Comments on: Erlang Makes My Head Hurt http://davetroy.com/posts/erlang-makes-my-head-hurt Design, Entrepreneurship, Economics and Software Tue, 08 May 2012 16:58:00 +0000 hourly 1 http://wordpress.org/?v=3.3.2 By: Dave Troy http://davetroy.com/posts/erlang-makes-my-head-hurt#comment-522 Dave Troy Sat, 24 Oct 2009 18:25:23 +0000 http://dave.popvox.com/?p=8#comment-522 Ah, OK! Thanks for the help. It felt to me that it was this sort of a problem, but I wasn't sure how to proceed given my unfamiliarity with the language.<br></br><br>I will now press ahead! Best, Dave</br> Ah, OK! Thanks for the help. It felt to me that it was this sort of a problem, but I wasn't sure how to proceed given my unfamiliarity with the language.

I will now press ahead! Best, Dave

]]> By: Dave Troy http://davetroy.com/posts/erlang-makes-my-head-hurt#comment-9 Dave Troy Fri, 09 Nov 2007 20:32:00 +0000 http://dave.popvox.com/?p=8#comment-9 Ah, OK! Thanks for the help. It felt to me that it was this sort of a problem, but I wasn't sure how to proceed given my unfamiliarity with the language.<br/><br/>I will now press ahead! Best, Dave Ah, OK! Thanks for the help. It felt to me that it was this sort of a problem, but I wasn’t sure how to proceed given my unfamiliarity with the language.

I will now press ahead! Best, Dave

]]> By: Ulf Wiger http://davetroy.com/posts/erlang-makes-my-head-hurt#comment-8 Ulf Wiger Tue, 06 Nov 2007 13:45:00 +0000 http://dave.popvox.com/?p=8#comment-8 Dave,<br/><br/>You've stumbled upon one of the syntactic quirks of Erlang. For historical reasons, a record is syntactic sugar for a "tagged tuple". What you see in the shell is the tuple representation of a record.<br/><br/>Since you've included "xmerl.hrl" in your module, you should be able to use record syntax when matching. If you try the code in the shell, you need to make the shell aware of the record definition:<br/><br/>9> <b>xmerl_xpath:string("//id/text()", XML).</b><br/>[{xmlText,[{id,1},{entry,1}],<br/> 1,<br/> [],<br/> "http://gdata.youtube.com/feeds/users/uwiger",<br/> text}]<br/>10> <b>code:which(xmerl).</b><br/>"/usr/local/lib/erlang/lib/xmerl-1.1.2/ebin/xmerl.beam"<br/>11> <b>rr("/usr/local/lib/erlang/lib/xmerl-1.1.2/include/xmerl.hrl").</b><br/>[xmerl_event,<br/>...,<br/> xmlText]<br/>12> <b>[#xmlText{value = Id}] = xmerl_xpath:string("//id/text()", XML).</b><br/>[#xmlText{parents = [{id,1},{entry,1}],<br/> pos = 1,<br/> language = [],<br/> value = "http://gdata.youtube.com/feeds/users/uwiger",<br/> type = text}]<br/>13> <b>Id.</b><br/>"http://gdata.youtube.com/feeds/users/uwiger" Dave,

You’ve stumbled upon one of the syntactic quirks of Erlang. For historical reasons, a record is syntactic sugar for a “tagged tuple”. What you see in the shell is the tuple representation of a record.

Since you’ve included “xmerl.hrl” in your module, you should be able to use record syntax when matching. If you try the code in the shell, you need to make the shell aware of the record definition:

9> xmerl_xpath:string(“//id/text()”, XML).
[{xmlText,[{id,1},{entry,1}],
1,
[],
“http://gdata.youtube.com/feeds/users/uwiger”,
text}]
10> code:which(xmerl).
“/usr/local/lib/erlang/lib/xmerl-1.1.2/ebin/xmerl.beam”
11> rr(“/usr/local/lib/erlang/lib/xmerl-1.1.2/include/xmerl.hrl”).
[xmerl_event,
...,
xmlText]
12> [#xmlText{value = Id}] = xmerl_xpath:string(“//id/text()”, XML).
[#xmlText{parents = [{id,1},{entry,1}],
pos = 1,
language = [],
value = “http://gdata.youtube.com/feeds/users/uwiger”,
type = text}]
13> Id.
“http://gdata.youtube.com/feeds/users/uwiger”

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