Re: [Scheme-reports] [r6rs-discuss] Date and time arithmetic library proposal for R7RS large Scheme

[John Cowan <cowan@x>]

Christopher Chittleborough scripsit:

> (chronology-with-time-zone CHRONOLOGY TIMEZONE)
>   Presumably a "time zone name" is a string. Say so explicitly?

I actually do say what it can be: an offset in minutes from UTC,
a string from the TZ database, or an implementation-defined alternative.

> (date->instant DATE)
>   What happens if there is not enough info in DATE to uniquely
>   determine an instant? Signal an error? Return #f?

Added "otherwise return #f".

> (date-field date FIELDNAME)
>   Presumably FIELDNAME can be a symbol. Can it also be a string?

That would require an extra lookup at run time.  I think symbols are sufficient.

> (date-increment date fieldname increment)
>   Suggestion: instead of talking about incrementing the specified
>   *field*, put it in terms of incrementing the *date* by the units
>   (month/day/hour/...) corresponding to fieldname. Something like:
>     Constructs and returns a new date object which is later than DATE by
>     INCREMENT of the units specified by FIELDNAME (earlier if INCREMENT
>     negative). For example, (date-increment date 'day-of-month 7) adds
>     one week.

Excellent wording; adopted.

> The 'century' values in the ISO chronology don't seem right.
> If 1965 AD has century=19 in ISO, then 33 AD must have century=0
> so 43 BC would have century=-1, not 0.

Fixed.

-- 
So they play that [tune] on                     John Cowan
their fascist banjos, eh?                       cowan@x
        --Great-Souled Sam                      http://www.ccil.org/~cowan

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