Drop Boost dependency

Boost was only used for program option parsing. To avoid this huge
dependency, this commit replaces boost::program_options with cxxopts,
a header-only library with the same functionality.

cxxopts is added as a submodule, and Boost is removed from the
dependencies in the code and Travis configuration.

.ci/Dockerfile-arch-latest

@@ -3,7 +3,7 @@ FROM archimg/base-devel:latest
 ARG toolchain
 
 RUN pacman -Sy
-RUN pacman -S --noconfirm boost cmake git ninja re2c
+RUN pacman -S --noconfirm cmake git ninja re2c
 RUN if [ "${toolchain}" = "clang" ]; then pacman -S --noconfirm clang; fi
 
 VOLUME /app

.ci/Dockerfile-ubuntu-18.04

@@ -3,7 +3,7 @@ FROM ubuntu:18.04
 ARG toolchain
 
 RUN apt-get update
-RUN apt-get install -y libboost-all-dev cmake git ninja-build re2c
+RUN apt-get install -y cmake git ninja-build re2c
 RUN if [ "${toolchain}" = "gcc" ]; then apt-get install -y g++; fi
 RUN if [ "${toolchain}" = "clang" ]; then apt-get install -y clang; fi
 

.gitmodules

@@ -4,3 +4,6 @@
 [submodule "lib/catch"]
 	path = lib/catch
 	url = https://github.com/catchorg/Catch2
+[submodule "lib/cxxopts"]
+	path = lib/cxxopts
+	url = https://github.com/jarro2783/cxxopts

README.md

@@ -16,7 +16,7 @@ With the option `--simplify`, output formulas are simplified by applying several
 
 ## Building
 
-`anthem` requires [CMake](https://cmake.org/) and [Boost](http://www.boost.org/) for building.
+`anthem` requires [CMake](https://cmake.org/) for building.
 After installing the dependencies, `anthem` is built with a C++17 compiler (GCC ≥ 7.3 or clang ≥ 5.0).
 
 ```bash

app/CMakeLists.txt

@@ -1,7 +1,5 @@
 set(target anthem-app)
 
-find_package(Boost 1.55.0 COMPONENTS program_options system filesystem REQUIRED)
-
 file(GLOB core_sources "*.cpp")
 file(GLOB core_headers "*.h")
 
@@ -11,11 +9,10 @@ set(sources
 )
 
 set(includes
-	${Boost_INCLUDE_DIRS}
+	${PROJECT_SOURCE_DIR}/lib/cxxopts/include
 )
 
 set(libraries
-	${Boost_LIBRARIES}
 	anthem
 )
 

app/main.cpp

@@ -1,6 +1,6 @@
 #include <iostream>
 
-#include <boost/program_options.hpp>
+#include <cxxopts.hpp>
 
 #include <anthem/AST.h>
 #include <anthem/Context.h>
@@ -10,63 +10,70 @@ int main(int argc, char **argv)
 {
 	anthem::Context context;
 
-	namespace po = boost::program_options;
+	cxxopts::Options options("anthem", "Translate ASP programs to the language of first-order theorem provers.");
 
-	po::options_description description("Allowed options");
-	description.add_options()
-		("help,h", "Display this help message")
-		("version,v", "Display version information")
-		("input,i", po::value<std::vector<std::string>>(), "Input files")
-		("simplify,s", po::bool_switch(&context.performSimplification), "Simplify the output")
-		("complete,c", po::bool_switch(&context.performCompletion), "Perform completion")
-		("color", po::value<std::string>()->default_value("auto"), "Colorize output (always, never, auto)")
-		("parentheses", po::value<std::string>()->default_value("normal"), "Parenthesis style (normal, full)")
-		("log-priority,p", po::value<std::string>()->default_value("warning"), "Log messages starting from this priority (debug, info, warning, error)");
+	options.add_options()
+		("h,help", "Display this help message")
+		("v,version", "Display version information")
+		("i,input", "Input files", cxxopts::value<std::vector<std::string>>())
+		("s,simplify", "Simplify the output")
+		("c,complete", "Perform completion")
+		("color", "Colorize output (always, never, auto)", cxxopts::value<std::string>()->default_value("auto"))
+		("parentheses", "Parenthesis style (normal, full)", cxxopts::value<std::string>()->default_value("normal"))
+		("p,log-priority", "Log messages starting from this priority (debug, info, warning, error)", cxxopts::value<std::string>()->default_value("info"));
 
-	po::positional_options_description positionalOptionsDescription;
-	positionalOptionsDescription.add("input", -1);
-
-	po::variables_map variablesMap;
+	options.parse_positional("input");
+	options.positional_help("[<input file...>]");
 
 	const auto printHelp =
 		[&]()
 		{
-			std::cout
-				<< "Usage: anthem [options] file..." << std::endl
-				<< "Translate ASP programs to the language of first-order theorem provers." << std::endl << std::endl
-				<< description;
+			std::cout << options.help();
 		};
 
+	bool help;
+	bool version;
+	std::vector<std::string> inputFiles;
+	std::string colorPolicyString;
+	std::string parenthesisStyleString;
+	std::string logPriorityString;
+
 	try
 	{
-		po::store(po::command_line_parser(argc, argv)
-			.options(description)
-			.positional(positionalOptionsDescription)
-			.run(),
-			variablesMap);
-		po::notify(variablesMap);
+		const auto parseResult = options.parse(argc, argv);
+
+		help = (parseResult.count("help") > 0);
+		version = (parseResult.count("version") > 0);
+
+		if (parseResult.count("input") > 0)
+			inputFiles = parseResult["input"].as<std::vector<std::string>>();
+
+		context.performSimplification = (parseResult.count("simplify") > 0);
+		context.performCompletion = (parseResult.count("complete") > 0);
+		colorPolicyString = parseResult["color"].as<std::string>();
+		parenthesisStyleString = parseResult["parentheses"].as<std::string>();
+		logPriorityString = parseResult["log-priority"].as<std::string>();
 	}
-	catch (const po::error &e)
+	catch (const std::exception &exception)
 	{
-		context.logger.log(anthem::output::Priority::Error) << e.what();
+		context.logger.log(anthem::output::Priority::Error) << exception.what();
+		context.logger.errorStream() << std::endl;
 		printHelp();
 		return EXIT_FAILURE;
 	}
 
-	if (variablesMap.count("help"))
+	if (help)
 	{
 		printHelp();
 		return EXIT_SUCCESS;
 	}
 
-	if (variablesMap.count("version"))
+	if (version)
 	{
 		std::cout << "anthem version 0.1.7-git" << std::endl;
 		return EXIT_SUCCESS;
 	}
 
-	const auto colorPolicyString = variablesMap["color"].as<std::string>();
-
 	if (colorPolicyString == "auto")
 		context.logger.setColorPolicy(anthem::output::ColorStream::ColorPolicy::Auto);
 	else if (colorPolicyString == "never")
@@ -81,22 +88,18 @@ int main(int argc, char **argv)
 		return EXIT_FAILURE;
 	}
 
-	const auto parenthesisStyle = variablesMap["parentheses"].as<std::string>();
-
-	if (parenthesisStyle == "normal")
+	if (parenthesisStyleString == "normal")
 		context.parenthesisStyle = anthem::ast::ParenthesisStyle::Normal;
-	else if (parenthesisStyle == "full")
+	else if (parenthesisStyleString == "full")
 		context.parenthesisStyle = anthem::ast::ParenthesisStyle::Full;
 	else
 	{
-		context.logger.log(anthem::output::Priority::Error) << "unknown parenthesis style “" << parenthesisStyle << "”";
+		context.logger.log(anthem::output::Priority::Error) << "unknown parenthesis style “" << parenthesisStyleString << "”";
 		context.logger.errorStream() << std::endl;
 		printHelp();
 		return EXIT_FAILURE;
 	}
 
-	const auto logPriorityString = variablesMap["log-priority"].as<std::string>();
-
 	try
 	{
 		const auto logPriority = anthem::output::priorityFromName(logPriorityString.c_str());
@@ -112,11 +115,8 @@ int main(int argc, char **argv)
 
 	try
 	{
-		if (variablesMap.count("input"))
-		{
-			const auto &inputFiles = variablesMap["input"].as<std::vector<std::string>>();
+		if (!inputFiles.empty())
 			anthem::translate(inputFiles, context);
-		}
 		else
 			anthem::translate("std::cin", std::cin, context);
 	}

lib/cxxopts

@@ -0,0 +1 @@
+Subproject commit 8893afe13cc47dd0be4f25b5ae491e652c146098