Text Formatting ⇒ Definition of non-trivial numerical Values

[svend_tveskaeg]

Hi all.

Inspired by Clemens' answer in siunitx | Calculated Value in physical Quantities, I would like to define numbers like

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\def\horse{\the\numexpr sqrt(3)-sqrt(2) \relax}

I.e., involving square roots.

I have tried

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\def\horse{\the\numexpr 3^(1/2)-2^(1/2) \relax}

but that is not correct. (Therefore, it would also be nice to know how to define expressions involving powers.)

How do I do this?

Furthermore, why does the following not produce any output for \area?

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\documentclass{article}

\usepackage{auto-pst-pdf,pstricks-add}
\usepackage{siunitx}

\begin{document}

\begin{figure}
\def\minimum{0 }
\def\maximum{10 }
\def\length{\the\numexpr \maximum-\minimum \relax}
\def\PI{3.1415926535897932384626 }
\def\area{\the\numexpr 1/2*(\PI-2)*\length*\length \relax}
 \centering
  \begin{pspicture}(\maximum,\maximum)
   \pnode(!\minimum \minimum){A}
   \pnode(!\minimum \maximum){B}
   \pnode(!\maximum \maximum){C}
   \pnode(!\maximum \minimum){D}
   \pspolygon(A)(B)(C)(D)
   \psarc(!\maximum \minimum){!\length}{90}{180}
   \psarc(!\minimum \maximum){!\length}{270}{360}
  \psset{offset=12pt,nrot=:U}
   \psIntersectionPoint(A)(C)(B)(D){Y}
   \rput(Y){$A = \SI{\area}{\square\cm}$}
   \pcline{|-|}(B)(C)
   \ncput*{\SI{\length}{\cm}}
   \pcline{|-|}(C)(D)
   \ncput*{\SI{\length}{\cm}}
  \end{pspicture}
\end{figure}

\end{document}

Thank you in advance!

[localghost]

Actually TeX is not a calculator, at least not a good one. Its calculation capabilities are enhanced with the upcoming and at the moment experimental LaTeX3 programming language. As far as I know, the »l3fp« package from the l3kernel bundle offers some more convenient structures. And perhaps the mathematical engine of the pgf package comes also into question.


Thorsten

[cgnieder]

I'm unsure why your \area fails, but »l3fp« actually is a good choice as an alternative:

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\documentclass{article}
\usepackage{expl3}

\ExplSyntaxOn
\cs_new_eq:NN \calculate \fp_eval:n
\ExplSyntaxOff

\def\minimum{0 }
\def\maximum{10 }
\def\length{\calculate{\maximum-\minimum}}
\def\horse{\calculate{3^.5 - 2^.5}}
\def\area{\calculate{1/2*(pi-2)*\length*\length}}
\begin{document}

\noindent
\horse\\
\length\\
\area

\end{document}

Further reading: interface3

Regards

[CrazyHorse]

Inspired by Clemens' answer in siunitx | Calculated Value in physical Quantities, I would like to define numbers like

it is a bit tricky but possible:

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\def\minimum{0 }
\def\maximum{10 }
\def\length{\the\numexpr \maximum-\minimum \relax}
\def\PI{3.1415923}
\newlength\lTMP
\lTMP=\PI pt
\advance \lTMP by -2pt
\lTMP=\length\lTMP 
\lTMP=\length\lTMP 
\lTMP=0.5\lTMP
\makeatletter \edef\area{\strip@pt\lTMP} \makeatother

[svend_tveskaeg]

@Thorsten, Clemens, and Herbert: Thank you very much!

One last thing regarding this: How do I get only two decimals accuracy, using Herbert's implementation?

I tried

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\rput(Y){$A \approx \SI[round-precision=2]{\areal}{\square\cm}$}

but then I (still) get

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A \approx 57,07932

instead of

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A \approx 57,08

[cgnieder]

You need to set siunitx' round-mode which is off as default:

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\sisetup{round-mode=places}

Regards

[svend_tveskaeg]

I see. Thank you!