samcarter
> This is part of the Summer of Code 2022 series, see https://topanswers.xyz/tex?q=2059 for more information
Today's puzzle is a fun one: calculate pi
Top Answer
samcarter
*no spoiler*
Today, I wanted to learn about random numbers in expl3, so I decided to go for a Monte Carlo approach to approximate pi:
```
\documentclass{article}
\begin{document}
Today’s puzzle is a fun one: calculate pi
\ExplSyntaxOn
\int_new:N \l_sam_a_int
\int_new:N \l_sam_b_int
\int_new:N \l_sam_count_int
\int_zero:N \l_sam_count_int
\int_new:N \l_sam_rep_int
\int_set:Nn \l_sam_rep_int { 1000000 }
\int_step_inline:nn {\l_sam_rep_int}
{
\int_set:Nn \l_sam_a_int { \int_rand:n {10000} }
\int_set:Nn \l_sam_b_int { \int_rand:n {10000} }
\int_compare:nNnT { \l_sam_a_int * \l_sam_a_int + \l_sam_b_int * \l_sam_b_int } < { 10000 * 10000 } { \int_incr:N \l_sam_count_int }
}
\par \fp_eval:n { \l_sam_count_int * 4.0 / \l_sam_rep_int }
\ExplSyntaxOff
\end{document}
```