<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div><blockquote type="cite" class=""><div class="">On 12 Sep 2015, at 19:51, Guilherme Andrade <<a href="mailto:g@gandrade.net" class="">g@gandrade.net</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); float: none; display: inline !important;" class="">Partially inspired by jlouis' erl-lenses[1] and an old discussion on this mailing list[2], I've been sketching a library for easier manipulation (both data fetching and updating) of deep data structures</span></div></blockquote><br class=""></div><div>Another library that’s been inspired by erl-lenses (although this has perhaps not been well communicated) is exprecs in parse_trans.</div><div><br class=""></div><div>Example:</div><div><br class=""></div><div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">-module(lens).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">-include_lib("parse_trans/include/exprecs.hrl").</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">-export([t/0]).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">-record(r, {a, b, c}).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">-export_records([r]).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo; min-height: 13px;" class=""><br class=""></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">t() -></div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> R = '#new-r'([{a,1},{b,2},{c,3}]),</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {GetA, SetA} = Lens = '#lens-r'(a),</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> GetA1 = GetA(R),</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> R1 = SetA(17, R),</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> GetA2 = GetA(R1),</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> [{lens, Lens},</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {get_a, GetA1},</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {set_a, 17, R1},</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {get_a, GetA2}].</div><div class=""><br class=""></div></div><div>...</div><div><br class=""></div><div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">Eshell V5.10.4 (abort with ^G)</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">1> c(lens).</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">{ok,lens}</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">2> lens:t().</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class="">[{lens,{#Fun<lens.6.121208397>,#Fun<lens.7.121208397>}},</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {get_a,1},</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {set_a,17,{r,17,2,3}},</div><div style="margin: 0px; font-size: 11px; font-family: Menlo;" class=""> {get_a,17}]</div><div class=""><br class=""></div></div>BR,<div class="">Ulf W</div><div class=""><br class=""><div apple-content-edited="true" class="">
<span class="Apple-style-span" style="border-collapse: separate; border-spacing: 0px;"><div class=""><div class="">Ulf Wiger, Co-founder & Developer Advocate, Feuerlabs Inc.</div><div class=""><a href="http://feuerlabs.com" class="">http://feuerlabs.com</a></div></div><div class=""><br class=""></div></span><br class="Apple-interchange-newline">
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