Add first implementation of positionless

.clang-format

@@ -1,54 +1,13 @@
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-MacroBlockBegin: ''
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+---
+Language: Cpp
+# Force pointers to the type for C++.
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.clangd

@@ -0,0 +1,5 @@
+CompileFlags:
+  Add:
+    - "-std=c++23"
+    - "-stdlib=libc++"
+  CompilationDatabase: .build

.vscode/settings.json

@@ -1,10 +1,12 @@
 {
     "clangd.arguments": [
-        "--compile-commands-dir=${workspaceFolder}/build",
+        "--compile-commands-dir=${workspaceFolder}/.build",
         "--background-index",
         "--clang-tidy",
         "--completion-style=detailed",
-        "--header-insertion=iwyu",
-        "--query-driver=/usr/bin/clang++"
-    ]
+        "--header-insertion=iwyu"
+    ],
+    "files.associations": {
+        "algorithm": "cpp"
+    }
 }

CMakeLists.txt

@@ -23,6 +23,21 @@ CPMAddPackage(
     VERSION 2.4.12
 )
 
+# Add RapidCheck for property-based testing
+CPMAddPackage(
+    NAME rapidcheck
+    GITHUB_REPOSITORY emil-e/rapidcheck
+    GIT_TAG master
+    OPTIONS "RC_ENABLE_TESTS OFF" "RC_ENABLE_EXAMPLES OFF"
+)
+
+# Suppress deprecation warnings originating from RapidCheck headers only
+if (TARGET rapidcheck)
+    target_compile_options(rapidcheck INTERFACE
+        $<$<CXX_COMPILER_ID:Clang,AppleClang,GNU>:-Wno-deprecated-declarations>
+    )
+endif()
+
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 add_library(positionless INTERFACE)
@@ -32,12 +47,12 @@ target_compile_options(positionless INTERFACE
     $<$<CXX_COMPILER_ID:MSVC>:/W4>
 )
 
-add_executable(unit_tests test/partitioning_tests.cpp)
-target_link_libraries(unit_tests PRIVATE positionless doctest::doctest)
-target_compile_options(unit_tests PRIVATE
-    $<$<CXX_COMPILER_ID:Clang,AppleClang,GNU>:-Wall -Wextra -Wpedantic>
-    $<$<CXX_COMPILER_ID:MSVC>:/W4>
+add_executable(unit_tests
+    test/tests_main.cpp
+    test/partitioning_tests.cpp
+    test/algorithms_tests.cpp
 )
+target_link_libraries(unit_tests PRIVATE positionless doctest::doctest rapidcheck)
 
 enable_testing()
 add_test(NAME unit_tests COMMAND unit_tests)

README.md

@@ -4,7 +4,25 @@ We want to have an implementation of positionless algorithms and a translation f
 
 
 ## Positionless features
-TODO
+- Construction from a range (forward access, bidirectional and random access)
+- `paritioning` accessors:
+  - `parts_count() -> size_t`
+  - `part(size_t part_index) -> std::pair<Iterator, Iterator>`
+  - `is_part_empty(size_t part_index) -> bool`
+  - `part_size(size_t part_index) -> size_t` -- constant time for random access, otherwise linear
+- growing parts (at the end):
+  - `grow`
+  - `grow_by`
+- shrinking parts (for bidirectional collections):
+  - `shrink`
+  - `shrink_by`
+- transferring elements between parts:
+  - `transfer_to_prev`
+  - `transfer_to_next`
+- creation and destruction of parts:
+  - `add_part_end` / `add_part_begin`
+  - `add_parts_end` / `add_parts_begin`
+  - `remove_part`
 
 ## Translation from iterators
 TODO

include/positionless/algorithms.hpp

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "positionless/detail/precondition.hpp"
+#include "positionless/partitioning.hpp"
+
+#include <algorithm>
+#include <iterator>
+
+namespace positionless {
+
+/// Swaps the first element from part `i` with the first element from part `j`.
+///
+/// - Precondition: `i < parts_count()`
+/// - Precondition: `j < parts_count()`
+/// - Precondition: parts `i` and `j` are not empty
+template <std::forward_iterator Iterator>
+inline void swap_first(partitioning<Iterator>& p, size_t i, size_t j) {
+  PRECONDITION(i < p.parts_count());
+  PRECONDITION(j < p.parts_count());
+  PRECONDITION(!p.is_part_empty(i));
+  PRECONDITION(!p.is_part_empty(j));
+
+  auto [begin_i, end_i] = p.part(i);
+  auto [begin_j, end_j] = p.part(j);
+
+  std::iter_swap(begin_i, begin_j);
+}
+
+} // namespace positionless

include/positionless/detail/precondition.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+#if defined(NDEBUG)
+
+/// Assert-like precondition check that calls `std::terminate` on failure.
+#define PRECONDITION(expr)                                                                         \
+  do {                                                                                             \
+    if (!(expr))                                                                                   \
+      std::terminate();                                                                            \
+  } while (false)
+#else
+
+#include <cassert>
+#define PRECONDITION(expr) assert(expr)
+
+#endif