<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style> </head> <body dir="ltr"> <div><span class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)">Thank you everyone -- that has been very helpful.</span><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0"> I admit that I was using an older version of Mercury (20.06.1). On that version, I *was* able to use either `=` or `is` for the mathematical equations. I have now installed the latest release.</span></span></div> <div class="elementToProof"><span class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0"><br> </span></span></div> <div class="elementToProof"><span class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0"> I admit that I was using an older version of Mercury (20.06.1). On that version, I *was* able to use either `=` or `is` for the mathematical equations. I have now installed the latest release.</span></span></div> <div><span class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0"></span></span></div> <div class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0"><br> </span></div> <div class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0">Julien: that was the answer that I was hoping for:).</span></div> <div class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0"><br> </span></div> <div class="elementToProof FluidPluginCopy"><span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="ContentPasted0 ContentPasted1 ContentPasted2">Tomas: your code is elegant. I understand that lists or arrays would be quite suitable for the given example -- but my motivating case is for doing bag aggregates on (nondet) relationships (see <a href="https://rosettacode.org/wiki/Merge_and_aggregate_datasets#Mercury">https://rosettacode.org/wiki/Merge_and_aggregate_datasets#Mercury</a>). <br> </span></div> <div class="_Entity _EType_OWALinkPreview _EId_OWALinkPreview _EReadonly_1"> <div class="LPBorder437744" style="margin-top:16px;margin-bottom:16px;max-width:800px;min-width:424px"> <table style="padding:12px 36px 12px 12px;width:100%;border-width:1px;border-style:solid;border-color:rgb(200, 200, 200);border-radius:2px"> <tbody> <tr style="border-spacing:0px" valign="top"> <td> <div style="margin-right:12px;height:160px;overflow:hidden"><a target="_blank" href="https://rosettacode.org/wiki/Merge_and_aggregate_datasets#Mercury"><img alt="" style="display:block" width="112" height="160" src="https://static.miraheze.org/rosettacodewiki/d/d3/RosettaCodeTitle.png"></a></div> </td> <td style="width:100%"> <div style="font-size:21px;font-weight:300;margin-right:8px;font-family:"wf_segoe-ui_light", "Segoe UI Light", "Segoe WP Light", "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif;margin-bottom:12px"> <a target="_blank" href="https://rosettacode.org/wiki/Merge_and_aggregate_datasets#Mercury" data-loopstyle="link">Merge and aggregate datasets - Rosetta Code</a></div> <div style="font-size:14px;max-height:100px;color:rgb(102, 102, 102);font-family:"wf_segoe-ui_normal", "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif;margin-bottom:12px;margin-right:8px;overflow:hidden"> Merge and aggregate datasets Task. Merge and aggregate two datasets as provided in .csv files into a new resulting dataset. Use the appropriate methods and data structures depending on the programming language.</div> <div style="font-size:14px;color:rgb(166, 166, 166);font-family:"wf_segoe-ui_normal", "Segoe UI", "Segoe WP", Tahoma, Arial, sans-serif"> rosettacode.org</div> </td> </tr> </tbody> </table> <div class="uHkAz" tabindex="0" title="Remove link preview"><i data-icon-name="Cancel" class="Rm9Q1 root-189"></i></div> </div> </div> <div style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="elementToProof FluidPluginCopy"> <span style="background-color:rgb(255, 255, 255)" class="ContentPasted0 ContentPasted1 ContentPasted2 FluidPluginCopy ContentPasted3">With the recent interest in Verse (<a href="https://news.ycombinator.com/item?id=33946933" class="ContentPasted3">https://news.ycombinator.com/item?id=33946933</a>), which combines nondeterminism and functional aspects, I hope there will be increased interest in Mercury. </span></div> <div style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="elementToProof FluidPluginCopy"> <br> </div> <span style="font-family:Calibri, Arial, Helvetica, sans-serif;font-size:12pt;color:rgb(0, 0, 0);background-color:rgb(255, 255, 255)" class="elementToProof FluidPluginCopy">Sincerely, Mark.</span> <div class="elementToProof" style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"> <span style="font-family: Calibri, Arial, Helvetica, sans-serif; font-size: 12pt; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"><br> </span></div> <div id="appendonsend"></div> <hr style="display:inline-block;width:98%" tabindex="-1"> <div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> Tomas By <tomas@basun.net><br> <b>Sent:</b> 22 December 2022 16:13<br> <b>To:</b> Mark Clements <mark.clements@ki.se><br> <b>Cc:</b> users@lists.mercurylang.org <users@lists.mercurylang.org><br> <b>Subject:</b> Re: [m-users.] Returning a predicate from a function</font> <div> </div> </div> <div class="BodyFragment"><font size="2"><span style="font-size:11pt;"> <div class="PlainText">[You don't often get email from tomas@basun.net. Learn why this is important at <a href="https://aka.ms/LearnAboutSenderIdentification">https://aka.ms/LearnAboutSenderIdentification</a> ]<br> <br> On Thu, 22 Dec 2022 12:52:52 +0100, Mark Clements wrote:<br> > main(!IO) :-<br> > test1(!IO), % OK<br> > test2(!IO). % Does not compile<br> ><br> > :- pred test1(io::di, io::uo) is det.<br> > test1(!IO) :-<br> > Data = (pred(Y::out) is nondet :- nondet_member(I,range(1,5)), Y = float(I)), % some data<br> > LnData = (pred(Y::out) is nondet :- Data(X), Y = math.ln(X)), % a transformation<br> > aggregate(LnData, print_line, !IO).<br> ><br> > :- pred test2(io::di, io::uo) is det.<br> > test2(!IO) :-<br> > Data = (pred(Y::out) is nondet :- nondet_member(I,range(1,5)), Y = float(I)), % some data<br> > LnData = f_ln(Data), %% This transformation does not compile:(<br> > aggregate(LnData, print_line, !IO).<br> ><br> > :- func f_ln(pred(float)::(pred(out) is nondet)) = (pred(float)::(pred(out) is nondet)).<br> > f_ln(Pred) = (pred(Y::out) is nondet :- Pred(X), Y is math.ln(X)).<br> <br> <br> I'm not 100% sure what you mean for this to do. In particular I am not<br> sure what "aggregate" does (in Python I assume).<br> <br> Some general points: maths is not nondet; the basic data structure is<br> a list. not some abstract generator as in some other languages that I<br> could mention; you do not always need all these declarations.<br> <br> This seems to work:<br> <br> <br> |:- module test.<br> |<br> |:- interface.<br> |:- import_module io.<br> |:- pred main(io::di, io::uo) is det.<br> |<br> |:- implementation.<br> |:- import_module int, float, list.<br> |:- use_module math.<br> |<br> |main(!IO) :-<br> | test1(!IO),<br> | test2(!IO).<br> |<br> |:- pred test1(io::di, io::uo) is det.<br> |<br> |test1(!IO) :-<br> | Data = map(float,1..5),<br> | LnData = map(math.ln,Data),<br> | write_list(LnData,"",print_line,!IO).<br> |<br> |:- pred test2(io::di, io::uo) is det.<br> |<br> |test2(!IO) :-<br> | Data = map(float,1..5),<br> | LnData = map(f_ln,Data),<br> | write_list(LnData,"",print_line,!IO).<br> |<br> |:- func f_ln(float::in) = (float::out) is det.<br> |<br> |f_ln(F0) = F :- F = math.ln(F0).<br> |<br> |:- end_module test.<br> <br> <br> Is this what you meant?<br> <br> /Tomas<br> </div> </span></font></div> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <meta http-equiv="Content-Style-Type" content="text/css"> <title></title> <meta name="Generator" content="Cocoa HTML Writer"> <meta name="CocoaVersion" content="1561.6"> <style type="text/css"> p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 14.0px; font: 12.0px Times; color: #000000; -webkit-text-stroke: #000000; min-height: 14.0px} p.p2 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 14.0px; font: 12.0px Times; color: #000000; -webkit-text-stroke: #000000} span.s1 {font-kerning: none} span.s2 {text-decoration: underline ; font-kerning: none; color: #0000ee; -webkit-text-stroke: 0px #0000ee} </style> <p class="p1"><span class="s1"></span><br> </p> <p class="p1"><span class="s1"></span><br> </p> <p class="p2"><span class="s1"><i>När du skickar e-post till Karolinska Institutet (KI) innebär detta att KI kommer att behandla dina personuppgifter. </i><a href="https://ki.se/medarbetare/integritetsskyddspolicy"><span class="s2">Här finns information om hur KI behandlar personuppgifter</span></a>.<span class="Apple-converted-space"> </span></span></p> <p class="p1"><span class="s1"></span><br> </p> <p class="p2"><span class="s1"><i>Sending email to Karolinska Institutet (KI) will result in KI processing your personal data.</i> <a href="https://ki.se/en/staff/data-protection-policy"><span class="s2">You can read more about KI’s processing of personal data here</span></a>.<span class="Apple-converted-space"> </span></span></p> </body> </html>