diff --git a/arch/build.ninja b/arch/build.ninja
index fce2838..824efa4 100644
--- a/arch/build.ninja
+++ b/arch/build.ninja
@@ -5,9 +5,10 @@ rule archive
   command = ar rcs $out $in
 
 build abs.o: gas x64/linux/math/abs.S
+build log.o: gas x64/linux/math/log.S
 build cmp.o: gas x64/linux/memory/cmp.S
 build fill.o: gas x64/linux/memory/fill.S
 build copy.o: gas x64/linux/memory/copy.S
 build syscall.o: gas x64/linux/syscall.S
 
-build tanya.a: archive syscall.o copy.o fill.o cmp.o abs.o
+build tanya.a: archive syscall.o copy.o fill.o cmp.o log.o abs.o
diff --git a/arch/x64/linux/math/log.S b/arch/x64/linux/math/log.S
new file mode 100644
index 0000000..7f23703
--- /dev/null
+++ b/arch/x64/linux/math/log.S
@@ -0,0 +1,48 @@
+	.text
+
+
+// logl.
+	.globl _D5tanya4math8nbtheory2lnFNaNbNiNfeZe
+	.type _D5tanya4math8nbtheory2lnFNaNbNiNfeZe, @function
+
+_D5tanya4math8nbtheory2lnFNaNbNiNfeZe:
+	fldln2 // Put lb(e) onto the FPU stack
+	fldt 8(%rsp) // Put the argument onto the FPU stack
+	fyl2x // %st1 * lb(%st0)
+	ret
+
+
+// log.
+	.globl _D5tanya4math8nbtheory2lnFNaNbNiNfdZd
+	.type _D5tanya4math8nbtheory2lnFNaNbNiNfdZd, @function
+
+_D5tanya4math8nbtheory2lnFNaNbNiNfdZd:
+	movsd %xmm0, -8(%rsp) // Put the argument onto the stack
+
+	fldln2 // Put lb(e) onto the FPU stack
+	fldl -8(%rsp) // Put a double onto the FPU stack
+	fyl2x // %st1 * lb(%st0)
+
+	 // The result is on the FPU stack, but returned in %xmm0
+	fstpl -8(%rsp)
+	movsd -8(%rsp), %xmm0
+
+	ret
+
+
+// logf.
+	.globl _D5tanya4math8nbtheory2lnFNaNbNiNffZf
+	.type _D5tanya4math8nbtheory2lnFNaNbNiNffZf, @function
+
+_D5tanya4math8nbtheory2lnFNaNbNiNffZf:
+	movss %xmm0, -4(%rsp) // Put the argument onto the stack
+
+	fldln2 // Put lb(e) onto the FPU stack
+	flds -4(%rsp) // Put a float onto the FPU stack
+	fyl2x // %st1 * lb(%st0)
+
+	 // The result is on the FPU stack, but returned in %xmm0
+	fstps -4(%rsp)
+	movss -4(%rsp), %xmm0
+
+	ret
diff --git a/source/tanya/container/string.d b/source/tanya/container/string.d
index a89fe0c..b0bbeec 100644
--- a/source/tanya/container/string.d
+++ b/source/tanya/container/string.d
@@ -35,6 +35,7 @@ import tanya.memory;
 import tanya.meta.trait;
 import tanya.meta.transform;
 import tanya.range.array;
+import tanya.range.primitive;
 
 /**
  * Thrown on encoding errors.
@@ -352,9 +353,9 @@ struct String
      * Precondition: $(D_INLINECODE allocator is null).
      */
     this(S)(const S str, shared Allocator allocator = defaultAllocator)
-    if (!std.range.isInfinite!S
-     && std.range.isInputRange!S
-     && isSomeChar!(std.range.ElementEncodingType!S))
+    if (!isInfinite!S
+     && isInputRange!S
+     && isSomeChar!(ElementType!S))
     {
         this(allocator);
         insertBack(str);
@@ -667,12 +668,12 @@ struct String
      * Throws: $(D_PSYMBOL UTFException).
      */
     size_t insertBack(R)(R str) @trusted
-    if (!std.range.isInfinite!R
-     && std.range.isInputRange!R
-     && is(Unqual!(std.range.ElementEncodingType!R) == char))
+    if (!isInfinite!R
+     && isInputRange!R
+     && is(Unqual!(ElementType!R) == char))
     {
         size_t size;
-        static if (std.range.hasLength!R || isNarrowString!R)
+        static if (hasLength!R || isNarrowString!R)
         {
             size = str.length + length;
             reserve(size);
@@ -731,11 +732,11 @@ struct String
 
     /// ditto
     size_t insertBack(R)(R str) @trusted
-    if (!std.range.isInfinite!R
-     && std.range.isInputRange!R
-     && is(Unqual!(std.range.ElementEncodingType!R) == wchar))
+    if (!isInfinite!R
+     && isInputRange!R
+     && is(Unqual!(ElementType!R) == wchar))
     {
-        static if (std.range.hasLength!R || isNarrowString!R)
+        static if (hasLength!R || isNarrowString!R)
         {
             reserve(length + str.length * wchar.sizeof);
         }
@@ -797,11 +798,11 @@ struct String
 
     /// ditto
     size_t insertBack(R)(R str) @trusted
-    if (!std.range.isInfinite!R
-     && std.range.isInputRange!R
-     && is(Unqual!(std.range.ElementEncodingType!R) == dchar))
+    if (!isInfinite!R
+     && isInputRange!R
+     && is(Unqual!(ElementType!R) == dchar))
     {
-        static if (std.range.hasLength!R || isSomeString!R)
+        static if (hasLength!R || isSomeString!R)
         {
             reserve(length + str.length * 4);
         }
@@ -1268,9 +1269,9 @@ struct String
      * Throws: $(D_PSYMBOL UTFException).
      */
     ref String opAssign(S)(S that) nothrow
-    if (!std.range.isInfinite!S
-     && std.range.isInputRange!S
-     && isSomeChar!(std.range.ElementEncodingType!S))
+    if (!isInfinite!S
+     && isInputRange!S
+     && isSomeChar!(ElementType!S))
     {
         this.length_ = 0;
         insertBack(that);
@@ -1531,9 +1532,9 @@ struct String
      * Precondition: $(D_PARAM r) refers to a region of $(D_KEYWORD this).
      */
     size_t insertAfter(T, R)(R r, T el) @trusted
-    if ((isSomeChar!T || (!std.range.isInfinite!T
-     && std.range.isInputRange!T
-     && isSomeChar!(std.range.ElementEncodingType!T)))
+    if ((isSomeChar!T || (!isInfinite!T
+     && isInputRange!T
+     && isSomeChar!(ElementType!T)))
      && (is(R == ByCodeUnit!char) || is(R == ByCodePoint!char)))
     in
     {
@@ -1564,9 +1565,9 @@ struct String
 
     ///
     size_t insertBefore(T, R)(R r, T el) @trusted
-    if ((isSomeChar!T || (!std.range.isInfinite!T
-     && std.range.isInputRange!T
-     && isSomeChar!(std.range.ElementEncodingType!T)))
+    if ((isSomeChar!T || (!isInfinite!T
+     && isInputRange!T
+     && isSomeChar!(ElementType!T)))
      && (is(R == ByCodeUnit!char) || is(R == ByCodePoint!char)))
     in
     {
diff --git a/source/tanya/math/nbtheory.d b/source/tanya/math/nbtheory.d
index 6be04b9..4c94550 100644
--- a/source/tanya/math/nbtheory.d
+++ b/source/tanya/math/nbtheory.d
@@ -17,6 +17,15 @@ module tanya.math.nbtheory;
 import tanya.math.mp;
 import tanya.meta.trait;
 
+version (TanyaNative)
+{
+}
+else
+{
+    import core.math : fabs;
+    import std.math : log;
+}
+
 /**
  * Calculates the absolute value of a number.
  *
@@ -57,21 +66,19 @@ version (D_Ddoc)
     I abs(I)(I x)
     if (isFloatingPoint!I);
 }
-else version (TanyaPhobos)
+else version (TanyaNative)
+{
+    extern I abs(I)(I number) pure nothrow @safe @nogc
+    if (isFloatingPoint!I);
+}
+else
 {
-    import core.math;
-
     I abs(I)(I x)
     if (isFloatingPoint!I)
     {
         return fabs(cast(real) x);
     }
 }
-else
-{
-    extern I abs(I)(I number) pure nothrow @safe @nogc
-    if (isFloatingPoint!I);
-}
 
 ///
 pure nothrow @safe @nogc unittest
@@ -103,3 +110,56 @@ I abs(I : Integer)(I x)
     x.sign = Sign.positive;
     return x;
 }
+
+version (D_Ddoc)
+{
+    /**
+     * Calculates natural logarithm of $(D_PARAM x).
+     *
+     * Params:
+     *  x = Argument.
+     *
+     * Returns: Natural logarithm of $(D_PARAM x).
+     */
+    float ln(float x) pure nothrow @safe @nogc;
+    /// ditto
+    double ln(double x) pure nothrow @safe @nogc;
+    /// ditto
+    real ln(real x) pure nothrow @safe @nogc;
+}
+else version (TanyaNative)
+{
+    extern float ln(float x) pure nothrow @safe @nogc;
+    extern double ln(double x) pure nothrow @safe @nogc;
+    extern real ln(real x) pure nothrow @safe @nogc;
+}
+else
+{
+    float ln(float x) pure nothrow @safe @nogc
+    {
+        return log(x);
+    }
+    double ln(double x) pure nothrow @safe @nogc
+    {
+        return log(x);
+    }
+    alias ln = log;
+}
+
+///
+pure nothrow @safe @nogc unittest
+{
+    import tanya.math;
+
+    assert(isNaN(ln(-7.389f)));
+    assert(isNaN(ln(-7.389)));
+    assert(isNaN(ln(-7.389L)));
+
+    assert(isInfinity(ln(0.0f)));
+    assert(isInfinity(ln(0.0)));
+    assert(isInfinity(ln(0.0L)));
+
+    assert(ln(1.0f) == 0.0f);
+    assert(ln(1.0) == 0.0);
+    assert(ln(1.0L) == 0.0L);
+}