Add url shortcuts (#53)

* add github and gitlab shortcut, closes #52

* update version

* update examples and readme

.travis.yml

@@ -1,11 +1,14 @@
 
 language: cpp
 sudo: require
+dist: xenial
 
 common_sources: &all_sources
   - ubuntu-toolchain-r-test
   - llvm-toolchain-trusty
-  - llvm-toolchain-trusty-6.0
+
+python:
+  - 3.7
 
 matrix:
   include:
@@ -41,10 +44,5 @@ before_install:
   - cmake --version
 
 script:
-  - cmake -Htests/simple -Bbuild/simple 
-  - cmake --build build/simple
-  - CTEST_OUTPUT_ON_FAILURE=1 cmake --build build/simple --target test
-  - cmake -Htests/complex -Bbuild/complex
-  - cmake --build build/complex
-  - CTEST_OUTPUT_ON_FAILURE=1 cmake --build build/complex --target test
+  - python3 examples/run_all.py
  

README.md

@@ -2,50 +2,177 @@
 
 # CPM
 
-CPM is a minimalistic package manager written in Cmake using `find_package` and `FetchContent` as a fallback to download non locally installed packages.
+CPM is a CMake script that adds dependency management capabilities to CMake. 
+It's built as an extension of CMake's [FetchContent](https://cmake.org/cmake/help/latest/module/FetchContent.html) module that adds version control and simpler usage.
 
-# Usage
+## Supported projects
 
-To add a new dependency to your project simply add the Projects target name, the git URL and the version. If the git tag for this version does not match the pattern `v$VERSION`, then the exact branch or tag can be specified with the `GIT_TAG` argument. CMake options can also be supplied with the package.
+Any project that you can add via `add_subdirectory` should already work with CPM.
+
+## Usage
+
+After `CPM.cmake` has been added to your project, the function `CPMAddPackage` can be used to fetch and configure all dependencies.
+Afterwards all targets defined in the dependencies can be used.
+`CPMAddPackage` takes the following named arguments.
+
+```cmake
+CPMAddPackage(
+  NAME          # The name of the dependency (should be chosen to match the main target's name)
+  VERSION       # The minimum version of the dependency (optional, defaults to 0)
+  OPTIONS       # Configuration options passed to the dependency (optional)
+  DOWNLOAD_ONLY # If set, the project is downloaded, but not configured (optional)
+  [...]         # Origin paramters forwarded to FetchContent_Declare, see below
+)
+```
+
+The origin is usually specified by a `GIT_REPOSITORY`, but [svn revisions and direct URLs are also supported](https://cmake.org/cmake/help/latest/module/FetchContent.html#declaring-content-details).
+If `GIT_TAG` hasn't been explicitly specified it defaults to `v(VERSION)`, a common convention for github projects.
+`GIT_TAG` can also be set to a branch name such as `master` to download the most recent version.
+
+Besides downloading and to configuring the dependency, the following variables are defined in the local scope, where `(DEPENDENCY)` is the name of the dependency.
+
+- `(DEPENDENCY)_SOURCE_DIR` is the path to the source of the dependency.
+- `(DEPENDENCY)_BINARY_DIR` is the path to the build directory of the dependency.
+- `(DEPENDENCY)_ADDED` is set to `YES` if the dependency has not been added before, otherwise it is set to `NO`.
+
+## Full Example
 
 ```cmake
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
+# create project
 project(MyProject)
 
 # add dependencies
-include(${CMAKE_CURRENT_SOURCE_DIR}/cmake/CPM.cmake)
+include(cmake/CPM.cmake)
 
 CPMAddPackage(
   NAME LarsParser
-  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
   VERSION 1.8
-  OPTIONS 
+  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
+  OPTIONS
     "LARS_PARSER_BUILD_GLUE_EXTENSION ON"
 )
 
 # add executable
-set (CMAKE_CXX_STANDARD 17)
-add_executable(my-project my-project.cpp)
-target_link_libraries(my-project LarsParser)
+add_executable(myProject myProject.cpp)
+set_target_properties(myProject PROPERTIES CXX_STANDARD 17)
+target_link_libraries(myProject LarsParser)
 ```
 
-# Adding CPM
+See the [examples directory](https://github.com/TheLartians/CPM/tree/master/examples) for more examples with source code.
 
-To add CPM to your current project, simply include add `cmake/CPM.cmake` to your projects `cmake` directory. The command below will perform this automatically.
+## Adding CPM
+
+To add CPM to your current project, simply add `cmake/CPM.cmake` to your project's `cmake` directory. The command below will perform this automatically.
 
 ```bash
 wget -O cmake/CPM.cmake https://raw.githubusercontent.com/TheLartians/CPM/master/cmake/CPM.cmake
 ```
 
-# Advantages
+## Updating CPM
 
-- **Auto handle dependencies** Users of your projects do not need to worry about dependencies, everything is handled automatically.
-- **Reproducable builds** Using git tags it is ensured that a project will always be in the same state everywhere.
-- **No installation required** No need to install any third-party package managers. Just copy the files from the CMake directory and you're good to go.
-- **Cross-Plattform** As CPM adds projects as cmake subdirectories, it is compatible with all cmake toolchains and generators. 
+To update CPM to the newest version, simply update the script in the project's cmake directory, for example by running the command above. Dependencies using CPM will automatically use the updated script of the outermost project.
 
-# Limitations
+## Snipplets
 
-- **First version used** In diamond-shaped dependency graphs (e.g. `A` depends on `C`(v1.1) and `A` depends on `B` depends on `C`(v1.2)) the first added dependency will be used (in this case `C`@1.1).
-- **No auto-update** To update a dependency, version numbers or git tags in the cmake scripts must be adapted manually.
+These examples demonstrate how to include some well-known projects with CPM.
+
+### [Catch2](https://github.com/catchorg/Catch2.git)
+
+Has a CMakeLists.txt that supports `add_subdirectory`.
+
+```cmake
+CPMAddPackage(
+  NAME Catch2
+  GITHUB_REPOSITORY catchorg/Catch2
+  VERSION 2.5.0
+)
+```
+
+See [here](https://github.com/TheLartians/CPM/blob/master/examples/doctest/CMakeLists.txt) for doctest example.
+Note that we can shorten Github and Gitlab URLs by using `GITHUB_REPOSITORY` or `GITLAB_REPOSITORY`, respectively.
+
+### [google/benchmark](https://github.com/google/benchmark.git)
+
+Has a CMakeLists.txt that supports `add_subdirectory`, but needs some configuring to work without external dependencies.
+
+```cmake
+CPMAddPackage(
+  NAME benchmark
+  GITHUB_REPOSITORY google/benchmark
+  VERSION 1.4.1
+  OPTIONS
+    "BENCHMARK_ENABLE_TESTING Off"
+)
+
+# needed to compile with C++17
+set_target_properties(benchmark PROPERTIES CXX_STANDARD 17)
+```
+
+### [nlohmann/json](https://github.com/nlohmann/json)
+
+Header-only library with a huge git repositoy.
+Instead of downloading the whole repositoy, we fetch the zip included with the release and create our own target.
+
+```cmake
+CPMAddPackage(
+  NAME nlohmann_json
+  VERSION 3.6.1  
+  URL https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip
+  URL_HASH SHA256=69cc88207ce91347ea530b227ff0776db82dcb8de6704e1a3d74f4841bc651cf
+)
+
+if (nlohmann_json_ADDED)
+  add_library(nlohmann_json INTERFACE)
+  target_include_directories(nlohmann_json INTERFACE ${nlohmann_json_SOURCE_DIR})
+endif()
+```
+
+Adding large repos works as well, but takes a while for the initial clone.
+
+### [Lua](https://www.lua.org)
+
+Lua does not oficially support CMake, so we query the sources and create our own target.
+
+```cmake
+CPMAddPackage(
+  NAME lua
+  GIT_REPOSITORY https://github.com/lua/lua.git
+  VERSION 5-3-4
+  DOWNLOAD_ONLY YES
+)
+
+if (lua_ADDED)
+  FILE(GLOB lua_sources ${lua_SOURCE_DIR}/*.c)
+  add_library(lua STATIC ${lua_sources})
+
+  target_include_directories(lua
+    PUBLIC
+      $<BUILD_INTERFACE:${lua_SOURCE_DIR}>
+  )
+endif()
+```
+
+## Local packages
+
+CPM can be configured to use `find_package` to search for locally installed dependencies first.
+If `CPM_LOCAL_PACKAGES_ONLY` is set, CPM will error when dependency is not found locally.
+
+## Advantages
+
+- **Small and reusable projects** CPM takes care of project dependencies, allowing developers to focus on creating small, well-tested frameworks.
+- **Cross-Plattform** CPM adds projects via `add_subdirectory`, which is compatible with all cmake toolchains and generators.
+- **Reproducable builds** By using versioning via git tags it is ensured that a project will always be in the same state everywhere.
+- **Recursive dependencies** Ensures that no dependency is added twice and is added in the minimum required version.
+- **No installation required** No need to install anything. Just add the script to your project and you're good to go.
+- **No Setup required** There is a good chance your existing projects already work as CPM dependencies.
+- **Simple source distribution** CPM makes including projects with source files and dependencies easy, reducing the need for monolithic header files.
+
+## Limitations
+
+- **First version used** In diamond-shaped dependency graphs (e.g. `A` depends on `C`@1.1 and `B`, which itself depends on `C`@1.2 the first added dependency will be used (in this case `C`@1.1). In this case, B requires a newer version of `C` than `A`, so CPM will emit an error. This can be resolved by updating the outermost dependency version.
+- **No auto-update** To update a dependency, version must be adapted manually and there is no way for CPM to figure out the most recent version.
+- **No pre-built binaries** Unless they are installed or included in the linked repository. 
+
+For projects with more complex needs and where an extra setup step doesn't matter, it is worth to check out fully featured C++ package managers such as [conan](https://conan.io) or [hunter](https://github.com/ruslo/hunter).

cmake/CPM.cmake

@@ -1,38 +1,69 @@
+# TheLartians/CPM - A simple Git dependency manager
+# =================================================
+# See https://github.com/TheLartians/CPM for usage and update instructions.
+#
+# MIT License
+# ----------- 
+#[[
+  Copyright (c) 2019 Lars Melchior
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in all
+  copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+]]
+
 cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
 
+set(CURRENT_CPM_VERSION 0.11) 
+
 if(CPM_DIRECTORY)
   if(NOT ${CPM_DIRECTORY} MATCHES ${CMAKE_CURRENT_LIST_DIR})
+    if (${CPM_VERSION} VERSION_LESS ${CURRENT_CPM_VERSION})
+      CPM_HANDLE_OLD_VERSION(${CURRENT_CPM_VERSION})  
+    endif()
     return()
   endif()
 endif()
 
-option(CPM_LOCAL_PACKAGES_ONLY "Use only locally installed packages" OFF)
-option(CPM_REMOTE_PACKAGES_ONLY "Always download packages" OFF)
-
+set(CPM_VERSION ${CURRENT_CPM_VERSION} CACHE INTERNAL "")
 set(CPM_DIRECTORY ${CMAKE_CURRENT_LIST_DIR} CACHE INTERNAL "")
 set(CPM_PACKAGES "" CACHE INTERNAL "")
 
+option(CPM_USE_LOCAL_PACKAGES "Use locally installed packages (find_package)" OFF)
+option(CPM_LOCAL_PACKAGES_ONLY "Use only locally installed packages" OFF)
+
 include(FetchContent)
 include(CMakeParseArguments)
 
-function(CPMRegisterPackage PACKAGE VERSION)
-  LIST(APPEND CPM_PACKAGES ${CPM_ARGS_NAME})
-  set(CPM_PACKAGES ${CPM_PACKAGES} CACHE INTERNAL "")
-  set(PACKAGE_VERSION_VARIABLE "CPM_PACKAGE_${PACKAGE}_VERSION")
-  set(${PACKAGE_VERSION_VARIABLE} ${VERSION} CACHE INTERNAL "")
-endfunction()
-
-function(CPMGetPreviousPackageVersion PACKAGE)
-  set(PACKAGE_VERSION_VARIABLE "CPM_PACKAGE_${PACKAGE}_VERSION")
-  set(CPM_PREVIOUS_PACKAGE_VERSION "${${PACKAGE_VERSION_VARIABLE}}" PARENT_SCOPE)
-endfunction()
+# Initialize logging prefix
+if(NOT CPM_INDENT)
+  set(CPM_INDENT "CPM:")
+endif()
 
+# The main workhorse of CPM
 function(CPMAddPackage)
-    
+
   set(oneValueArgs
     NAME
     VERSION
     GIT_TAG
+    DOWNLOAD_ONLY
+    GITHUB_REPOSITORY
+    GITLAB_REPOSITORY
   )
 
   set(multiValueArgs
@@ -41,57 +72,139 @@ function(CPMAddPackage)
 
   cmake_parse_arguments(CPM_ARGS "" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
 
-  if (NOT CPM_ARGS_GIT_TAG)
-    set(CPM_ARGS_GIT_TAG v${CPM_ARGS_VERSION})
-  endif()
-
-  if (${CPM_ARGS_NAME} IN_LIST CPM_PACKAGES)
-    CPMGetPreviousPackageVersion(${CPM_ARGS_NAME})
-    message(STATUS "CPM: SKIP ${CPM_ARGS_NAME}@${CPM_ARGS_GIT_TAG}: already addded package ${CPM_ARGS_NAME}@${CPM_PREVIOUS_PACKAGE_VERSION}")
-    return()
-  endif()
-
-  CPMRegisterPackage(${CPM_ARGS_NAME} ${CPM_ARGS_GIT_TAG})
-
-  if (CPM_ARGS_OPTIONS)
-    foreach(OPTION ${CPM_ARGS_OPTIONS})
-      string(REGEX MATCH "^[^ ]+" OPTION_KEY ${OPTION})
-      string(LENGTH ${OPTION_KEY} OPTION_KEY_LENGTH)
-      math(EXPR OPTION_KEY_LENGTH "${OPTION_KEY_LENGTH}+1")
-      string(SUBSTRING ${OPTION} "${OPTION_KEY_LENGTH}" "-1" OPTION_VALUE)
-      set(${OPTION_KEY} ${OPTION_VALUE} CACHE INTERNAL "")
-    endforeach()
-  endif()
-
-  if (NOT ${CPM_REMOTE_PACKAGES_ONLY})
+  if(${CPM_USE_LOCAL_PACKAGES} OR ${CPM_LOCAL_PACKAGES_ONLY}) 
     find_package(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION} QUIET)
-    set(CPM_PACKAGE_FOUND ${CPM_ARGS_NAME}_FOUND)
 
     if(${CPM_PACKAGE_FOUND})
-      message(STATUS "CPM: ADD local package ${CPM_ARGS_NAME}@${CPM_ARGS_VERSION}")
+      message(STATUS "CPM: adding local package ${CPM_ARGS_NAME}@${CPM_ARGS_VERSION}")
       set_target_properties(${CPM_ARGS_NAME} 
         PROPERTIES
           IMPORTED_GLOBAL True
       )
       return()
     endif()
+
+    if(${CPM_LOCAL_PACKAGES_ONLY}) 
+      message(SEND_ERROR "CPM: ${CPM_ARGS_NAME} not found via find_package(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION})")
+    endif()
   endif()
 
-  if (NOT ${CPM_LOCAL_PACKAGES_ONLY})
+  if (NOT CPM_ARGS_VERSION)
+    set(CPM_ARGS_VERSION 0)
+  endif()
 
-    message(STATUS "CPM: ADD remote package ${CPM_ARGS_NAME}@${CPM_ARGS_GIT_TAG}")
+  if (NOT CPM_ARGS_GIT_TAG)
+    set(CPM_ARGS_GIT_TAG v${CPM_ARGS_VERSION})
+  endif()
 
-    set(CPM_PACKAGE_CONTENT ${CPM_ARGS_NAME}_CONTENT)
+  list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_TAG ${CPM_ARGS_GIT_TAG})
 
-    FetchContent_Declare(
-      ${CPM_PACKAGE_CONTENT}
-      GIT_TAG ${CPM_ARGS_GIT_TAG}
-      ${CPM_ARGS_UNPARSED_ARGUMENTS}
-    )
-    
-    FetchContent_MakeAvailable(${CPM_PACKAGE_CONTENT})
+  if(CPM_ARGS_DOWNLOAD_ONLY)
+    set(DOWNLOAD_ONLY ${CPM_ARGS_DOWNLOAD_ONLY})
   else()
-    MESSAGE(ERROR "CPM could not find the local package ${CPM_ARGS_NAME}@${CPM_ARGS_VERSION}")
+    set(DOWNLOAD_ONLY NO)
   endif()
 
+  if (CPM_ARGS_GITHUB_REPOSITORY)
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_REPOSITORY "https://github.com/${CPM_ARGS_GITHUB_REPOSITORY}.git")
+  endif()
+
+  if (CPM_ARGS_GITLAB_REPOSITORY)
+    list(APPEND CPM_ARGS_UNPARSED_ARGUMENTS GIT_REPOSITORY "https://gitlab.com/${CPM_ARGS_GITHUB_REPOSITORY}.git")
+  endif()
+
+  if (${CPM_ARGS_NAME} IN_LIST CPM_PACKAGES)
+    CPM_GET_PACKAGE_VERSION(${CPM_ARGS_NAME})
+    if(${CPM_PACKAGE_VERSION} VERSION_LESS ${CPM_ARGS_VERSION})
+      message(WARNING "${CPM_INDENT} requires a newer version of ${CPM_ARGS_NAME} (${CPM_ARGS_VERSION}) than currently included (${CPM_PACKAGE_VERSION}).")
+    endif()
+    if (CPM_ARGS_OPTIONS)
+      foreach(OPTION ${CPM_ARGS_OPTIONS})
+        CPM_PARSE_OPTION(${OPTION})
+        if(NOT "${${OPTION_KEY}}" STREQUAL ${OPTION_VALUE})
+          message(WARNING "${CPM_INDENT} ignoring package option for ${CPM_ARGS_NAME}: ${OPTION_KEY} = ${OPTION_VALUE} (${${OPTION_KEY}})")
+        endif()
+      endforeach()
+    endif()
+    CPM_FETCH_PACKAGE(${CPM_ARGS_NAME} ${DOWNLOAD_ONLY})
+    CPMGetProperties(${CPM_ARGS_NAME})
+    SET(${CPM_ARGS_NAME}_SOURCE_DIR "${${CPM_ARGS_NAME}_SOURCE_DIR}" PARENT_SCOPE)
+    SET(${CPM_ARGS_NAME}_BINARY_DIR "${${CPM_ARGS_NAME}_BINARY_DIR}" PARENT_SCOPE)  
+    SET(${CPM_ARGS_NAME}_ADDED NO PARENT_SCOPE)  
+    return()
+  endif()
+
+  CPMRegisterPackage(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION})
+
+  if (CPM_ARGS_OPTIONS)
+    foreach(OPTION ${CPM_ARGS_OPTIONS})
+      CPM_PARSE_OPTION(${OPTION})
+      set(${OPTION_KEY} ${OPTION_VALUE} CACHE INTERNAL "")
+    endforeach()
+  endif()
+
+  CPM_DECLARE_PACKAGE(${CPM_ARGS_NAME} ${CPM_ARGS_VERSION} ${CPM_ARGS_GIT_TAG} "${CPM_ARGS_UNPARSED_ARGUMENTS}")
+  CPM_FETCH_PACKAGE(${CPM_ARGS_NAME} ${DOWNLOAD_ONLY})
+  CPMGetProperties(${CPM_ARGS_NAME})
+  SET(${CPM_ARGS_NAME}_SOURCE_DIR "${${CPM_ARGS_NAME}_SOURCE_DIR}" PARENT_SCOPE)
+  SET(${CPM_ARGS_NAME}_BINARY_DIR "${${CPM_ARGS_NAME}_BINARY_DIR}" PARENT_SCOPE)
+  SET(${CPM_ARGS_NAME}_ADDED YES PARENT_SCOPE)  
 endfunction()
+
+function (CPM_DECLARE_PACKAGE PACKAGE VERSION GIT_TAG)
+  message(STATUS "${CPM_INDENT} adding package ${PACKAGE}@${VERSION} (${GIT_TAG})")
+
+  FetchContent_Declare(
+    ${PACKAGE}
+    ${ARGN}
+  )
+endfunction()
+
+function (CPM_FETCH_PACKAGE PACKAGE DOWNLOAD_ONLY)  
+  set(CPM_OLD_INDENT "${CPM_INDENT}")
+  set(CPM_INDENT "${CPM_INDENT} ${PACKAGE}:")
+  if(${DOWNLOAD_ONLY})
+    if(NOT "${PACKAGE}_POPULATED")
+      FetchContent_Populate(${PACKAGE})
+    endif()
+  else()
+    FetchContent_MakeAvailable(${PACKAGE})
+  endif()
+  set(CPM_INDENT "${CPM_OLD_INDENT}")
+endfunction()
+
+function (CPMGetProperties PACKAGE)
+  FetchContent_GetProperties(${PACKAGE})
+  string(TOLOWER ${PACKAGE} lpackage)
+  SET(${PACKAGE}_SOURCE_DIR "${${lpackage}_SOURCE_DIR}" PARENT_SCOPE)
+  SET(${PACKAGE}_BINARY_DIR "${${lpackage}_BINARY_DIR}" PARENT_SCOPE)
+endfunction()
+
+function(CPMRegisterPackage PACKAGE VERSION)
+  list(APPEND CPM_PACKAGES ${PACKAGE})
+  set(CPM_PACKAGES ${CPM_PACKAGES} CACHE INTERNAL "")
+  set("CPM_PACKAGE_${PACKAGE}_VERSION" ${VERSION} CACHE INTERNAL "")
+endfunction()
+
+function(CPM_GET_PACKAGE_VERSION PACKAGE)
+  set(CPM_PACKAGE_VERSION "${CPM_PACKAGE_${PACKAGE}_VERSION}" PARENT_SCOPE)
+endfunction()
+
+function(CPM_PARSE_OPTION OPTION)
+  string(REGEX MATCH "^[^ ]+" OPTION_KEY ${OPTION})
+  string(LENGTH ${OPTION_KEY} OPTION_KEY_LENGTH)
+  math(EXPR OPTION_KEY_LENGTH "${OPTION_KEY_LENGTH}+1")
+  string(SUBSTRING ${OPTION} "${OPTION_KEY_LENGTH}" "-1" OPTION_VALUE)
+  set(OPTION_KEY "${OPTION_KEY}" PARENT_SCOPE)
+  set(OPTION_VALUE "${OPTION_VALUE}" PARENT_SCOPE)
+endfunction()
+
+function (CPM_HANDLE_OLD_VERSION NEW_CPM_VERSION)
+  
+  message(AUTHOR_WARNING "${CPM_INDENT} \
+A dependency is using a more recent CPM (${NEW_CPM_VERSION}) than the current project (${CPM_VERSION}). \
+It is recommended to upgrade CPM to the most recent version. \
+See https://github.com/TheLartians/CPM for more information."
+  )
+
+endfunction()

examples/benchmark/CMakeLists.txt

@@ -0,0 +1,30 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME fibonacci
+  GIT_REPOSITORY https://github.com/TheLartians/Fibonacci.git
+  VERSION 1.0
+)
+
+CPMAddPackage(
+  NAME benchmark
+  GITHUB_REPOSITORY google/benchmark
+  VERSION 1.4.1
+  OPTIONS
+    "BENCHMARK_ENABLE_TESTING Off"
+)
+
+if (benchmark_ADDED)
+  # patch google benchmark target
+  set_target_properties(benchmark PROPERTIES CXX_STANDARD 17)
+endif()
+
+# ---- Executable ----
+
+add_executable(CPMExampleBenchmark "main.cpp")
+set_target_properties(CPMExampleBenchmark PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMExampleBenchmark fibonacci benchmark)

examples/benchmark/main.cpp

@@ -0,0 +1,36 @@
+#include <benchmark/benchmark.h>
+#include <vector>
+#include <algorithm>
+#include <random>
+
+#include <fibonacci.h>
+
+
+std::vector<unsigned> createTestNumbers(){
+  std::vector<unsigned> v;
+  for (int i=0;i<25;++i) v.emplace_back(i);
+  std::random_device rd;
+  std::mt19937 g(rd());
+  std::shuffle(v.begin(), v.end(), g);
+  return v;
+}
+
+void fibonnacci(benchmark::State& state) {
+  auto numbers = createTestNumbers();
+  for (auto _ : state) {
+    for (auto v: numbers) benchmark::DoNotOptimize(fibonnacci(v));
+  }
+}
+
+BENCHMARK(fibonnacci);
+
+void fastFibonacci(benchmark::State& state) {
+  auto numbers = createTestNumbers();
+  for (auto _ : state) {
+    for (auto v: numbers) benchmark::DoNotOptimize(fastFibonacci(v));
+  }
+}
+
+BENCHMARK(fastFibonacci);
+
+BENCHMARK_MAIN();

examples/catch2/CMakeLists.txt

@@ -0,0 +1,39 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Options ----
+
+option(ENABLE_TEST_COVERAGE "Enable test coverage" OFF)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME fibonacci
+  GIT_REPOSITORY https://github.com/TheLartians/Fibonacci.git
+  VERSION 1.0
+)
+
+CPMAddPackage(
+  NAME Catch2
+  GITHUB_REPOSITORY catchorg/Catch2
+  VERSION 2.5.0
+)
+
+# ---- Create binary ----
+
+add_executable(CPMExampleCatch2 main.cpp)
+target_link_libraries(CPMExampleCatch2 fibonacci Catch2)
+set_target_properties(CPMExampleCatch2 PROPERTIES CXX_STANDARD 17 COMPILE_FLAGS "-Wall -pedantic -Wextra -Werror")
+
+# ---- Enable testing ----
+
+ENABLE_TESTING() 
+ADD_TEST(CPMExampleCatch2 CPMExampleCatch2)
+
+# ---- Add code coverage ----
+
+if (${ENABLE_TEST_COVERAGE})
+  set_target_properties(CPMExampleCatch2 PROPERTIES CXX_STANDARD 17 COMPILE_FLAGS "-O0 -g -fprofile-arcs -ftest-coverage --coverage")
+  target_link_options(CPMExampleCatch2 PUBLIC "--coverage")
+endif()

examples/catch2/main.cpp

@@ -0,0 +1,20 @@
+#define CATCH_CONFIG_MAIN
+
+#include <catch2/catch.hpp>
+#include <fibonacci.h>
+
+TEST_CASE("fibonnacci"){
+  REQUIRE(fibonnacci(0) == 0);
+  REQUIRE(fibonnacci(1) == 1);
+  REQUIRE(fibonnacci(2) == 1);
+  REQUIRE(fibonnacci(3) == 2);
+  REQUIRE(fibonnacci(4) == 3);
+  REQUIRE(fibonnacci(5) == 5);
+  REQUIRE(fibonnacci(13) == 233);
+}
+
+TEST_CASE("fastFibonnacci"){
+  for (unsigned i=0; i<25; ++i){
+    REQUIRE(fibonnacci(i) == fastFibonacci(i));
+  }
+}

examples/doctest/CMakeLists.txt

@@ -0,0 +1,40 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Options ----
+
+option(ENABLE_TEST_COVERAGE "Enable test coverage" OFF)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME fibonacci
+  GIT_REPOSITORY https://github.com/TheLartians/Fibonacci.git
+  VERSION 1.0
+)
+
+CPMAddPackage(
+  NAME doctest
+  GITHUB_REPOSITORY onqtam/doctest
+  VERSION 2.3.2
+  GIT_TAG 2.3.2
+)
+
+# ---- Create binary ----
+
+add_executable(CPMExampleDoctest main.cpp)
+target_link_libraries(CPMExampleDoctest fibonacci doctest)
+set_target_properties(CPMExampleDoctest PROPERTIES CXX_STANDARD 17 COMPILE_FLAGS "-Wall -pedantic -Wextra -Werror")
+
+# ---- Enable testing ----
+
+ENABLE_TESTING() 
+ADD_TEST(CPMExampleDoctest CPMExampleDoctest)
+
+# ---- Add code coverage ----
+
+if (${ENABLE_TEST_COVERAGE})
+  set_target_properties(CPMExampleDoctest PROPERTIES CXX_STANDARD 17 COMPILE_FLAGS "-O0 -g -fprofile-arcs -ftest-coverage --coverage")
+  target_link_options(CPMExampleDoctest PUBLIC "--coverage")
+endif()

examples/doctest/main.cpp

@@ -0,0 +1,20 @@
+#define DOCTEST_CONFIG_IMPLEMENT_WITH_MAIN
+
+#include <doctest/doctest.h>
+#include <fibonacci.h>
+
+TEST_CASE("fibonnacci"){
+  CHECK(fibonnacci(0) == 0);
+  CHECK(fibonnacci(1) == 1);
+  CHECK(fibonnacci(2) == 1);
+  CHECK(fibonnacci(3) == 2);
+  CHECK(fibonnacci(4) == 3);
+  CHECK(fibonnacci(5) == 5);
+  CHECK(fibonnacci(13) == 233);
+}
+
+TEST_CASE("fastFibonnacci"){
+  for (unsigned i=0; i<25; ++i){
+    CHECK(fibonnacci(i) == fastFibonacci(i));
+  }
+}

examples/json/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME nlohmann_json
+  VERSION 3.6.1  
+  # not using the repo as it takes forever to clone
+  URL https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip
+  URL_HASH SHA256=69cc88207ce91347ea530b227ff0776db82dcb8de6704e1a3d74f4841bc651cf
+)
+
+if(nlohmann_json_ADDED)
+  add_library(nlohmann_json INTERFACE)
+  target_include_directories(nlohmann_json INTERFACE ${nlohmann_json_SOURCE_DIR})
+endif()
+
+# ---- Executable ----
+
+add_executable(CPMJSONExample "main.cpp")
+set_target_properties(CPMJSONExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMJSONExample nlohmann_json)

examples/json/main.cpp

@@ -0,0 +1,25 @@
+#include <nlohmann/json.hpp>
+#include <iostream>
+#include <iomanip>
+
+int main(){
+  
+  nlohmann::json json = {
+    {"pi", 3.141},
+    {"happy", true},
+    {"name", "Niels"},
+    {"nothing", nullptr},
+    {"answer", {
+      {"everything", 42}
+    }},
+    {"list", {1, 0, 2}},
+    {"object", {
+      {"currency", "USD"},
+      {"value", 42.99}
+    }}
+  };
+
+  std::cout << "declared JSON object: " << std::setw(2) << json << std::endl;
+
+  return 0;
+}

examples/parser-lua/CMakeLists.txt

@@ -0,0 +1,28 @@
+cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
+
+include(../../cmake/CPM.cmake)
+
+# ---- Dependencies ----
+
+CPMAddPackage(
+  NAME Glue
+  GIT_REPOSITORY https://github.com/TheLartians/Glue.git
+  VERSION 0.8.1
+  OPTIONS 
+    "GLUE_ENABLE_LUA ON"
+    "GLUE_BUILD_LUA ON"
+)
+
+CPMAddPackage(
+  NAME LarsParser
+  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
+  VERSION 1.9
+  OPTIONS 
+    "LARS_PARSER_BUILD_GLUE_EXTENSION ON"
+)
+
+# ---- Create binary ----
+
+add_executable(parser-lua main.cpp)
+set_target_properties(parser-lua PROPERTIES CXX_STANDARD 17)
+target_link_libraries(parser-lua LHC LarsParser Glue)

examples/parser-lua/main.cpp

@@ -0,0 +1,46 @@
+#include <lars/parser/extension.h>
+#include <glue/lua.h>
+#include <stdexcept>
+#include <iostream>
+
+int main() {
+  auto lua = glue::LuaState();
+  lua.openStandardLibs();
+
+  lua["parser"] = lars::glue::parser();
+  
+  lua.run(R"(
+    wordParser = parser.Program.create()
+
+    wordParser:setRule("Whitespace", "[ \t]")
+    wordParser:setSeparatorRule("Whitespace")
+
+    wordParser:setRule("Word", "[a-zA-Z]+")
+    
+    wordParser:setRuleWithCallback("Words", "Word*", function(e) 
+      local N = e:size()
+      local res = {}
+      for i=0,N-1 do res[#res+1] = e:get(i):string() end
+      return res
+    end)
+
+    wordParser:setStartRule("Words")
+  )");
+
+  lua.run(R"(
+    while true do
+      print("please enter some words or 'quit' to exit");
+      local input = io.read();
+      if input == "quit" then os.exit() end
+      local result
+      ok, err = pcall(function() result = wordParser:run(input) end)
+      if ok then
+        print("you entered " .. #result .. " words!")
+      else 
+        print("error: " .. tostring(err))
+      end
+    end
+  )");
+
+  return 0;
+}

examples/parser/CMakeLists.txt

@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
+
+# add dependencies
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME LarsParser
+  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
+  VERSION 1.7
+)
+
+# add executable
+add_executable(calculator main.cpp)
+set_target_properties(calculator PROPERTIES CXX_STANDARD 17)
+target_link_libraries(calculator LarsParser)

examples/parser/main.cpp

@@ -0,0 +1,57 @@
+#include <iostream>
+#include <unordered_map>
+#include <cmath>
+
+#include <lars/parser/generator.h>
+
+int main() {
+  using namespace std;
+  using VariableMap = unordered_map<string, float>;
+  
+  lars::ParserGenerator<float, VariableMap &> calculator;
+  
+  auto &g = calculator;
+  g.setSeparator(g["Whitespace"] << "[\t ]");
+
+  g["Expression"] << "Set | Sum";
+  g["Set"       ] << "Name '=' Sum" >> [](auto e, auto &v){ return v[e[0].string()] = e[1].evaluate(v); };
+  g["Sum"       ] << "Add | Subtract | Product";
+  g["Product"   ] << "Multiply | Divide | Exponent";
+  g["Exponent"  ] << "Power | Atomic";
+  g["Atomic"    ] << "Number | Brackets | Variable";
+  g["Brackets"  ] << "'(' Sum ')'";
+  g["Add"       ] << "Sum '+' Product"       >> [](auto e, auto &v){ return e[0].evaluate(v) + e[1].evaluate(v); };
+  g["Subtract"  ] << "Sum '-' Product"       >> [](auto e, auto &v){ return e[0].evaluate(v) - e[1].evaluate(v); };
+  g["Multiply"  ] << "Product '*' Exponent"  >> [](auto e, auto &v){ return e[0].evaluate(v) * e[1].evaluate(v); };
+  g["Divide"    ] << "Product '/' Exponent"  >> [](auto e, auto &v){ return e[0].evaluate(v) / e[1].evaluate(v); };
+  g["Power"     ] << "Atomic ('^' Exponent)" >> [](auto e, auto &v){ return pow(e[0].evaluate(v), e[1].evaluate(v)); };
+  g["Variable"  ] << "Name" >> [](auto e, auto &v){ return v[e[0].string()]; };
+  g["Name"      ] << "[a-zA-Z] [a-zA-Z0-9]*";
+  g["Number"    ] << "'-'? [0-9]+ ('.' [0-9]+)?" >> [](auto e, auto &){ return stod(e.string()); };
+
+  g.setStart(g["Expression"]);
+
+  cout << "Enter an expression to be evaluated or 'quit' to exit.\n";
+
+  VariableMap variables;
+
+  while (true) {
+    string str;
+    cout << "> ";
+    getline(cin,str);
+    if(str == "q" || str == "quit"){ break; }
+    try {
+      auto result = calculator.run(str, variables);
+      cout << str << " = " << result << endl;
+    } catch (lars::SyntaxError &error) {
+      auto syntax = error.syntax;
+      cout << "  ";
+      cout << string(syntax->begin, ' ');
+      cout << string(syntax->length(), '~');
+      cout << "^\n";
+      cout << "  " << "Syntax error while parsing " << syntax->rule->name << endl;
+    }
+  }
+
+  return 0;
+}

examples/run_all.py

@@ -0,0 +1,29 @@
+#!/usr/bin/python3
+
+from pathlib import Path
+from subprocess import PIPE, run
+
+examples = [
+  x for x in Path(__file__).parent.iterdir() if x.is_dir() and (x / 'CMakeLists.txt').exists()
+]
+
+assert(len(examples) > 0)
+
+def runCommand(command):
+  print('- %s' % command)
+  result = run(command, stdout=PIPE, stderr=PIPE, universal_newlines=True, shell=True)
+  if result.returncode != 0:
+    print("error while running '%s':\n" % command, '  ' + str(result.stderr).replace('\n','\n  '))
+    exit(result.returncode)
+  return result.stdout
+
+print('')
+for example in examples:
+  print("running example %s" % example.name)
+  print("================" + ('=' * len(example.name)))
+  project = Path(".") / 'build' / example.name
+  configure = runCommand('cmake -H%s -B%s -DCMAKE_BUILD_TYPE=RelWithDebInfo' % (example, project))
+  print('  ' + '\n  '.join([line for line in configure.split('\n') if 'CPM:' in line]))
+  build = runCommand('cmake --build %s -j4' % (project))
+  print('  ' + '\n  '.join([line for line in build.split('\n') if 'Built target' in line]))
+  print('')

examples/simple_match/CMakeLists.txt

@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME simple_match
+  GIT_REPOSITORY https://github.com/jbandela/simple_match.git
+  GIT_TAG a3ab17f3d98db302de68ad85ed399a42ae41889e
+  DOWNLOAD_ONLY True
+)
+
+if(simple_match_ADDED)
+  add_library(simple_match INTERFACE IMPORTED)
+  target_include_directories(simple_match INTERFACE "${simple_match_SOURCE_DIR}/include")
+endif()
+
+# ---- Executable ----
+
+add_executable(CPMSimpleMatchExample "main.cpp")
+set_target_properties(CPMSimpleMatchExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMSimpleMatchExample simple_match)
+

examples/simple_match/main.cpp

@@ -0,0 +1,34 @@
+#include <simple_match/simple_match.hpp>
+
+#include <iostream>
+
+int main(int argc, char ** argv){
+  using namespace simple_match;
+  using namespace simple_match::placeholders;
+
+  std::string input;
+  std::cout << "please enter a number or 'quit' to exit" << std::endl;
+
+  while (true) {
+    std::cout << "> ";
+    std::getline(std::cin, input);
+    if (input == "quit") { break; }
+    int x;
+    try {
+      x = std::stoi(input);
+    } catch(std::invalid_argument &) {
+      std::cout << "invalid input" << std::endl;
+      continue;
+    }
+    
+    match(x,
+      1, []() {std::cout << "The answer is one\n"; },
+      2, []() {std::cout << "The answer is two\n"; },
+      _x < 10, [](auto&& a) {std::cout << "The answer " << a << " is less than 10\n"; },
+      10 < _x < 20,	[](auto&& a) {std::cout << "The answer " << a  << " is between 10 and 20 exclusive\n"; },
+      _, []() {std::cout << "Did not match\n"; }
+    );
+  }
+
+  return 0;
+}

examples/yaml/CMakeLists.txt

@@ -0,0 +1,25 @@
+cmake_minimum_required(VERSION 3.14 FATAL_ERROR)
+
+# ---- Dependencies ----
+
+include(../../cmake/CPM.cmake)
+
+CPMAddPackage(
+  NAME yaml-cpp
+  GIT_REPOSITORY https://github.com/jbeder/yaml-cpp.git
+  # 0.6.2 uses depricated CMake syntax
+  VERSION 0.6.3                                  
+  # 0.6.3 is not released yet, so use the most recent commit
+  GIT_TAG 012269756149ae99745b6dafefd415843d7420bb 
+  OPTIONS
+    "YAML_CPP_BUILD_TESTS Off"
+    "YAML_CPP_BUILD_CONTRIB Off"
+    "YAML_CPP_BUILD_TOOLS Off"
+)
+
+# ---- Executable ----
+
+add_executable(CPMYamlExample "main.cpp")
+set_target_properties(CPMYamlExample PROPERTIES CXX_STANDARD 17)        
+target_link_libraries(CPMYamlExample yaml-cpp)
+

examples/yaml/main.cpp

@@ -0,0 +1,14 @@
+#include <yaml-cpp/yaml.h>
+#include <iostream>
+
+int main(int argc, char ** argv){
+  if (argc != 2) {
+    std::cout << "usage: " << argv[0] << " <path to yaml file>" << std::endl;
+    return 1;
+  }
+
+  YAML::Node config = YAML::LoadFile(argv[1]);
+  std::cout << "Parsed YAML:\n" << config << std::endl;
+
+  return 0;
+}

examples/yaml/monsters.yaml

@@ -0,0 +1,21 @@
+- name: Ogre
+  position: [0, 5, 0]
+  powers:
+    - name: Club
+      damage: 10
+    - name: Fist
+      damage: 8
+- name: Dragon
+  position: [1, 0, 10]
+  powers:
+    - name: Fire Breath
+      damage: 25
+    - name: Claws
+      damage: 15
+- name: Wizard
+  position: [5, -3, 0]
+  powers:
+    - name: Acid Rain
+      damage: 50
+    - name: Staff
+      damage: 3

tests/complex/CMakeLists.txt

@@ -1,55 +0,0 @@
-cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
-
-project(CPMTest)
-
-include(${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/CPM.cmake)
-
-# ignore locally installed projects for reproducable builds
-set(CPM_REMOTE_PACKAGES_ONLY ON CACHE INTERNAL "")
-
-# util library
-CPMAddPackage(
-  NAME LHC
-  GIT_REPOSITORY https://github.com/TheLartians/LHC.git
-  VERSION 0.7
-)
-
-# adding LHC again will be ignored as the package has already been added
-CPMAddPackage(
-  NAME LHC
-  GIT_REPOSITORY https://github.com/TheLartians/LHC.git
-  VERSION 0.1
-)
-
-# language bindings
-# uses git tag instead of version identifier
-# depends on visitor library that depends on Event library and LHC (ignored as already added)
-# configuration arguments passed via OPTIONS. these will all be set internally
-set(GLUE_ENABLE_LUA ON)
-CPMAddPackage(
-  NAME Glue
-  GIT_TAG 78af65625751ad15a42ca52b842863e85b5d2adc
-  GIT_REPOSITORY https://github.com/TheLartians/Glue.git
-  OPTIONS 
-    "GLUE_ENABLE_LUA ON"
-    "GLUE_BUILD_LUA ON"
-)
-
-# parser library 
-# depends on LHC (ignored as already added)
-CPMAddPackage(
-  NAME LarsParser
-  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
-  VERSION 1.8
-  OPTIONS 
-    "LARS_PARSER_BUILD_GLUE_EXTENSION ON"
-)
-
-# add executable
-set (CMAKE_CXX_STANDARD 17)
-add_executable(cpm-test test.cpp)
-target_link_libraries(cpm-test LHC LarsParser Glue)
-
-# tests
-enable_testing()
-add_test(cpm-test cpm-test)

tests/complex/test.cpp

@@ -1,52 +0,0 @@
-#include <lars/parser/extension.h>
-#include <lars/lua_glue.h>
-#include <stdexcept>
-
-int main() {
-  // create lua state
-  auto lua = lars::LuaState();
-  lua.open_libs();
-
-  // create extensions
-  lars::Extension extensions;
-
-  // add parser library to extension
-  extensions.add_extension("parser", lars::extensions::parser());
-
-  // connect parser extension to lua
-  extensions.connect(lua.get_glue());
-
-  // create a parser
-  lua.run(R"(
-    NumberMap = parser.Program.create()
-
-    NumberMap:setRule("Whitespace", "[ \t]")
-    NumberMap:setSeparatorRule("Whitespace")
-
-    NumberMap:setRuleWithCallback("Object", "'{' KeyValue (',' KeyValue)* '}'",function(e) 
-      local N = e:size()-1
-      local res = {}
-      for i=0,N do 
-        local a = e:get(i)
-        res[a:get(0):evaluate()] = a:get(1):evaluate() 
-      end
-      return res
-    end)
-
-    NumberMap:setRule("KeyValue", "Number ':' Number")
-
-    NumberMap:setRuleWithCallback("Number", "'-'? [0-9]+", function(e) return tonumber(e:string()); end)
-    
-    NumberMap:setStartRule("Object")
-  )");
-
-  // parse a string
-  lua.run("m = NumberMap:run('{1:3, 2:-1, 3:42}')");
-  
-  // check result
-  if (lua.get_numeric("m[1]") != 3) throw std::runtime_error("unexpected result");
-  if (lua.get_numeric("m[2]") != -1) throw std::runtime_error("unexpected result");
-  if (lua.get_numeric("m[3]") != 42) throw std::runtime_error("unexpected result");
-
-  return 0;
-}

tests/simple/CMakeLists.txt

@@ -1,21 +0,0 @@
-cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
-
-project(CPMTest)
-
-# add dependencies
-include(${CMAKE_CURRENT_SOURCE_DIR}/../../cmake/CPM.cmake)
-
-CPMAddPackage(
-  NAME LarsParser
-  GIT_REPOSITORY https://github.com/TheLartians/Parser.git
-  VERSION 1.7
-)
-
-# add executable
-set (CMAKE_CXX_STANDARD 17)
-add_executable(cpm-test test.cpp)
-target_link_libraries(cpm-test LarsParser)
-
-# tests
-enable_testing()
-add_test(cpm-test cpm-test)

tests/simple/test.cpp

@@ -1,27 +0,0 @@
-#include <lars/parser/generator.h>
-
-int main() {
-  lars::ParserGenerator<float> g;
-
-  // Define grammar and evaluation rules
-  g.setSeparator(g["Whitespace"] << "[\t ]");
-  g["Sum"     ] << "Add | Subtract | Product";
-  g["Product" ] << "Multiply | Divide | Atomic";
-  g["Atomic"  ] << "Number | '(' Sum ')'";
-  g["Add"     ] << "Sum '+' Product"    >> [](auto e){ return e[0].evaluate() + e[1].evaluate(); };
-  g["Subtract"] << "Sum '-' Product"    >> [](auto e){ return e[0].evaluate() - e[1].evaluate(); };
-  g["Multiply"] << "Product '*' Atomic" >> [](auto e){ return e[0].evaluate() * e[1].evaluate(); };
-  g["Divide"  ] << "Product '/' Atomic" >> [](auto e){ return e[0].evaluate() / e[1].evaluate(); };
-  g["Number"  ] << "'-'? [0-9]+ ('.' [0-9]+)?" >> [](auto e){ return stof(e.string()); };
-  g.setStart(g["Sum"]);
-
-  // Execute a string
-  float result = g.run("1 + 2 * (3+4)/2 - 3");
-
-  // validate result
-  if (result == 5) {
-    return 0;
-  } else {
-    return 1;
-  }
-}