<html><head></head><body>Hi,<br><br>What you are describing can be done with "lenses". They're a functional construct to get/update data from nested data structures. <br><br>While googling I found an older discussion on this mailiing list <a href="http://erlang.org/pipermail/erlang-questions/2015-September/086068.html.">http://erlang.org/pipermail/erlang-questions/2015-September/086068.html.</a><br><br>Hope that helps.<br><br> - Christophe<br><br><div class="gmail_quote">On 16 June 2021 04:04:38 CEST, "瀬川昂弘" <123430024@ccalumni.meijo-u.ac.jp> wrote:<blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div dir="ltr"><div dir="ltr"><div dir="ltr"><div>Assuming,</div><div>Map = <span style="color:rgb(0,0,0);font-family:Menlo;font-size:11px">#{a => b,c => #{1 => 2,3 => 4,5 => #{x => y}}}.</span></div><div><br></div><div><font color="#000000" face="Menlo"><span style="font-size:11px">Expected:</span></font></div><div><font color="#000000" face="Menlo"><span style="font-size:11px">maps:new_find_fun(Key = 5, Map) = {ok,</span></font><span style="color:rgb(0,0,0);font-family:Menlo;font-size:11px">#{x => y}</span><span style="font-size:11px;color:rgb(0,0,0);font-family:Menlo">}.</span><br></div><div><br></div><div><font color="#000000" face="Menlo"><span style="font-size:11px">It's useful there is the above feature, in my guess.</span></font></div><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr">Takahiro Segawa.<br>E-mail：<span><a href="mailto:123430024@ccalumni.meijo-u.ac.jp" target="_blank">123430024@ccalumni.meijo-u.ac.jp</a></span><br></div></div></div></div></div>
</blockquote></div><br>-- <br>Sent from my Android device with K-9 Mail. Please excuse my brevity.</body></html>