LaTeX listings包：如何按位置而非分隔符定义注释？

Got it, let's tackle this problem with the listings package and GAMS code formatting. Here's a practical solution to get those post-declaration descriptions recognized as comments, with proper styling and no accidental keyword highlighting:

Step 1: Define the Custom GAMS Language in Your Preamble #

First, add this to your LaTeX preamble to set up the GAMS language definition, including handling both line comments (!) and the double-quoted description text:

\usepackage{listings}
\usepackage{xcolor}

% Define custom colors for GAMS elements
\definecolor{gamsKeyword}{RGB}{0, 51, 102}   % Dark blue for keywords
\definecolor{gamsComment}{RGB}{102, 102, 102} % Gray for comments/descriptions
\definecolor{gamsBackground}{RGB}{248, 248, 248} % Light gray background (optional)

% Custom GAMS language definition
\lstdefinelanguage{GAMS}{
    % Core GAMS keywords (add more as needed)
    keywords={Variable, Variables, Equation, Equations, Model, Solve, Display,
              Set, Sets, Parameter, Parameters, Scalar, Scalars, Positive},
    keywordstyle=\color{gamsKeyword}\bfseries,
    % Handle standard GAMS line comments (starts with !)
    comment=[l]{!},
    commentstyle=\color{gamsComment}\itshape,
    % Treat double-quoted descriptions as comment-style blocks
    moredelim=[s]["][\color{gamsComment}\itshape],
    % Optional: Make keyword matching case-insensitive (adjust if needed)
    sensitive=false,
    % Optional formatting tweaks
    basicstyle=\ttfamily\small,
    backgroundcolor=\color{gamsBackground},
    numbers=left,
    numberstyle=\tiny\color{gamsComment},
    frame=single,
    breaklines=true
}

Step 2: Use the Custom Language in Your Document #

Now you can insert GAMS code blocks with proper formatting, where both line comments and post-declaration descriptions are styled as comments, and keywords don't get highlighted inside descriptions:

\begin{lstlisting}[language=GAMS]
Set i "Set of production plants" /PlantA, PlantB, PlantC/;
Parameter capacity(i) "Maximum output per plant" /PlantA 500, PlantB 750, PlantC 600/;
Variable x(i) "Units produced at each plant" /PlantA.L 200/;
Positive Variable y(i) "Positive production only";

Equation obj "Minimize total production cost";
obj.. sum(i, 1.2*capacity(i)*x(i)) =E= 15000;

Model production_plan "Optimal production model" /all/;
Solve production_plan using LP minimizing obj;

Display x.l, y.m;
! This is a standard line comment
\end{lstlisting}

How It Works #

• Keyword Highlighting: We define core GAMS keywords and apply a bold dark blue style to them.
• Line Comments: The standard GAMS line comment (!) is handled with comment=[l]{!}, applying the gray italic comment style.
• Description Text: The moredelim=[s]["][\color{gamsComment}\itshape] line tells listings to treat any text wrapped in double quotes as a special block, applying the same comment style as line comments. This ensures:
  1. The description text gets your desired comment color/style.
  2. Any text inside the quotes (even if it matches a keyword) won't be highlighted as a keyword.

Optional Tweaks #

• If you need to handle double quotes in other contexts (rare in standard GAMS), you can refine the moredelim rule with regex-based matching (note: listings regex support is limited, but you can use moredelim=[il][regex] for inline matching if needed).
• Adjust the colors, font sizes, or frame styles to match your document's design.

内容的提问来源于stack exchange，提问作者Niclas von Caprivi