From c0639c609a78e9208b83a912e32f8dd0e8638e21 Mon Sep 17 00:00:00 2001
From: Kat Richey <thedarkqueenaeris@zoho.com>
Date: Thu, 27 Oct 2022 08:57:08 -0500
Subject: [PATCH] Wow, maths functions!

---
 math/log.c  | 21 +++++++++++++++++++++
 math/pow.c  |  5 +++++
 math/sqrt.c | 26 ++++++++++++++++++++++++++
 3 files changed, 52 insertions(+)
 create mode 100644 math/log.c
 create mode 100644 math/pow.c
 create mode 100644 math/sqrt.c

diff --git a/math/log.c b/math/log.c
new file mode 100644
index 0000000..a0a0c15
--- /dev/null
+++ b/math/log.c
@@ -0,0 +1,21 @@
+#include <math.h>
+
+double _agm(double x, double y) {
+  double a = x;
+  double g = y;
+  double temp;
+
+  for(int i = 0; i < 15; i++) {
+    temp = 0.5 * (a + g);
+    g = sqrt(a * g);
+    a = temp;
+  }
+
+  return a;
+}
+
+double log(double x) {
+  double s = x * exp2(24);
+  double nat_log = (M_PI / (2 * _agm(1, 4/s))) - (24 * M_LN2);
+  return nat_log;
+}
\ No newline at end of file
diff --git a/math/pow.c b/math/pow.c
new file mode 100644
index 0000000..9c88a26
--- /dev/null
+++ b/math/pow.c
@@ -0,0 +1,5 @@
+#include <math.h>
+
+double pow(double x, double y) {
+  return exp(y * log(x));
+}
\ No newline at end of file
diff --git a/math/sqrt.c b/math/sqrt.c
new file mode 100644
index 0000000..9d2b077
--- /dev/null
+++ b/math/sqrt.c
@@ -0,0 +1,26 @@
+#include <math.h>
+
+typedef union {
+  double d;
+  struct {
+    unsigned long int mantissa : 52;
+    unsigned int exponent : 11;
+    unsigned int sign_bit : 1;
+  } parts;
+} _dbl_cast;
+
+double sqrt(double x) {
+  _dbl_cast S = { .d = x };
+  double estimate = (0.5 + 0.5 * S.parts.mantissa) *
+    exp2(S.parts.exponent - 1023);
+
+  double a_n, b_n;
+
+  for(int i = 0; i < 15; i++) {
+    a_n = (x - (estimate * estimate)) / (2 * estimate);
+    b_n = estimate + a_n;
+    estimate = b_n - ((a_n * a_n) / (2 * b_n));
+  }
+
+  return estimate;
+}