case-insensitive equal example added (#1025)

Merging!
Thanks

* case-insensitive example added (#1023)

* resolving issues

* moving the file to the right place

* making iequals to match other examples (#1025)

* comment suggestion update (#1025)

* added case_insensitive_equals.cpp to CMakeLists.txt file (#1025)

examples/CMakeLists.txt

@@ -7,6 +7,7 @@ make_unit( "examples" start_here.cpp )
 
 make_unit( "examples" algorithms/using_existing/memcmp__two_range_algorithms_interface_specifics.cpp )
 make_unit( "examples" algorithms/using_existing/inclusive_scan_zip__using_zip_with_algorithms.cpp )
+make_unit( "examples" algorithms/using_existing/case_insensitive_equals.cpp )
 
 find_package(Threads REQUIRED)
 make_unit( "examples" algorithms/using_existing/inclusive_scan_par_unseq__using_eve_to_build_both_vectorized_and_parallel_algos.cpp )

examples/algorithms/using_existing/case_insensitive_equals.cpp

@@ -0,0 +1,64 @@
+//==================================================================================================
+/*
+  EVE - Expressive Vector Engine
+  Copyright : EVE Contributors & Maintainers
+  SPDX-License-Identifier: MIT
+*/
+//==================================================================================================
+
+
+#include <eve/algo/equal.hpp>
+#include <eve/function/sub.hpp>
+
+#include <cstdint>
+#include <string_view>
+
+namespace ascii
+{
+  struct
+  {
+    // This accepts both std::uint8_t and eve::wide<std::uint8_t>
+    EVE_FORCEINLINE auto operator()(eve::like<std::uint8_t> auto c) const
+    {
+      // if C - 'a' is less than 26, then C is uppercased, otherwide it's lowercased
+      // 'a' < c < 'z' is equivalent to (c - 'a') < 26 because of the underflow
+      return eve::sub[c - 'a' <= 26](c, ('a' - 'A'));
+    }
+
+  } inline constexpr our_to_upper;
+
+  bool iequals(std::string_view a, std::string_view b)
+  {
+    // If they're not the same size, why bother converting them both to uppercase and then check?
+    // btw, it will just crash if the sizes are not equal. You cannot run algo::equal on different sizes.
+    if( a.size() != b.size() )
+      return false;
+
+    // converting them to uint8_t; because our to upper algorithm relies on unsigned integers.
+    auto *f1 = reinterpret_cast<std::uint8_t const *>(a.begin());
+    auto *l1 = reinterpret_cast<std::uint8_t const *>(a.end());
+    auto *f2 = reinterpret_cast<std::uint8_t const *>(b.begin());
+
+    return eve::algo::equal(eve::algo::as_range(f1, l1),
+                            f2,
+                            [](eve::wide<std::uint8_t> a, eve::wide<std::uint8_t> b)
+                            {
+                              // convert both to uppercase and then check if they're equal
+                              return our_to_upper(a) == our_to_upper(b);
+                            });
+  }
+
+}
+
+
+// -----------------------
+
+#include "test.hpp"
+
+TTS_CASE("IEquals, basics")
+{
+  TTS_EQUAL(ascii::iequals("123 One Two aZ", "123 oNe TWo Az"), true);
+  TTS_EQUAL(ascii::iequals("103 One Two aZ", "123 oNe TWo Az"), false);
+  TTS_EQUAL(ascii::iequals("not the same size as", "123 oNe TWo Az"), false);
+  TTS_EQUAL(ascii::iequals("Short", "SHorT"), true);
+};