# [OS X TeX] Latex symbol for "define equal"

David Derbes loki at uchicago.edu
Mon Aug 20 00:43:55 CEST 2018

I and several colleagues just finished editing a 1200 page manuscript, LaTeX’d lectures of the great Sidney Coleman on quantum field theory. One of the colleagues was the well-known physicist author David Griffiths, who earned his doctorate under Coleman. He championed \equiv for “defined as”, and I think that is pretty standard in physics. It appears perhaps two dozen times in the Coleman lectures.

I’m an old Pascal programmer (there are probably not that many young Pascal programmers :-) ) and while I love :=, I don’t see it catching on as “defined as”, notwithstanding the impeccable logic of JMaF. I have never seen it used that way in physics (but that doesn’t mean it hasn’t been).

David Derbes
U of Chicago Lab Schools

On Aug 19, 2018, at 17:05, Josep Maria Font <jmfont at ub.edu> wrote:

> In logic and universal algebra, and in general in disciplines where the equals sign = can be not just a symbol but a mathematical object by itself, some people (including me :-) find it useful to have a special equals symbol which means "equal by definition". I have been using := , and for this the "mathtools" package offers a fine solution, the macro \coloneqq, which places the : symmetrically wrt the axis of the = symbol (something you do not obtain by just writing := !).
>
> And I find this usage somehow comparable to the "assignment" usage of programming languages; only that here we are "assigning a meaning" to a previously void symbol or complex of symbols.
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> JMaF
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>> El 19 /08/18, a les 23:50, R Martinez <rm.tech at mac.com> va escriure:
>>
>> I believe that Don Knuth favors using the plain equals sign = for everything including definitions. I read it somewhere but can’t recall the source. One bit of evidence is that in his book “Concrete Mathematics” the floor and ceiling functions are defined using the equals sign (1989 edition, page. 67).
>>
>> Raul Martinez
>>
>>> On Aug 19, 2018, at 3:28 AM, Vic Norton <vic at norton.name> wrote:
>>>
>>>
>>>> On Aug 18, 2018, at 10:01 PM, Art Werschulz <agw at comcast.net> wrote:
>>>>
>>>> The centercolon and mathtools LaTeX packages are used to fix symmetry issues with := .
>>>
>>> In Pascal and Algol := is the assignment operator. The phrase x := 2 means “set x equal to 2". I personally would avoid using := for any other purpose in LaTeX.
>>> —
>>> Vic
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