out += as_digit((n >> 63 - xd) & 1)
     }
     out
 }