diff --git a/codon/runtime/re.cpp b/codon/runtime/re.cpp
index c401b176..751bf231 100644
--- a/codon/runtime/re.cpp
+++ b/codon/runtime/re.cpp
@@ -141,7 +141,7 @@ SEQ_FUNC Span *seq_re_match(Regex *re, seq_int_t anchor, seq_str_t s, seq_int_t
   auto *spans = (Span *)seq_alloc_atomic(num_groups * sizeof(Span));
   unsigned i = 0;
   for (const auto &it : groups) {
-    if (it.data() == NULL) {
+    if (it.data() == nullptr) {
       spans[i++] = {-1, -1};
     } else {
       spans[i++] = {static_cast<seq_int_t>(it.data() - s.str),
diff --git a/stdlib/re.codon b/stdlib/re.codon
index b72b610b..bfc27d6c 100644
--- a/stdlib/re.codon
+++ b/stdlib/re.codon
@@ -29,7 +29,7 @@ class Span:
         return not (self.start == -1 and self.end == -1)
 
 @C
-@nocapture
+@pure
 def seq_re_match(re: cobj,
                  anchor: int,
                  string: str,
@@ -61,13 +61,6 @@ def seq_re_group_name_to_index(re: cobj, name: str) -> int:
 def seq_re_group_index_to_name(re: cobj, index: int) -> str:
     pass
 
-@C
-@nocapture
-def seq_re_pattern_groupindex(re: cobj,
-                              names: Ptr[Ptr[str]],
-                              indices: Ptr[Ptr[int]]) -> int:
-    pass
-
 @C
 @pure
 def seq_re_pattern_error(re: cobj) -> str:
@@ -83,6 +76,7 @@ def seq_re_purge() -> void:
     pass
 
 @C
+@pure
 def seq_re_compile(pattern: str, flags: int) -> cobj:
     pass
 
@@ -134,13 +128,13 @@ def finditer(pattern: str, string: str, flags: int = 0):
 def findall(pattern: str, string: str, flags: int = 0):
     return compile(pattern, flags).findall(string)
 
-def split(pattern: str, string: str, maxsplit: int =0, flags: int = 0):
+def split(pattern: str, string: str, maxsplit: int = 0, flags: int = 0):
     return compile(pattern, flags).split(string, maxsplit)
 
-def sub(pattern: str, repl, string: str, count: int =0, flags: int = 0):
+def sub(pattern: str, repl, string: str, count: int = 0, flags: int = 0):
     return compile(pattern, flags).sub(repl, string, count)
 
-def subn(pattern: str, repl, string: str, count: int =0, flags: int = 0):
+def subn(pattern: str, repl, string: str, count: int = 0, flags: int = 0):
     return compile(pattern, flags).subn(repl, string, count)
 
 def escape(pattern: str):