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## Re: inverse of float-time?

**From**: |
Paul Eggert |

**Subject**: |
Re: inverse of float-time? |

**Date**: |
Tue, 17 Sep 2013 14:10:22 -0700 |

**User-agent**: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130805 Thunderbird/17.0.8 |

On 09/17/13 13:03, Sam Steingold wrote:
>* float-time should be either deprecated or granted equal rights :-)*
It should be deprecated.
float-time is based on assumptions that go back to the Good
Old Days, when time stamps typically were 32-bit signed
integer counts of seconds, possibly with an additional
microseconds count. Under these assumptions float-time
doesn't lose information on typical platforms with IEEE
doubles, which are just barely large enough.
Nowadays, though, time_t is often 64 bits, and timestamps
are typically nanosecond resolution. IEEE doubles can't
represent these time stamps without losing information, so
float-time generates results with rounding errors.
If we could assume Guile, I suppose we could represent these modern
time stamps exactly, using fractions. That may be a good
way to go in the future. It'd be a lot more convenient than
the current list-of-integers representation.
>* So, what is the official use case for float-time?*
>* When one would use it instead of time-date?*
I assume that it was put in to make it convenient to compare
or subtract time stamps, or to add a time stamp to a seconds
count. (You added float-time back in 2000, so you should
know better than I. :-) These days, one should use
time-less-p, time-subtract, and time-add, as they shouldn't
have rounding errors.

**inverse of float-time?**, *Sam Steingold*, `2013/09/11`
**Re: inverse of float-time?**, *Paul Eggert*, `2013/09/11`
**Re: inverse of float-time?**, *Sam Steingold*, `2013/09/11`
**Re: inverse of float-time?**, *Leo Liu*, `2013/09/11`
**Re: inverse of float-time?**, *Sam Steingold*, `2013/09/11`
**Re: inverse of float-time?**, *Paul Eggert*, `2013/09/12`
**Re: inverse of float-time?**, *Ulrich Mueller*, `2013/09/12`
**Re: inverse of float-time?**, *Sam Steingold*, `2013/09/17`
**Re: inverse of float-time?**,
*Paul Eggert* **<=**

**Re: inverse of float-time?**, *SAKURAI Masashi*, `2013/09/11`