Re: [PATCH] Don't ignore write failure from git-diff, git-log, etc.

From: Junio C Hamano <junkio@cox.net>
Date: May 26, 2007, 17:27 UTC
Message-ID: <7vk5uvjy0g.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <alpine.LFD.0.98.0705260910220.26602@woody.linux-foundation.org>

Linus Torvalds <torvalds@linux-foundation.org> writes:

Show 17 quoted lines

> Also, PLEASE don't do this:
>
>> +		if (0 <= fcntl(fileno (stdout), F_GETFD)
>
> That's totally unreadable to any normal human.
>
> You don't say "if zero is smaller or equal to X". You say "if X is larger 
> than or equal to zero". Stop messing with peoples minds, dammit!
>
> Anybody who thinks that code like this causes fewer errors is just fooling 
> himself. It causes *more* bugs, because people have a harder time reading 
> it.
>
> Maybe you and Junio have taught yourself bad manners, but you're a tiny 
> tiny part of humanity or the development community. Junio can do it just 
> because while he's just a single person, he's a big part of the git coding 
> base, but anybody else who does it should just be shot.

Whew, that is a blast from the past.

cf. http://thread.gmane.org/gmane.comp.version-control.git/3903/focus=3906

 (1) Maybe Jim was just being nice, trying to make the code look
     like surrounding code;

 (2) Maybe Jim and the person I learned the style from worked
     together for a long time and they picked it up from the
     same source;

 (3) Maybe I am not alone, and it is not native language -
     mother tongue issue as some suspected in the quoted thread.

In any case, I think my recent code have much less "textual order should reflect actual order" convention than before, because I have been forcing myself to say aloud "if X is larger" or "if X is smaller" before writing my comparisons, in order to match the "peoples minds" expectation you mentioned above.

This initially slowed me down and made my head hurt quite a bit, and sometimes it still does.

Once you learn to _visualize_ the ordering relationship in "X op Y" by relying on "op" being always < or <=, you will get the "number line" pop in your head whenever you see a comparision expression, without even having to think about it, and you "see" X and Y on the number line:

        ... -2        -1         0         1         2  ...  
    ---------+---------+---------+---------+---------+---------
    true:                        0   <=  fcntl(...)

        ... -2        -1         0         1         2  ...  
    ---------+---------+---------+---------+---------+---------
    false:    (0 <= fcntl(...))

What the comparison is doing comes naturally to you, without even having to translate it back to human language "X is larger (or smaller) than this constant". The ordering is right there, in front of your eyes, before you vocalize it.

In a sense, just like it is hard to go back from git to CVS (or it is hard to go back to not knowing the power of the index), it is very hard to go back once you learn to do this.