Raising exceptions from external code

The following macros explicitly raise certain errors, immediately returning to Scheme 48. Raising an exception performs all necessary clean-up actions to properly return to Scheme 48, including adjusting the stack of protected variables.

• s48_raise_scheme_exception(int type, int nargs, ...)

s48_raise_scheme_exception is the base procedure for raising exceptions. type is the type of exception, and should be one of the S48_EXCEPTION_...constants defined in scheme48arch.h. nargs is the number of additional values to be included in the exception; these follow the nargs argument and should all have type s48_value. s48_raise_scheme_exception never returns.

The following procedures are available for raising particular types of exceptions. Like s48_raise_scheme_exception these never return.

• s48_raise_argument_type_error(s48_value)
• s48_raise_argument_number_error(int nargs, int min, int max)
• s48_raise_range_error(long value, long min, long max)
• s48_raise_closed_channel_error()
• s48_raise_os_error(int errno)
• s48_raise_out_of_memory_error()

An argument type error indicates that the given value is of the wrong type. An argument number error is raised when the number of arguments, nargs, should be, but isn't, between min and max, inclusive. Similarly, a range error indicates that value is not between between min and max, inclusive.

The following macros raise argument type errors if their argument does not have the required type. S48_CHECK_BOOLEAN raises an error if its argument is neither #t or #f.

• void S48_CHECK_BOOLEAN(s48_value)
• void S48_CHECK_SYMBOL(s48_value)
• void S48_CHECK_PAIR(s48_value)
• void S48_CHECK_STRING(s48_value)
• void S48_CHECK_INTEGER(s48_value)
• void S48_CHECK_CHANNEL(s48_value)
• void S48_CHECK_BYTE_VECTOR(s48_value)
• void S48_CHECK_RECORD(s48_value)
• void S48_CHECK_SHARED_BINDING(s48_value)

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