Modifying argument in macro

Question

I need to modify an argument of macro.
For example #4 equals to 1.1 Optimal solution of RNASP

When I write Figure #4, output is this:
Figure 1.1 Optimal solution of RNASP

But I need this:
Figure 1.1: Optimal solution of RNASP

I suppose I need some text operations like:

• Split text to two. Figure number and text.
• Add "Figure" word to start and ":" to end of the first part
• Make first part bold
• Combine first and second part and set as new variable to use in macro

Macro:

\def\@mymacro#1#2#3#4#5{
  ...
  \vskip 2cm
  Figure #4
  ...
}

Edit: I figured out that, for example in one instance #4 equals to the following string. I obtained it by making \detokenize{#4}

\hyper@linkstart {link}{\Hy@tocdestname }{\numberline {1.1}{\ignorespaces Optimal solution of RNASP.\relax }}\hyper@-linkend

When I make detokenize these functions work:

\StrLen{\detokenize{#4}}

\StrLeft{\detokenize{#4}}{30}

But this doesn't work:

\StrBetween{\detokenize{#4}}{foo}{bar}

Besides I need to put a : just after the figure number and make bold before the start of the caption.

Edit: Although having other class functions and definitions, I removed my other content and created an overleaf project. String manipulation can be seen on 206-208 of the gsu12.def file. https://www.overleaf.com/16674170vmvhjncqjndv

I get this error:
https://ibb.co/gZUn2d

Answer 1

If you are using this to adjust figure captions, I would go with @Mico's suggestion and make use of the caption package. But, as an exercise on how to do this, one way is to use the xstring package and extract the string before and after the first space:

Code

\documentclass{article}
\usepackage{xstring}

\def\mymacro#1#2#3#4#5{%
    \StrBefore{#4}{ }[\FigNum]%
    \StrBehind{#4}{ }[\FigLabel]%
    \textbf{Figure \FigNum}:~\FigLabel%
}%

\begin{document}

\mymacro{}{}{}{1.1 Optimal solution of RNASP}{}

\end{document}