Re: Unspecified?

[Andy Wingo]

Hey Maciek,

On Fri 14 Nov 2008 11:38, "Maciek Godek" <address@hidden> writes:

> Hey all yoh!
> Is there any "official" way to check whether or not
> a function returns a (specified) value?

Yes and no; R5RS has this to say:

    If the value of an expression is said to be "unspecified," then the
    expression must evaluate to some object without signalling an error,
    but the value depends on the implementation; this report explicitly
    does not say what value should be returned.

In practice, in all situations in which R5RS defines a result as
unspecified, those values will be `eq?' to `(if #f #f)'.

> but I find it kinda surprising that these are not available
> by default in the system.

Odd, yes. We inherit this oddity from Scheme.

Andy
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