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From: ark@alice.UucP (Andrew Koenig)
Newsgroups: net.lang.c
Subject: Re: ANSI 'C'.
Message-ID: <4600@alice.UUCP>
Date: Thu, 21-Nov-85 15:37:40 EST
Article-I.D.: alice.4600
Posted: Thu Nov 21 15:37:40 1985
Date-Received: Sat, 23-Nov-85 01:38:44 EST
References: <171@watmath.UUCP>
Organization: Bell Labs, Murray Hill
Lines: 14

> The standard obviously didn't put much thought into anything related to
> times.  They define type "time_t" as an arithmetic type that represents
> the time, and then define a difftime(time_t time1,time_t time2) that
> computes the difference between these two arithmetic values.  Why the
> function?  Does the standard have a new arithmetic type on which the
> operation of subtraction is not allowed?
> And then they define a function gmtime(const time_t *timer) that takes
> a pointer to the arithmetic value, which it is not going to change anyway.
> Why not just take the value itself instead of the pointer?

gmtime takes a pointer rather than the value itself for historical
reasons.  Before C had long integers, gmtime() took an array of
two integers as its argument.  Since C does not pass arrays by value,
gmtime() actually saw a pointer.