diff --git a/headers/vmath.hpp/vmath_ext.hpp b/headers/vmath.hpp/vmath_ext.hpp
index 76e9d76..e13f97d 100644
--- a/headers/vmath.hpp/vmath_ext.hpp
+++ b/headers/vmath.hpp/vmath_ext.hpp
@@ -510,7 +510,7 @@ namespace vmath_hpp
 
     template < typename T, std::size_t Size >
     T angle(const vec<T, Size>& x, const vec<T, Size>& y) {
-        return acos(dot(x, y) * invsqrt(length2(x) * length2(y)));
+        return acos(dot(x, y) * rsqrt(length2(x) * length2(y)));
     }
 
     // rotate
diff --git a/headers/vmath.hpp/vmath_fun.hpp b/headers/vmath.hpp/vmath_fun.hpp
index 8baed1d..5e7e4b3 100644
--- a/headers/vmath.hpp/vmath_fun.hpp
+++ b/headers/vmath.hpp/vmath_fun.hpp
@@ -15,31 +15,94 @@
 namespace vmath_hpp
 {
     template < typename T >
-    constexpr T radians(T degrees) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr radians(T degrees) noexcept {
         return degrees * T(0.01745329251994329576923690768489);
     }
 
     template < typename T >
-    constexpr T degrees(T radians) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr degrees(T radians) noexcept {
         return radians * T(57.295779513082320876798154814105);
     }
 
-    using ::std::sin;
-    using ::std::cos;
-    using ::std::tan;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    sin(T x) noexcept {
+        return std::sin(x);
+    }
 
-    using ::std::asin;
-    using ::std::acos;
-    using ::std::atan;
-    using ::std::atan2;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    cos(T x) noexcept {
+        return std::cos(x);
+    }
 
-    using ::std::sinh;
-    using ::std::cosh;
-    using ::std::tanh;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    tan(T x) noexcept {
+        return std::tan(x);
+    }
 
-    using ::std::asinh;
-    using ::std::acosh;
-    using ::std::atanh;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    asin(T x) noexcept {
+        return std::asin(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    acos(T x) noexcept {
+        return std::acos(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    atan(T x) noexcept {
+        return std::atan(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    atan2(T y, T x) noexcept {
+        return std::atan2(y, x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    sinh(T x) noexcept {
+        return std::sinh(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    cosh(T x) noexcept {
+        return std::cosh(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    tanh(T x) noexcept {
+        return std::tanh(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    asinh(T x) noexcept {
+        return std::asinh(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    acosh(T x) noexcept {
+        return std::acosh(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    atanh(T x) noexcept {
+        return std::atanh(x);
+    }
 }
 
 //
@@ -48,15 +111,45 @@ namespace vmath_hpp
 
 namespace vmath_hpp
 {
-    using ::std::pow;
-    using ::std::exp;
-    using ::std::log;
-    using ::std::exp2;
-    using ::std::log2;
-    using ::std::sqrt;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    pow(T x, T y) noexcept {
+        return std::pow(x, y);
+    }
 
     template < typename T >
-    T invsqrt(T x) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    exp(T x) noexcept {
+        return std::exp(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    log(T x) noexcept {
+        return std::log(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    exp2(T x) noexcept {
+        return std::exp2(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    log2(T x) noexcept {
+        return std::log2(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    sqrt(T x) noexcept {
+        return std::sqrt(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    rsqrt(T x) noexcept {
         return T(1) / sqrt(x);
     }
 }
@@ -80,48 +173,92 @@ namespace vmath_hpp
     }
 
     template < typename T >
-    constexpr T sign(T x) noexcept {
+    std::enable_if_t<std::is_arithmetic_v<T>, T>
+    constexpr sign(T x) noexcept {
         return static_cast<T>((T(0) < x) - (x < T(0)));
     }
 
-    using ::std::floor;
-    using ::std::trunc;
-    using ::std::round;
-    using ::std::ceil;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    floor(T x) noexcept {
+        return std::floor(x);
+    }
 
     template < typename T >
-    T fract(T x) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    trunc(T x) noexcept {
+        return std::trunc(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    round(T x) noexcept {
+        return std::round(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    ceil(T x) noexcept {
+        return std::ceil(x);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    fract(T x) noexcept {
         return x - floor(x);
     }
 
-    using ::std::fmod;
-    using ::std::modf;
-
-    using ::std::min;
-    using ::std::max;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    fmod(T x, T y) noexcept {
+        return std::fmod(x, y);
+    }
 
     template < typename T >
-    constexpr T clamp(T x, T min_x, T max_x) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    modf(T x, T* y) noexcept {
+        return std::modf(x, y);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_arithmetic_v<T>, T>
+    constexpr min(T x, T y) noexcept {
+        return std::min(x, y);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_arithmetic_v<T>, T>
+    constexpr max(T x, T y) noexcept {
+        return std::max(x, y);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_arithmetic_v<T>, T>
+    constexpr clamp(T x, T min_x, T max_x) noexcept {
         return min(max(x, min_x), max_x);
     }
 
     template < typename T >
-    constexpr T saturate(T x) noexcept {
+    std::enable_if_t<std::is_arithmetic_v<T>, T>
+    constexpr saturate(T x) noexcept {
         return clamp(x, T(0), T(1));
     }
 
     template < typename T >
-    constexpr T lerp(T x, T y, T a) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr lerp(T x, T y, T a) noexcept {
         return x * (T(1) - a) + y * a;
     }
 
     template < typename T >
-    constexpr T step(T edge, T x) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr step(T edge, T x) noexcept {
         return x < edge ? T(0) : T(1);
     }
 
     template < typename T >
-    constexpr T smoothstep(T edge0, T edge1, T x) noexcept {
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    constexpr smoothstep(T edge0, T edge1, T x) noexcept {
         const T t = clamp((x - edge0) / (edge1 - edge0), T(0), T(1));
         return t * t * (T(3) - T(2) * t);
     }
@@ -129,16 +266,24 @@ namespace vmath_hpp
     using ::std::isnan;
     using ::std::isinf;
     using ::std::isfinite;
-    using ::std::isnormal;
 
     template < typename T >
-    bool issubnormal(T x) noexcept {
-        return std::fpclassify(x) == FP_SUBNORMAL;
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    fma(T x, T y, T z) noexcept {
+        return std::fma(x, y, z);
     }
 
-    using ::std::fma;
-    using ::std::frexp;
-    using ::std::ldexp;
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    frexp(T x, int* exp) noexcept {
+        return std::frexp(x, exp);
+    }
+
+    template < typename T >
+    std::enable_if_t<std::is_floating_point_v<T>, T>
+    ldexp(T x, int exp) noexcept {
+        return std::ldexp(x, exp);
+    }
 }
 
 //
@@ -174,7 +319,7 @@ namespace vmath_hpp
 
     template < typename T >
     T normalize(T x) noexcept {
-        return x * invsqrt(dot(x, x));
+        return x * rsqrt(dot(x, x));
     }
 
     template < typename T >
diff --git a/headers/vmath.hpp/vmath_fwd.hpp b/headers/vmath.hpp/vmath_fwd.hpp
index c9e2bad..01f8ea6 100644
--- a/headers/vmath.hpp/vmath_fwd.hpp
+++ b/headers/vmath.hpp/vmath_fwd.hpp
@@ -6,13 +6,11 @@
 
 #pragma once
 
-#include <cassert>
 #include <cmath>
 #include <cstddef>
 
 #include <algorithm>
 #include <functional>
-#include <iterator>
 #include <stdexcept>
 #include <type_traits>
 #include <utility>
@@ -45,6 +43,10 @@ namespace vmath_hpp
     using size2 = vec<std::size_t, 2>;
     using size3 = vec<std::size_t, 3>;
     using size4 = vec<std::size_t, 4>;
+
+    using ptrdiff2 = vec<std::ptrdiff_t, 2>;
+    using ptrdiff3 = vec<std::ptrdiff_t, 3>;
+    using ptrdiff4 = vec<std::ptrdiff_t, 4>;
 }
 
 namespace vmath_hpp
@@ -75,4 +77,8 @@ namespace vmath_hpp
     using size2x2 = mat<std::size_t, 2>;
     using size3x3 = mat<std::size_t, 3>;
     using size4x4 = mat<std::size_t, 4>;
+
+    using ptrdiff2x2 = mat<std::ptrdiff_t, 2>;
+    using ptrdiff3x3 = mat<std::ptrdiff_t, 3>;
+    using ptrdiff4x4 = mat<std::ptrdiff_t, 4>;
 }
diff --git a/headers/vmath.hpp/vmath_vec_fun.hpp b/headers/vmath.hpp/vmath_vec_fun.hpp
index 7700c13..6212191 100644
--- a/headers/vmath.hpp/vmath_vec_fun.hpp
+++ b/headers/vmath.hpp/vmath_vec_fun.hpp
@@ -370,8 +370,8 @@ namespace vmath_hpp
     }
 
     template < typename T, std::size_t Size >
-    vec<T, Size> invsqrt(const vec<T, Size>& xs) {
-        return map([](T x) { return invsqrt(x); }, xs);
+    vec<T, Size> rsqrt(const vec<T, Size>& xs) {
+        return map([](T x) { return rsqrt(x); }, xs);
     }
 }
 
@@ -529,16 +529,6 @@ namespace vmath_hpp
         return map([](T x) { return isfinite(x); }, xs);
     }
 
-    template < typename T, std::size_t Size >
-    vec<bool, Size> isnormal(const vec<T, Size>& xs) {
-        return map([](T x) { return isnormal(x); }, xs);
-    }
-
-    template < typename T, std::size_t Size >
-    vec<bool, Size> issubnormal(const vec<T, Size>& xs) {
-        return map([](T x) { return issubnormal(x); }, xs);
-    }
-
     template < typename T, std::size_t Size >
     vec<T, Size> fma(const vec<T, Size>& as, const vec<T, Size>& bs, const vec<T, Size>& cs) {
         return zip([](T a, T b, T c) { return fma(a, b, c); }, as, bs, cs);
@@ -611,7 +601,7 @@ namespace vmath_hpp
 
     template < typename T, std::size_t Size >
     vec<T, Size> normalize(const vec<T, Size>& xs) {
-        return xs * invsqrt(dot(xs, xs));
+        return xs * rsqrt(dot(xs, xs));
     }
 
     template < typename T, std::size_t Size >
diff --git a/untests/vmath_fun_tests.cpp b/untests/vmath_fun_tests.cpp
index c32ab7b..96c2769 100644
--- a/untests/vmath_fun_tests.cpp
+++ b/untests/vmath_fun_tests.cpp
@@ -47,7 +47,7 @@ TEST_CASE("vmath/fun") {
         (void)exp2(2.f);
         (void)log2(2.f);
         (void)sqrt(2.f);
-        (void)invsqrt(2.f);
+        (void)rsqrt(2.f);
     }
 
     SECTION("Common Functions") {
@@ -98,8 +98,6 @@ TEST_CASE("vmath/fun") {
         REQUIRE_FALSE(isnan(1.f));
         REQUIRE_FALSE(isinf(1.f));
         REQUIRE(isfinite(1.f));
-        REQUIRE(isnormal(1.f));
-        REQUIRE_FALSE(issubnormal(1.f));
 
         REQUIRE(fma(2.f, 3.f, 4.f) == approx(10.f));
 
diff --git a/untests/vmath_vec_fun_tests.cpp b/untests/vmath_vec_fun_tests.cpp
index 18584d4..19a574f 100644
--- a/untests/vmath_vec_fun_tests.cpp
+++ b/untests/vmath_vec_fun_tests.cpp
@@ -95,7 +95,7 @@ TEST_CASE("vmath/vec_fun") {
         (void)exp2(float2(1.f));
         (void)log2(float2(1.f));
         (void)sqrt(float2(1.f));
-        (void)invsqrt(float2(1.f));
+        (void)rsqrt(float2(1.f));
     }
 
     SECTION("Common Functions") {
@@ -144,8 +144,6 @@ TEST_CASE("vmath/vec_fun") {
         REQUIRE_FALSE(isnan(float2(1.f)).x);
         REQUIRE_FALSE(isinf(float2(1.f)).x);
         REQUIRE(isfinite(float2(1.f)).x);
-        REQUIRE(isnormal(float2(1.f)).x);
-        REQUIRE_FALSE(issubnormal(float2(1.f)).x);
 
         REQUIRE_FALSE(fma(float2(2.f), float2(3.f), float2(4.f)).x == Approx(12.f));