created a header-only version (see issue #16)

Makefile.am

+.PHONY: header_only
+
+# the order is important: header before other sources
+CORE_SOURCES = src/json.h src/json.cc
+
 noinst_PROGRAMS = json_unit json_parser
 
 FLAGS = -Wall -Wextra -pedantic -Weffc++ -Wcast-align -Wcast-qual -Wctor-dtor-privacy -Wdisabled-optimization -Wformat=2 -Winit-self -Wmissing-declarations -Wmissing-include-dirs -Wold-style-cast -Woverloaded-virtual -Wredundant-decls -Wshadow -Wsign-conversion -Wsign-promo -Wstrict-overflow=5 -Wswitch -Wundef -Wno-unused -Wnon-virtual-dtor -Wreorder
 
-json_unit_SOURCES = src/json.cc src/json.h test/catch.hpp test/json_unit.cc
+json_unit_SOURCES = $(CORE_SOURCES) test/catch.hpp test/json_unit.cc
 json_unit_CXXFLAGS = $(FLAGS) -std=c++11
 json_unit_CPPFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/test -Dprivate=public
 
-json_parser_SOURCES = src/json.cc src/json.h benchmark/parse.cc
+json_parser_SOURCES = $(CORE_SOURCES) benchmark/parse.cc
 json_parser_CXXFLAGS = -O3 -std=c++11 -flto
 json_parser_CPPFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/benchmark
 
@@ -26,4 +31,9 @@ pretty:
 	   $(SOURCES)
 
 parser:
-	make CXXFLAGS="" json_parser
\ No newline at end of file
+	make CXXFLAGS="" json_parser
+
+header_only/json.h: $(CORE_SOURCES)
+	cat $(CORE_SOURCES) | $(SED) 's/#include "json.h"//' > header_only/json.h
+
+BUILT_SOURCES = header_only/json.h

README.md

@@ -26,7 +26,7 @@ Other aspects were not so important to us:
 
 ## Integration
 
-All you need to do is add
+The two required source files are in the `src` directory. All you need to do is add
 
 ```cpp
 #include "json.h"
@@ -37,6 +37,8 @@ using json = nlohmann::json;
 
 to the files you want to use JSON objects. Furthermore, you need to compile the file `json.cc` and link it to your binaries. Do not forget to set the necessary switches to enable C++11 (e.g., `-std=c++11` for GCC and Clang).
 
+If you want a single header file, use the `json.h` file from the `header_only` directory.
+
 ## Examples
 
 Here are some examples to give you an idea how to use the class.

configure.ac

@@ -5,6 +5,7 @@ AM_INIT_AUTOMAKE([foreign subdir-objects])
 AM_SILENT_RULES([yes])
 
 AC_PROG_CXX
+AC_PROG_SED
 
 AC_CONFIG_FILES(Makefile)
 AC_OUTPUT