diff --git a/runtime/src/capi.rs b/runtime/src/capi.rs
index 3884bb8..45b16cc 100644
--- a/runtime/src/capi.rs
+++ b/runtime/src/capi.rs
@@ -11,3 +11,9 @@ pub extern "C" fn scm_from_utf8_string (
     let bytes = unsafe { slice::from_raw_parts (ptr, len) };
     scm::make_string (str::from_utf8 (bytes).unwrap ())
 }
+
+#[unsafe(no_mangle)]
+pub extern "C" fn scm_hash (ptr : *const u8, len : usize) -> u64 {
+    let bytes = unsafe { slice::from_raw_parts (ptr, len) };
+    crate::obarray::hash (str::from_utf8 (bytes).unwrap ())
+}
diff --git a/runtime/src/obarray.rs b/runtime/src/obarray.rs
index 30dd04f..04a8886 100644
--- a/runtime/src/obarray.rs
+++ b/runtime/src/obarray.rs
@@ -3,8 +3,24 @@ use crate::scm::scm_bits;
 use crate::scm;
 
 mod fnv1a;
+use fnv1a::{FNV1a, SymbolHash};
 
-pub struct Obarray (HashMap <String, scm_bits>);
+pub struct Obarray (HashMap <String, scm_bits, SymbolHash>);
 
-pub fn hash () {
+pub const fn new () -> Obarray {
+    Obarray (HashMap::with_hasher (SymbolHash ()))
 }
+
+pub fn hash (s : &str) -> u64 {
+    let mut a : FNV1a = Default::default ();
+    a.write (s.as_bytes ());
+    return a.finish ()
+}
+
+impl Obarray {
+    pub fn insert (&mut self) {
+
+    }
+}
+
+pub static symbols : Obarray = new ();
diff --git a/runtime/src/obarray/fnv1a.rs b/runtime/src/obarray/fnv1a.rs
index 3d95577..9c0e015 100644
--- a/runtime/src/obarray/fnv1a.rs
+++ b/runtime/src/obarray/fnv1a.rs
@@ -1,7 +1,13 @@
 use std::{collections::HashMap, hash::{BuildHasher, Hasher}};
 
 pub struct FNV1a (u64);
-pub struct SymbolHash;
+pub struct SymbolHash ();
+
+impl Default for FNV1a {
+    fn default () -> Self {
+        FNV1a (offset_basis)
+    }
+}
 
 impl Hasher for FNV1a {
     fn finish (&self) -> u64 {
@@ -24,5 +30,5 @@ impl BuildHasher for SymbolHash {
     }
 }
 
-const offset_basis : u64 = 0xcbf29ce484222325;
-const prime : u64 = 0x100000001b3;
+pub const offset_basis : u64 = 0xcbf29ce484222325;
+pub const prime : u64 = 0x100000001b3;
diff --git a/runtime/src/scm.rs b/runtime/src/scm.rs
index 41d5c6e..31abd45 100644
--- a/runtime/src/scm.rs
+++ b/runtime/src/scm.rs
@@ -9,7 +9,7 @@ pub type scm_bits = u64;
 
 pub const tc2_int      : u64 = 2;
 pub const tc3_cons     : u64 = 0;
-pub const tc7_weak_set : u64 = 0x55;
+pub const tc7_obarray  : u64 = 0x55;
 pub const tc7_symbol   : u64 = 0x05;
 pub const tc7_string   : u64 = 0x15;