diff --git a/src/libcore/bool.rs b/src/libcore/bool.rs
index 0fc869d1b41a93b0b8077bcc30ce0a12a375cf93..af4b752f4dd1a7e556168154eb94d1acf637ff30 100644
--- a/src/libcore/bool.rs
+++ b/src/libcore/bool.rs
@@ -123,7 +123,7 @@ fn all_values(blk: block(v: t)) {
 
 An u8 whose first bit is set if `if_true(v)` holds
 */
-fn to_bit(v: t) -> u8 { if v { 1u8 } else { 0u8 } }
+pure fn to_bit(v: t) -> u8 { if v { 1u8 } else { 0u8 } }
 
 // Local Variables:
 // mode: rust;
diff --git a/src/libcore/box.rs b/src/libcore/box.rs
index 6682fe17284ac429a2000635d04d02b418d8327f..23b5889bc6a4e5f6ce31574dec81e5841e47f716 100644
--- a/src/libcore/box.rs
+++ b/src/libcore/box.rs
@@ -10,7 +10,7 @@
 
 Determine if two shared boxes point to the same object
 */
-fn ptr_eq<T>(a: @T, b: @T) -> bool {
+pure fn ptr_eq<T>(a: @T, b: @T) -> bool {
     // FIXME: ptr::addr_of
     unsafe {
         let a_ptr: uint = unsafe::reinterpret_cast(a);
diff --git a/src/libcore/char.rs b/src/libcore/char.rs
index 5ff7681ae8ab484dc377d2f71541d5dcc24d283a..2648c8481dfa17134100188232cbde7aa2e3a8fa 100644
--- a/src/libcore/char.rs
+++ b/src/libcore/char.rs
@@ -122,7 +122,7 @@
  Convert a char to the corresponding digit. Returns none when the
  character is not a valid hexadecimal digit.
 */
-fn maybe_digit(c: char) -> option::t<u8> {
+pure fn maybe_digit(c: char) -> option::t<u8> {
     alt c {
       '0' to '9' { option::some(c as u8 - ('0' as u8)) }
       'a' to 'z' { option::some(c as u8 + 10u8 - ('a' as u8)) }
@@ -143,7 +143,7 @@ fn maybe_digit(c: char) -> option::t<u8> {
  Returns:
   -1 if a<b, 0 if a==b, +1 if a>b
 */
-fn cmp(a: char, b: char) -> int {
+pure fn cmp(a: char, b: char) -> int {
     ret  if b > a { -1 }
     else if b < a { 1 }
     else { 0 }
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 403cb47f47e645d608a2fe04f1ea27f89fbd888f..39e68a01519bff70c1c83cf9d5795a30a616e3dd 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -30,7 +30,7 @@
 
 Fails if the value equals `none`.
 */
-fn get<copy T>(opt: t<T>) -> T {
+pure fn get<copy T>(opt: t<T>) -> T {
     alt opt { some(x) { ret x; } none. { fail "option none"; } }
 }
 
@@ -61,7 +61,7 @@ fn map<T, U>(f: block(T) -> U, opt: t<T>) -> t<U> {
 
 Returns the contained value or a default
 */
-fn from_maybe<T>(def: T, opt: t<T>) -> T {
+pure fn from_maybe<T>(def: T, opt: t<T>) -> T {
     alt opt { some(x) { x } none. { def } }
 }
 
diff --git a/src/libcore/str.rs b/src/libcore/str.rs
index 8a532fcc75323437b5aabd007eefebbfdabeb8ba..802297223e9bce490dda0f670d91c9e45bff7119 100644
--- a/src/libcore/str.rs
+++ b/src/libcore/str.rs
@@ -26,14 +26,14 @@
 
 Bytewise string equality
 */
-fn eq(&&a: str, &&b: str) -> bool { a == b }
+pure fn eq(&&a: str, &&b: str) -> bool { a == b }
 
 /*
 Function: lteq
 
 Bytewise less than or equal
 */
-fn lteq(&&a: str, &&b: str) -> bool { a <= b }
+pure fn lteq(&&a: str, &&b: str) -> bool { a <= b }
 
 /*
 Function: hash
@@ -131,7 +131,7 @@ fn is_whitespace(s: str) -> bool {
 
 Returns the length in bytes of a string
 */
-fn byte_len(s: str) -> uint unsafe {
+pure fn byte_len(s: str) -> uint unsafe {
     let v: [u8] = unsafe::reinterpret_cast(s);
     let vlen = vec::len(v);
     unsafe::leak(v);
@@ -261,7 +261,7 @@ fn from_chars(chs: [char]) -> str {
 
 FIXME: What does this function do?
 */
-fn utf8_char_width(b: u8) -> uint {
+pure fn utf8_char_width(b: u8) -> uint {
     let byte: uint = b as uint;
     if byte < 128u { ret 1u; }
     if byte < 192u {
diff --git a/src/libcore/sys.rs b/src/libcore/sys.rs
index 3b4a3b8c64378eeae0c037f9c453d26018ffd0bf..9c8b097211173a63bb518885834d8e1117af8e9d 100644
--- a/src/libcore/sys.rs
+++ b/src/libcore/sys.rs
@@ -42,7 +42,7 @@ fn get_type_desc<T>() -> *type_desc {
 Get a string representing the platform-dependent last error
 */
 fn last_os_error() -> str {
-    ret rustrt::last_os_error();
+    rustrt::last_os_error()
 }
 
 /*
diff --git a/src/libcore/vec.rs b/src/libcore/vec.rs
index d8f89b3b27bc943407e23048c94832c913faa933..d056eb8d04dcc048843de134b4a3e7aa33970741 100644
--- a/src/libcore/vec.rs
+++ b/src/libcore/vec.rs
@@ -181,7 +181,7 @@ fn from_mut<copy T>(v: [mutable T]) -> [T] {
 Predicates:
 <is_not_empty> (v)
 */
-fn head<copy T>(v: [const T]) : is_not_empty(v) -> T { ret v[0]; }
+pure fn head<copy T>(v: [const T]) : is_not_empty(v) -> T { ret v[0]; }
 
 /*
 Function: tail
@@ -221,7 +221,7 @@ fn init<copy T>(v: [const T]) -> [T] {
 An option containing the last element of `v` if `v` is not empty, or
 none if `v` is empty.
 */
-fn last<copy T>(v: [const T]) -> option::t<T> {
+pure fn last<copy T>(v: [const T]) -> option::t<T> {
     if len(v) == 0u { ret none; }
     ret some(v[len(v) - 1u]);
 }
@@ -234,7 +234,7 @@ fn last<copy T>(v: [const T]) -> option::t<T> {
 Predicates:
 <is_not_empty> (v)
 */
-fn last_total<copy T>(v: [const T]) : is_not_empty(v) -> T {
+pure fn last_total<copy T>(v: [const T]) : is_not_empty(v) -> T {
     ret v[len(v) - 1u];
 }