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2012-03-30 00:58:49
4Documented mixed exactness in complex numbers.history

MIT Scheme now has support for positive and negative infinities and for signaling (the default) and non-signaling NaNs. I'm documenting this here because the MIT Scheme manual doesn't yet describe these features, and having them here might be useful if we discuss this stuff in WG2.

The printed representations are #[+inf], #[-inf], and #[NaN], and are not readable.

To disable signaling: (flo:ignoring-exception-traps thunk). For example:

(flo:ignoring-exception-traps (lambda () (let* ((i (* 1.0e200 1.0e200)) (n (- i i))) (list i (- i) n)))) ;Value 13: (#[+inf] #[-inf] #[NaN])

Different NaN values are not eqv?.

Complex numbers can have one exact part and one inexact part.

These procedures are available for manipulating the floating-point environment:

flo:nan? flo:raise-exceptions! flo:restore-exception-flags! flo:rounding-mode flo:rounding-modes flo:save-exception-flags flo:set-environment! flo:set-rounding-mode! flo:set-trapped-exceptions! flo:significand-digits-base-2 flo:significand-digits-base-10 flo:supported-exceptions flo:test-exception-flags flo:test-exceptions flo:trap-exceptions! flo:trappable-exceptions flo:trapped-exceptions flo:untrap-exceptions! flo:update-environment! flo:with-default-environment flo:with-exceptions-trapped flo:with-exceptions-untrapped flo:with-rounding-mode flo:with-trapped-exceptions