From 5b1c000a2ecb980393b45d10143d4f918b43f9e9 Mon Sep 17 00:00:00 2001
From: Fabian Homborg <FHomborg@gmail.com>
Date: Tue, 25 Aug 2020 16:45:31 +0200
Subject: [PATCH] math: Add bitwise and/or functions

Just as `math "bitand(5,3)"` and `math "bitor(6,2)"`.

These cast to long long before doing their thing,
so they truncate to an integer, producing weird results with floats.

That's to be expected because float representation is *very*
different, and performing bitwise operations on floats feels quite useless.

Fixes #7281.
---
 doc_src/cmds/math.rst  |  5 +++++
 src/tinyexpr.cpp       | 16 ++++++++++++++++
 tests/checks/math.fish | 14 ++++++++++++++
 3 files changed, 35 insertions(+)

diff --git a/doc_src/cmds/math.rst b/doc_src/cmds/math.rst
index e99fba8b8..ca644c825 100644
--- a/doc_src/cmds/math.rst
+++ b/doc_src/cmds/math.rst
@@ -75,6 +75,7 @@ Functions
 - ``asin``
 - ``atan``
 - ``atan2``
+- ``bitand``, ``bitor`` and ``bitxor`` to perform bitwise operations. These will throw away any non-integer parts and interpret the rest as an int.
 - ``ceil``
 - ``cos``
 - ``cosh``
@@ -114,6 +115,10 @@ Examples
 
 ``math 0xFF`` outputs 255, ``math 0 x 3`` outputs 0 (because it computes 0 multiplied by 3).
 
+``math "bitand(0xFE, 0x2e)"`` outputs 46.
+
+``math "bitor(9,2)"`` outputs 11.
+
 Compatibility notes
 -------------------
 
diff --git a/src/tinyexpr.cpp b/src/tinyexpr.cpp
index 09ffcd5ba..a44503b2e 100644
--- a/src/tinyexpr.cpp
+++ b/src/tinyexpr.cpp
@@ -167,6 +167,19 @@ static double ncr(double n, double r) {
 
 static double npr(double n, double r) { return ncr(n, r) * fac(r); }
 
+
+static constexpr double bit_and(double a, double b) {
+    return static_cast<double>(static_cast<long long>(a) & static_cast<long long>(b));
+}
+
+static constexpr double bit_or(double a, double b) {
+    return static_cast<double>(static_cast<long long>(a) | static_cast<long long>(b));
+}
+
+static constexpr double bit_xor(double a, double b) {
+    return static_cast<double>(static_cast<long long>(a) ^ static_cast<long long>(b));
+}
+
 static const te_builtin functions[] = {
     /* must be in alphabetical order */
     {"abs", reinterpret_cast<const void *>(static_cast<te_fun1>(fabs)), TE_FUNCTION1},
@@ -174,6 +187,9 @@ static const te_builtin functions[] = {
     {"asin", reinterpret_cast<const void *>(static_cast<te_fun1>(asin)), TE_FUNCTION1},
     {"atan", reinterpret_cast<const void *>(static_cast<te_fun1>(atan)), TE_FUNCTION1},
     {"atan2", reinterpret_cast<const void *>(static_cast<te_fun2>(atan2)), TE_FUNCTION2},
+    {"bitand", reinterpret_cast<const void *>(static_cast<te_fun2>(bit_and)), TE_FUNCTION2},
+    {"bitor", reinterpret_cast<const void *>(static_cast<te_fun2>(bit_or)), TE_FUNCTION2},
+    {"bitxor", reinterpret_cast<const void *>(static_cast<te_fun2>(bit_xor)), TE_FUNCTION2},
     {"ceil", reinterpret_cast<const void *>(static_cast<te_fun1>(ceil)), TE_FUNCTION1},
     {"cos", reinterpret_cast<const void *>(static_cast<te_fun1>(cos)), TE_FUNCTION1},
     {"cosh", reinterpret_cast<const void *>(static_cast<te_fun1>(cosh)), TE_FUNCTION1},
diff --git a/tests/checks/math.fish b/tests/checks/math.fish
index b3cab0c4a..4e7636186 100644
--- a/tests/checks/math.fish
+++ b/tests/checks/math.fish
@@ -140,3 +140,17 @@ math "42 >= 1337"
 # CHECKERR: math: Error: Logical operations are not supported, use `test` instead
 # CHECKERR: '42 >= 1337'
 # CHECKERR:     ^
+
+math "bitand(0xFE, 1)"
+# CHECK: 0
+math "bitor(0xFE, 1)"
+# CHECK: 255
+math "bitxor(5, 1)"
+# CHECK: 4
+math "bitand(5.5, 2)"
+# CHECK: 0
+math "bitand(5.5, 1)"
+# CHECK: 1
+
+math "bitor(37 ^ 5, 255)"
+# CHECK: 69343999