{"id":322,"date":"2015-03-25T20:03:52","date_gmt":"2015-03-26T01:03:52","guid":{"rendered":"http:\/\/huewhite.com\/umb\/?p=322"},"modified":"2015-03-25T23:40:13","modified_gmt":"2015-03-26T04:40:13","slug":"current-project","status":"publish","type":"post","link":"https:\/\/huewhite.com\/umb\/2015\/03\/25\/current-project\/","title":{"rendered":"Current Project"},"content":{"rendered":"

My current free time project is the implementation of an XML SAX-like parser (much like that offered by Apache<\/a>), but written in (and for) Mythryl, a functional language heavily derived from SML\/NJ; the goal of the folks working on Mythryl<\/a> is to transform SML\/NJ from an academic language mainly used for doing PhD work into a production level language usable by commercial entities.\u00a0 I’m doing this for these reasons:<\/p>\n

    \n
  1. Mythryl doesn’t have such an XML parser;<\/li>\n
  2. I’m doing it using a recursive descent parser<\/a> engine;<\/li>\n
  3. And I’m doing it using the EBNF definition of XML<\/li>\n<\/ol>\n

    The latter two reasons can be best illustrated from an example.\u00a0 From the definition of XML<\/a> comes this specification:<\/p>\n

    prolog ::= XMLDecl? Misc* (doctypedecl Misc*)?<\/p><\/blockquote>\n

    The ‘?’ means optional, and the ‘*’ means the element may appear 0 or more times.\u00a0 This is an ordered set of instructions, as in “first this and then this and then this ….” other statements can also include “or” statements.\u00a0 The words themselves refer to other specifications; eventually, those specifications will actually mention characters in specific formats.<\/p>\n

    In Mythryl I can write, given sufficient preparation,<\/p>\n

    prolog = |xml_decl| & <misc> & |(doctypedecl & <misc> )| ;<\/p><\/blockquote>\n

    Here, the |xyz| means xyz is optional, the <xyz> means xyz may apply 0 or more times, and the ‘a & b’ means ‘a and then b’, as discussed above – i.e, the ordering mechanism. \u00a0 Given a little leeway for capitalization conventions and symbol changes, and the Mythryl code assumes an amazing resemblance to the EBNF – which means I can copy the EBNF from the document, make a couple of changes, and all of a sudden I have a parser to handle the syntax; a little more meddling and I have semantic support.\u00a0 And the semantic can be added as I have time; the parsing works on any valid XML doc, and I can slowly add in the other details, such as detecting problems with well-formedness, etc.<\/p>\n

    I’m interested in just how close I can come to using the EBNF, how quickly I can go from copying to full-blown functionality, and the post-development maintenance aspects – if any, of course.\u00a0 One of the interesting facets of using Mythryl is that about half the time, once you get it to compile something (and that can be a challenge, even for an experienced programmer, for someone new to Mythryl), it Just Works – a phrase that the developer of Mythryl has been using.\u00a0 No further debug …<\/p>\n

    That hasn’t applied to the parsing engine, as shoving large amounts of data at it had a performance impact; I may have gotten around that with an optimization; generally, though, functional programmers are encouraged to design a good solution without worrying about performance – let the compiler do it.\u00a0 One estimate of its garbage collection is that it’s 10 times faster than Java.<\/p>\n

    As a quick PS, this<\/del> the recursive descent parser isn’t built into Mythryl; it’s a part of a small library I developed using a Mythryl tutorial<\/a> as a starting point.\u00a0 Operator overloads and currying are very interesting after decades of programming in C and some OO languages.<\/p>\n

     <\/p>\n","protected":false},"excerpt":{"rendered":"

    My current free time project is the implementation of an XML SAX-like parser (much like that offered by Apache), but written in (and for) Mythryl, a functional language heavily derived from SML\/NJ; the goal of the folks working on Mythryl is to transform SML\/NJ from an academic language mainly used \u2026 Continue reading → <\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1],"tags":[],"class_list":["post-322","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/posts\/322","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/comments?post=322"}],"version-history":[{"count":2,"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/posts\/322\/revisions"}],"predecessor-version":[{"id":331,"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/posts\/322\/revisions\/331"}],"wp:attachment":[{"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/media?parent=322"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/categories?post=322"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/huewhite.com\/umb\/wp-json\/wp\/v2\/tags?post=322"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}