Logging

only if the condition is false (or 0, or NULL) something will be logged
there are no log levels
the macro will throw an std::exception if the condition was not met
this normally terminates the running program

@Add(includes)
	#include @s(<iostream>)
	#include @s(<exception>)
@End(includes)

std::cerr from @s(<iostream>) is used to write log messages
a standard exception from @s(<exception>) is used to indicate failed conditions

@Def(frag prereqs)
	#define ASSERT(COND) \
		if (! (COND)) { \
			@mul(log preamble) \
			@mul(log newline) \
			@mul(throw) \
		}
@End(frag prereqs)

the plain @f(ASSERT) macro does nothing if the condition evaluates to true
otherwise the position of the line with the assertion will be written
and a small message
no details are given and the line is terminated with a newline
then an exception is raised

@Add(frag prereqs)
	#define ASSERT_MSG(COND, MSG) \
		if (! (COND)) { \
			@mul(log preamble) \
			std::cerr << ": " << MSG; \
			@mul(log newline) \
			@mul(throw) \
		}
@End(frag prereqs)

the macro @f(ASSERT_MSG) has an additional argument that the macro writes after the preamble
MSG can be multiple parameters concatenated by <<

@Add(frag prereqs)
	#define WARN_MSG(MSG) \
		std::cerr << __FILE__ << ':' << \
			__LINE__ << ' '; \
		std::cerr << MSG; \
		@mul(log newline)
@end(frag prereqs)

a warning writes the same message, as an assertion
but it will not terminate the program

@def(log preamble) \
	std::cerr << \
		__FILE__ << ':' << __LINE__ << \
		' ' << #COND << " FAILED"; \
@end(log preamble)

the preamble starts with the position in the format filename:line
this is recognized by a number of editors
afterwards a short error message is written

@def(log newline) \
	std::cerr << '\n'; \
@end(log newline)

a simple newline terminates an error message

@def(throw) \
	throw std::exception(); \
@end(throw)

the assert macros throw a generic std::exception if the condition was not met