#
# = Error Handling
#
# == Error codes
# The GSL routines report an error whenever they cannot perform the task
# requested of them. For example, a root-finding function would return a
# non-zero error code if could not converge to the requested accuracy,
# or exceeded a limit on the number of iterations. Situations like this
# are a normal occurrence when using any mathematical library and
# you should check the return status of the functions that you call.
#
# Whenever a routine reports an error the return value specifies the type of error.
# The return value is analogous to the value of the variable errno in the C library.
# The caller can examine the return code and decide what action to take, including
# ignoring the error if it is not considered serious.
#
# The error code numbers in GSL as GSL_EDOM are defined in Ruby/GSL
# as Ruby constants under the GSL module. Here are some of them:
# * GSL::EDOM - Domain error; used by mathematical functions when an
# argument value does not fall into the domain over which the function is
# defined (like EDOM in the C library)
# * GSL::ERANGE - Range error; used by mathematical functions when the
# result value is not representable because of overflow or underflow
# (like ERANGE in the C library)
# * GSL::ENOMEM - No memory available. The system cannot allocate more
# virtual memory because its capacity is full (like ENOMEM in the
# C library). This error is reported when a GSL routine encounters problems
# when trying to allocate memory with malloc.
# * GSL::EINVAL - Invalid argument. This is used to indicate various
# kinds of problems with passing the wrong argument to a library function
# (like EINVAL in the C library).
#
# == Error handler
# In Ruby/GSL, the default GSL error handler is replaced by an other one which calls
# rb_raise(). Thus whenever a GSL routine reports a fatal error,
# a Ruby Exception is generated.
#
# ---
# * GSL::set_error_handler(proc)
# * GSL::set_error_handler { |reason, file, line, errno| ... }
#
# This replaces the Ruby/GSL default error handler by a user-defined handler
# given by a Proc object proc or a block.
#
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