What does the "\" operator mean in the above context?
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1For sets $A$ and $B$, $A\backslash B = {x \in A : x \not \in B}$. Effectively it means $A$ without $B$. – GiantTortoise1729 Jun 26 '15 at 19:53
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1Cool thanks, could you phrase this in an answer so I can upvote and give you credit? – Carlo del Mundo Jun 26 '15 at 19:54
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By the way, division is a forward-slash, not a backwards-slash. – anon Jun 26 '15 at 19:55
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1@GiantTortoise1729 : One should write $A\setminus B$ rather than $A\backslash B$. \setminus provides proper spacing, as do things like $+$ and $-$ and $\times$, since it's a binary operator. ${}\qquad{}$ – Michael Hardy Jun 26 '15 at 19:57
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@MichaelHardy: Actually, $A\setminus B$ is overspaced for just these characters, and $A\backslash B$ looks better. However, the spacing of \setminus is better when the sets are complicated constructions, which is often the case. – John Bentin Jun 26 '15 at 22:16
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@JohnBentin : Which of these do you think is better: $A+B$ or $A{+}B$? ${}\qquad{}$ – Michael Hardy Jun 26 '15 at 22:41
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@MichaelHardy: The former: it's standard, and the laterally extensive plus sign is better at this spacing (although my taste would be for slightly narrower spacing). In the olden days, when mathematics was set by typesetters, the best typesetters would vary the spacing around operators according to context. Now, in LaTex, it's "one size fits all" for simplicity. – John Bentin Jun 27 '15 at 13:59
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@JohnBentin : LaTeX isn't one-size-fits-all. In LaTeX, the spacing depends on the context. I suspect that is true of MathJax as well. (What is used here is obviously not LaTeX, but people keep calling it that.) – Michael Hardy Jun 27 '15 at 16:21
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QUOTE the best typesetters would vary the spacing around operators according to context. Now, in LaTex, it's "one size fits all" END QUOTE. That is utter nonsense. You can't have used LaTeX much if you think it's not context-dependent in LaTeX. – Michael Hardy Jun 27 '15 at 16:23