I was recently asked by a friend to help him with customizing end-of-proof marks. Say that we are writing a textbook with theorems with proofs and example problems with solutions and that we want a usual after a proof, but, for example, a after a solution to a problem.

Probably the best way to accomplish this is by using the powerful `ntheorem`

package by Wolfgang May and Andreas Schedler (see its home page). But alas, I don’t usually use it (since I am used to `amsthm`

), which is a shame on me: `ntheorem`

seems to do all the work of `amsthm`

and much more. The only problem is that you have at least to skim through the documentation (which is well written and not too long) – I am quite busy now, but hopefully I will be able to read it in a few weeks’ time and write something about it here.

If you are an `amsthm`

-addict for some reason, there is also hope for you: just use the following quick-and-dirty solution (to be pasted in the preamble):

\newenvironment{solution}{% \proof[Solution]\def\qedsymbol{$\diamond$}% }{% \endproof }

What it does is:

- The newly-defined environment
`solution`

will launch the`proof`

environment whenever`\begin{solution}`

is put into the document. Roughly speaking,`\proof`

is (almost) the same as`\begin{proof}.`

- The
`\qedsymbol`

will be redefined into whatever we want (here, the ). Since we don’t use LaTeX’s`\newcommand`

, but plain TeX’s`\def`

, this redefinition is*local*, i.e., valid only within the`proof`

environment. - The
`\end{solution}`

is defined to be essentially the same as`\end{proof}`

; note that`\endproof`

is a “low-level version” (again, roughly speaking!) of`\end{proof}.`

Summing up: the main purpose of this construct is to teach people something (hopefully) interesting about how TeX and LaTeX works; for production purposes, `ntheorem`

is better.

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