在 \pgfmathparse 或 \SI 中使用 \pgfmathprintnumberto 生成的宏

Question

为了演示，这里有一个 MWE：

\documentclass[a4paper,titlepage]{article}

\usepackage{pgf}
\usepackage{siunitx}

\begin{document}
    \pgfmathparse{1 + 1}
    \pgfmathprintnumberto{\pgfmathresult}{\calcResult}

    % Both this line
    \pgfmathparse{\calcResult + 1}

    % and this one
    \SI{\calcResult}{\cm}

    % do not work.
\end{document}

我看到的错误是：

! Package PGF Math Error: Unknown operator `$' or `$2' (in '$2$+ 1').

! siunitx error: "invalid-token-in-number"
!
! Invalid token '$' in numerical input.

! siunitx error: "invalid-number"
!
! Invalid numerical input '$2$'.
!
! See the siunitx documentation for further information.

Answer 1

\pgfmathprintnumberto{2}{\calcResult}结果为$2$。您可以\pgfmathsetmacro{\calcResult}{1+1}直接使用。要将数字四舍五入为整数，您可以int像下面这样使用\pgfmathsetmacro{\calcResult}{int(1+1)}

\documentclass[a4paper,titlepage]{article}

\usepackage{pgf}
\usepackage{siunitx}

\begin{document}

    \pgfmathsetmacro{\calcResult}{int(1+1)}
    \pgfmathprintnumber{\calcResult}

    % Both this line
    \pgfmathparse{\calcResult + 1}
    \pgfmathresult

    % and this one
    \SI{\calcResult}{\cm}

    % do not work.
\end{document}

Answer 2

Harish 的回答是正确的，但另一种方法是使用 LaTeX3 FPU 来完成工作

\documentclass[a4paper,titlepage]{article}

\usepackage{siunitx}
\usepackage{expl3}
\ExplSyntaxOn
  \cs_new_eq:NN \fpeval \fp_eval:n
\ExplSyntaxOff

\begin{document}

\SI{\fpeval{1 + 1}}{\cm}

\SI[round-integer-to-decimal, round-mode = places, round-precision = 1]%
  {\fpeval{1 + 1}}{\cm}

\end{document}