diff --git a/Cargo.toml b/Cargo.toml
index fae83a04..f586d1f3 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,5 +16,4 @@ include = [
 
 [features]
 debug_msgs = []
-no-std = []
-stdlib = []
\ No newline at end of file
+no_stdlib = []
\ No newline at end of file
diff --git a/README.md b/README.md
index 35a5acbc..f0ab4f1a 100644
--- a/README.md
+++ b/README.md
@@ -33,6 +33,16 @@ to use the latest version.
 
 Beware that in order to use pre-releases (alpha and beta) you need to specify the exact version in your `Cargo.toml`.
 
+## Optional Features
+
+### `debug_msgs`
+
+Print debug messages to stdout (using `println!`) related to function registrations and function calls.
+
+### `no_stdlib`
+
+Exclude the standard library of utility functions in the build, and only include the minimum necessary functionalities.
+
 ## Related
 
 Other cool projects to check out:
@@ -601,7 +611,7 @@ println!(result);   // prints "Runtime error: 42 is too large! (line 5, position
 
 You can create arrays of values, and then access them with numeric indices.
 
-The following standard functions operate on arrays:
+The following functions (defined in the standard library but excluded if you use the `no_stdlib` feature) operate on arrays:
 
 * `push` - inserts an element at the end
 * `pop` - removes the last element and returns it (() if empty)
@@ -699,7 +709,7 @@ let x = 0o777;          // i64 in oct
 let x = 0b1010_1111;    // i64 in binary
 ```
 
-Conversion functions:
+Conversion functions (defined in the standard library but excluded if you use the `no_stdlib` feature):
 
 * `to_int` - converts an `f32` or `f64` to `i64`
 * `to_float` - converts an integer type to `f64`
@@ -714,7 +724,7 @@ let last = "Davis";
 let full_name = name + " " + middle_initial + ". " + last;
 full_name == "Bob C. Davis";
 
-// String building with different types
+// String building with different types (not available if 'no_stdlib' features is used)
 let age = 42;
 let record = full_name + ": age " + age;
 record == "Bob C. Davis: age 42";
@@ -738,7 +748,7 @@ record[4] = '\x58'; // 0x58 = 'X'
 record == "Bob X. Davis: age 42 ❤\n";
 ```
 
-The following standard functions operate on strings:
+The following standard functions (defined in the standard library but excluded if you use the `no_stdlib` feature) operate on strings:
 
 * `len` - returns the number of characters (not number of bytes) in the string
 * `pad` - pads the string with an character until a specified number of characters
diff --git a/src/builtin.rs b/src/builtin.rs
index 4e8810c4..ba175ea0 100644
--- a/src/builtin.rs
+++ b/src/builtin.rs
@@ -4,9 +4,6 @@ use crate::fn_register::RegisterFn;
 use std::fmt::{Debug, Display};
 use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Neg, Range, Rem, Shl, Shr, Sub};
 
-#[cfg(not(feature = "no-std"))]
-use crate::fn_register::RegisterDynamicFn;
-
 macro_rules! reg_op {
     ($self:expr, $x:expr, $op:expr, $( $y:ty ),*) => (
         $(
@@ -39,7 +36,7 @@ macro_rules! reg_func1 {
     )
 }
 
-#[cfg(any(not(feature = "no-std"), feature = "stdlib"))]
+#[cfg(not(feature = "no_stdlib"))]
 macro_rules! reg_func2x {
     ($self:expr, $x:expr, $op:expr, $v:ty, $r:ty, $( $y:ty ),*) => (
         $(
@@ -48,7 +45,7 @@ macro_rules! reg_func2x {
     )
 }
 
-#[cfg(any(not(feature = "no-std"), feature = "stdlib"))]
+#[cfg(not(feature = "no_stdlib"))]
 macro_rules! reg_func2y {
     ($self:expr, $x:expr, $op:expr, $v:ty, $r:ty, $( $y:ty ),*) => (
         $(
@@ -57,7 +54,7 @@ macro_rules! reg_func2y {
     )
 }
 
-#[cfg(any(not(feature = "no-std"), feature = "stdlib"))]
+#[cfg(not(feature = "no_stdlib"))]
 macro_rules! reg_func3 {
     ($self:expr, $x:expr, $op:expr, $v:ty, $w:ty, $r:ty, $( $y:ty ),*) => (
         $(
@@ -111,9 +108,6 @@ impl Engine<'_> {
         fn not(x: bool) -> bool {
             !x
         }
-        fn concat(x: String, y: String) -> String {
-            x + &y
-        }
         fn binary_and<T: BitAnd>(x: T, y: T) -> <T as BitAnd>::Output {
             x & y
         }
@@ -141,9 +135,6 @@ impl Engine<'_> {
         fn pow_f64_i64(x: f64, y: i64) -> f64 {
             x.powi(y as i32)
         }
-        fn unit_eq(_a: (), _b: ()) -> bool {
-            true
-        }
 
         reg_op!(self, "+", add, i8, u8, i16, u16, i32, i64, u32, u64, f32, f64);
         reg_op!(self, "-", sub, i8, u8, i16, u16, i32, i64, u32, u64, f32, f64);
@@ -179,8 +170,8 @@ impl Engine<'_> {
         reg_un!(self, "-", neg, i8, i16, i32, i64, f32, f64);
         reg_un!(self, "!", not, bool);
 
-        self.register_fn("+", concat);
-        self.register_fn("==", unit_eq);
+        self.register_fn("+", |x: String, y: String| x + &y); // String + String
+        self.register_fn("==", |_: (), _: ()| true); // () == ()
 
         // Register print and debug
         fn print_debug<T: Debug>(x: T) -> String {
@@ -221,8 +212,10 @@ impl Engine<'_> {
     }
 
     /// Register the built-in library.
-    #[cfg(any(not(feature = "no-std"), feature = "stdlib"))]
+    #[cfg(not(feature = "no_stdlib"))]
     pub(crate) fn register_stdlib(&mut self) {
+        use crate::fn_register::RegisterDynamicFn;
+
         // Register conversion functions
         self.register_fn("to_float", |x: i8| x as f64);
         self.register_fn("to_float", |x: u8| x as f64);
diff --git a/src/engine.rs b/src/engine.rs
index 60e38b08..813a335b 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -751,19 +751,19 @@ impl Engine<'_> {
 
         engine.register_core_lib();
 
-        #[cfg(any(not(feature = "no-std"), feature = "stdlib"))]
-        engine.register_stdlib(); // Register the standard library when not no-std or stdlib is set
+        #[cfg(not(feature = "no_stdlib"))]
+        engine.register_stdlib(); // Register the standard library when no_stdlib is not set
 
         engine
     }
 }
 
 /// Print/debug to stdout
-#[cfg(not(feature = "no-std"))]
+#[cfg(not(feature = "no_stdlib"))]
 fn default_print(s: &str) {
     println!("{}", s);
 }
 
 /// No-op
-#[cfg(feature = "no-std")]
+#[cfg(feature = "no_stdlib")]
 fn default_print(_: &str) {}