|
|
| Author |
Message |
< Erlang ~ Late night question on records and types... |
| seancharles |
 Posted: Tue Aug 07, 2007 10:09 pm |
 |
|
|
User
Joined: 18 Jul 2007
Posts: 57
|
Given the record:
Code: -record( menuitem,
{
label, % Printable string label
id, % numerical identifier
page, % the /pages/<page>.yaws display page
title=null % Browser title string, null = default
}).
and a population of:
Code:
#menuitem { label="Home",
id=1,
page=home},
How do I get the 'id' to be a number, currently my lookup code fails because it has a number and an atom ?
What did I do wrong ?
 |
|
|
| Back to top |
 
|
| Jan Henry Nystrom |
| Posted: Wed Aug 08, 2007 2:23 am |
|
|
|
User
Joined: 09 Oct 2006
Posts: 28
Location: Uppsala, Sweden
|
seancharles wrote: Given the record:
Code: -record( menuitem,
{
label, % Printable string label
id, % numerical identifier
page, % the /pages/<page>.yaws display page
title=null % Browser title string, null = default
}).
and a population of:
Code:
#menuitem { label="Home",
id=1,
page=home},
How do I get the 'id' to be a number, currently my lookup code fails because it has a number and an atom ?
What did I do wrong ?
I am not entirely sure what the question is, so I will state what I think it is and then answer that question. Are you asking how to get the position of the id field in the tuple representing the record? In that case you can write #menuitem.id which will evaluate to 3. If you are trying to lookup a member in a list for example, one would write
Code: listst:keysearch(4711, #menuitem.id, List)
to retrieve the record with id 4711 from a list of menuitem records.
/Cheers Henry |
_________________
Jan Henry Nystrom
Training & Research Manager @ Erlang Training and Consulting Ltd
http://www.erlang-consulting.com |
|
| Back to top |
   
|
| Mazen |
| Posted: Wed Aug 08, 2007 8:27 am |
|
|
|
User
Joined: 20 Jul 2006
Posts: 164
Location: London
|
Quote: currently my lookup code fails because it has a number and an atom
Not quite sure what you mean here... care to elaborate for us?  |
|
|
| Back to top |
|
| seancharles |
| Posted: Fri Aug 10, 2007 11:07 am |
|
|
|
User
Joined: 18 Jul 2007
Posts: 57
|
Sorry about the delay, been offline for a few days.
Anyway, I have read all your comments and learnt a few tricks so far!
Read my lips: N - O - O - B - I - E
That's me! 42 this year and still a newbie! Never too old to be a newbie eh! LOL The mistake, again, was mine, god I love/hate Erlang. HA HA HA... in a nutshell, I was was actually calling list_to_atom() in a higher up call and didn't see it for the trees!
I am writing a commercial web application as a personal project. Erlang has so many advantages that I can't begin to count them! I think in a few months time I will be ready to host, test and then launch my service, I think it will be a pretty unique thing when its finished, if only my lameness at reading the documentation would stop holding me up.
Pattern matching for example, every time I read the docs I learn something new, the best examples I have so far are YAWS source code (I'm using it to run my service after reading a yaws/apache shoot-out) and it blows me away.
Pattern matching rocks, then there are guard expressions and case statements. Man, I didn't think it could get Better than Smalltalk, then I read Alan Kays' quote about LISP, then I thought LISP was the dogs and after struggling with SBCL and getting to like it I got a bit pissed at not having a 'stable and portable' (no flame war intended) environment that had *everything in it* out of the box.
Erlang has that.
Better stop here, I could talk all day about how much Erlang has my interest.
Thanks for all your help guys,
Sean Charles. |
|
|
| Back to top |
|
|
|
All times are GMT
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You cannot download files in this forum
|
|
|
Digg It
Del.icio.us
Reddit
Facebook
Stumble Upon
Technorati
