diff --git a/Cargo.lock b/Cargo.lock
index 5cda058..8b79dea 100755
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,31 @@
 # It is not intended for manual editing.
 version = 4
 
+[[package]]
+name = "foldhash"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f81ec6369c545a7d40e4589b5597581fa1c441fe1cce96dd1de43159910a36a2"
+
+[[package]]
+name = "hashbrown"
+version = "0.15.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf151400ff0baff5465007dd2f3e717f3fe502074ca563069ce3a6629d07b289"
+dependencies = [
+ "foldhash",
+ "rustc-std-workspace-alloc",
+]
+
 [[package]]
 name = "rlisp"
 version = "0.1.0"
+dependencies = [
+ "hashbrown",
+]
+
+[[package]]
+name = "rustc-std-workspace-alloc"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f9d441c3b2ebf55cebf796bfdc265d67fa09db17b7bb6bd4be75c509e1e8fec3"
diff --git a/Cargo.toml b/Cargo.toml
index 14b5d43..11d78bd 100755
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,3 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+hashbrown = { version = "0.15", default-features = false, features = [
+ "alloc",
+ "default-hasher",
+] }
diff --git a/src/lib/mod.rs b/src/lib/mod.rs
index ff7ced6..c1e848e 100755
--- a/src/lib/mod.rs
+++ b/src/lib/mod.rs
@@ -1,7 +1,12 @@
-use core::num::ParseFloatError;
-use std::fmt;
+use core::fmt;
+
+use core::num::ParseFloatError;
+// use std::hash::DefaultHasher;
+
+extern crate alloc;
+
+pub use hashbrown::hash_map::HashMap;
 
-pub use std::collections::HashMap;
 pub use std::io::Write;
 pub use std::rc::Rc;
 
diff --git a/src/main.rs b/src/main.rs
index 266225b..ed72326 100755
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,5 +1,8 @@
 #![feature(slice_take)]
 #![allow(special_module_name)]
+#![feature(build_hasher_default_const_new)]
+// #![no_std]
+
 use std::io;
 use std::io::Write;