<html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#FFFFFF" text="#000000"> <div class="moz-cite-prefix">On 2012.07.02. 2:41, Richard O'Keefe wrote: </div> <blockquote cite="mid:DA4C1DE1-B00A-4053-9F2E-69A501BC444A@cs.otago.ac.nz" type="cite"> I find it hard to imagine a parser that would confuse them. Commas can occur in three contexts: f( .... , ... ) where f is an atom immediately adjacent to a left parenthesis; [ ... , ... ] where the comma separates list elements; ... , ... anywhere else. </blockquote> You are right, it is easy to distinguish between them, but not with the rules described on the <a href="http://www.mercury.csse.unimelb.edu.au/information/doc-release/mercury_ref/Terms.html">Terms.html</a> and the <a href="http://www.mercury.csse.unimelb.edu.au/information/doc-release/mercury_ref/Builtin-Operators.html#Builtin-Operators">Builtin-Operators.html</a> disagree with the precedence rules. It was not too hard to make this <a href="https://gist.github.com/3025801/2b48f39914721191f0f3cad9ad2c2520a62bfbf5">change</a>, just I am not sure it will be ok. (The previous versions could not properly parse expressions like ":- pred main(io::di, io::uo) is det.", because of the precedence rules, or maybe I did something wrong during the formulation.) <blockquote cite="mid:DA4C1DE1-B00A-4053-9F2E-69A501BC444A@cs.otago.ac.nz" type="cite"> <blockquote type="cite"> <pre wrap="">- I think the . has also double meaning, but maybe I do misunderstand something: </pre> </blockquote> <pre wrap=""> Yes. A token that is a dot followed by white space is an end of term token; other dots are not.</pre> </blockquote> Thanks, this was not clear from the reference. <blockquote cite="mid:DA4C1DE1-B00A-4053-9F2E-69A501BC444A@cs.otago.ac.nz" type="cite"> <pre wrap=""> Tokens may be made of sequences of symbols like ++, +*@, and even .. and ./* are possible tokens. However, such a sequence may not include %, so we'd expect "x.% foo!" to be a well terminated clause as it is in Prolog.</pre> </blockquote> Interesting, so ./* is a possible operator, but .% is not? That's good to know. <blockquote cite="mid:DA4C1DE1-B00A-4053-9F2E-69A501BC444A@cs.otago.ac.nz" type="cite"> <pre wrap="">Like Prolog, Mercury allows user-defined operators, so it is not clear to me how you can build an LL(1) parser unless it can process those declarations.</pre> </blockquote> Yeah, I did know about this from Prolog, but I thought in Mercury these are more limited, ex. they can have only precedence 120, they should be between backquotes ("<span style="color: rgb(0, 0, 0); font-family: 'Times New Roman'; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; display: inline !important; float: none; ">a name, a module qualified name (see <a href="http://www.mercury.csse.unimelb.edu.au/information/doc-release/mercury_ref/The-module-system.html#The-module-system" style="font-family: 'Times New Roman'; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; ">The module system</a><span style="color: rgb(0, 0, 0); font-family: 'Times New Roman'; font-size: medium; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; display: inline !important; float: none; ">), or a variable between grave accents (backquotes)"). Could you please provide a link to this definition? Thanks, gabor PS.: I still have problems with the precedence 950 fxy parts, because of the prefix and infix + (-?) operators. </body> </html>