RE: typo in frame.el

[Drew Adams]

How about we use "<=>", conventionally, in doc strings, but we also explain
this convention in the Emacs manual, for those who have never seen it? If we
adopt such a convention, then we should perhaps also conventionally use "=>"
for "implies" ("only if") and "<=" for "if".

(If you don't enjoy semantic nitpicking, hit the delete key now.)

In "precisely when", the key word, which makes it equivalent to "iff", is
"precisely". If you drop it, then you're back to just "if": "when", by
itself, means just "if" - that is:

  "a when b" <=> "a if b" <=> "b only if a" <=> "if b then a"

I think "iff" is much more common, in English technical writing, than
"precisely when". ("<=>" is more common than "iff" in math: it is not tied
to a natural language.)

Also, it is fairly common in programming to use "when" to indicate one or
both of these (as opposed to just logical implication):

 - temporal relation ("at the same time as")
 - condition for a temporal sequence of actions/events

For example, in Common Lisp, "when" is used stylistically to introduce a
conditional sequence of actions (with side effects).

 - Drew

-----Original Message-----
From: address@hidden
[mailto:address@hidden Behalf Of
Simon Josefsson
Sent: Friday, April 09, 2004 1:22 PM
To: address@hidden
Subject: Re: typo in frame.el


Alex Schroeder <address@hidden> writes:

> Hiroshi Fujishima <address@hidden> writes:
>
>> -With a numeric argument, turn blinking cursor mode on iff ARG is
positive.
>> +With a numeric argument, turn blinking cursor mode on if ARG is
positive.
>
> For mathematicians, "iff" is an abbreviation for "if and only
> if"...  So it is not a typo, I suppose.  I think that should avoid the
> use of such abbreviations in Emacs documentation, however, since not
> all our users come from an English/science background.

I prefer "precisely when" instead of "if and only if".  Sometimes,
even the "precisely" can be omitted.  Less technobabbly.  Alas,
changing "iff" into "when" can make a documentation string line too
long.  Confusion regarding "iff" is a reoccurring theme, so it might
make sense to do something about it.

(Kudos to my algebra professor, who introduced me to p.w., although
only for Swedish.  But I think it works as well in English.  Any
native speaker who disagree?)



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