Optimize delimiter by assigning it to the character?

[user202729]

There are 2 different ways used by the code to define math control sequences:

• for mathord etc.: \let \uparrow ↑

  https://github.com/wspr/unicode-math/blob/master/um-code-setchar.dtx#L56

• for mathopen etc.:. \protected\def \langle {\Udelimiter 4\symoperators "027E8\scan_stop: }

  https://github.com/wspr/unicode-math/blob/master/um-code-setchar.dtx#L203

It appears that the first approach is always better and works for both? Did I miss something?

Some tests. The first one is faster as well.

%! TEX program = lualatex
\documentclass{article}
\usepackage{unicode-math}
\usepackage{l3benchmark}
\begin{document}

\meaning\langle  % \Udelimiter 4 \symoperators "027E8 \scan_stop:

mathcode: "\csname int_to_Hex:n\endcsname{\Umathcodenum `⟨}

delcode: "\csname int_to_Hex:n\endcsname{\Udelcodenum `⟨}

\[\langle 123\]

\ExplSyntaxOn
\benchmark:n{\setbox0 \vbox{\[\langle 123\]}}
\fp_use:N \g_benchmark_time_fp
\ExplSyntaxOff

\[\left\langle \frac{123}{456} \right.\]

\[\bigg\langle 123\]

\[\biggl\langle 123\]

\ExplSyntaxOn
\benchmark:n{\setbox0 \vbox{\[\left\langle \frac{123}{456} \right.\]}}
\fp_use:N \g_benchmark_time_fp
\ExplSyntaxOff

\let \oldlangle \langle
\let \langle ⟨

\[\langle 123\]

\ExplSyntaxOn
\benchmark:n{\setbox0 \vbox{\[\langle 123\]}}
\fp_use:N \g_benchmark_time_fp
\ExplSyntaxOff

\[\left\langle \frac{123}{456} \right.\]

\[\bigg\langle 123\]

\[\biggl\langle 123\]

\ExplSyntaxOn
\benchmark:n{\setbox0 \vbox{\[\left\langle \frac{123}{456} \right.\]}}
\fp_use:N \g_benchmark_time_fp
\ExplSyntaxOff

\let \langle \oldlangle

\ExplSyntaxOn
\benchmark:n{\setbox0 \vbox{\[\langle 123\]}}
\fp_use:N \g_benchmark_time_fp
\ExplSyntaxOff

\ExplSyntaxOn
\benchmark:n{\setbox0 \vbox{\[\left\langle \frac{123}{456} \right.\]}}
\fp_use:N \g_benchmark_time_fp
\ExplSyntaxOff

\end{document}