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  • SQL to retrieve the latest records, grouping by unique foreign keys

    - by jbox
    I'm creating query to retrieve the latest posts in a forum using a SQL DB. I've got a table called "Post". Each post has a foreign key relation to a "Thread" and a "User" as well as a creation date. The trick is I don't want to show two posts by the same user or two posts in the same thread. Is it possible to create a query that contains all this logic? # Grab the last 10 posts. SELECT id, user_id, thread_id FROM posts ORDER BY created_at DESC LIMIT 10; # Grab the last 10 posts, max one post per user SELECT id, user_id, thread_id FROM post GROUP BY user_id ORDER BY date DESC LIMIT 10; # Grab the last 10 posts, max one post per user, max one post per thread???

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  • Django equivalent for latest entry for each user

    - by paul-ogrady
    Hi, I'm surprised this question hasn't come up. Couldn't find much on the web. Using Entry.objects.latest('created_at') I can recover the latest entry for all Entry objects, but say if I want the latest entry for each user? This is something similar to an SQL latest record query. But how do I achieve this using the ORM? Here is my approach I'm wondering if it is the most efficient way to do what I want. First I perform a sub query: Objects are grouped by user and the Max (latest) created_by field is returned for each user (created_at__max) I then filter Entry objects based on the results in the subquery and get the required objects. Entry.objects.filter(created_at__in=Entry.objects.values('user').annotate(Max('created_at')).values_list('created_at__max')) or using a manager: class UsersLatest(models.Manager): def get_query_set(self): return Super(UsersLatest,self).get_query_set().filter(created_at__in=self.model.objects.values('user').annotate(Max('created_at')).values_list('created_at__max')) Is there a more efficient way? possibly without sub query? Thanks, Paul

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  • Representing robot's elbow angle in 3-D

    - by Onkar Deshpande
    I am given coordinates of two points in 3-D viz. shoulder point and object point(to which I am supposed to reach). I am also given the length from my shoulder-to-elbow arm and the length of my forearm. I am trying to solve for the unknown position(the position of the joint elbow). I am using cosine rule to find out the elbow angle. Here is my code - #include <stdio.h> #include <math.h> #include <stdlib.h> struct point { double x, y, z; }; struct angles { double clock_wise; double counter_clock_wise; }; double max(double a, double b) { return (a > b) ? a : b; } /* * Check if the combination can make a triangle by considering the fact that sum * of any two sides of a triangle is greater than the remaining side. The * overlapping condition of links is handled separately in main(). */ int valid_triangle(struct point p0, double l0, struct point p1, double l1) { double dist = sqrt(pow((fabs(p1.z - p0.z)), 2) + pow((fabs(p1.y - p0.y)), 2) + pow((fabs(p1.x - p0.x)), 2)); if((max(dist, l0) == dist) && max(dist, l1) == dist) { return (dist < (l0 + l1)); } else if((max(dist, l0) == l0) && (max(l0, l1) == l0)) { return (l0 < (dist + l1)); } else { return (l1 < (dist + l0)); } } /* * Cosine rule is used to find the elbow angle. Positive value indicates a * counter clockwise angle while negative value indicates a clockwise angle. * Since this problem has at max 2 solutions for any given position of P0 and * P1, I am returning a structure of angles which can be used to consider angles * from both direction viz. clockwise-negative and counter-clockwise-positive */ void return_config(struct point p0, double l0, struct point p1, double l1, struct angles *a) { double dist = sqrt(pow((fabs(p1.z - p0.z)), 2) + pow((fabs(p1.y - p0.y)), 2) + pow((fabs(p1.x - p0.x)), 2)); double degrees = (double) acos((l0 * l0 + l1 * l1 - dist * dist) / (2 * l0 * l1)) * (180.0f / 3.1415f); a->clock_wise = -degrees; a->counter_clock_wise = degrees; } int main() { struct point p0, p1; struct angles a; p0.x = 15, p0.y = 4, p0.z = 0; p1.x = 20, p1.y = 4, p1.z = 0; double l0 = 5, l1 = 8; if(valid_triangle(p0, l0, p1, l1)) { printf("Three lengths can make a valid configuration \n"); return_config(p0, l0, p1, l1, &a); printf("Angle of the elbow point (clockwise) = %lf, (counter clockwise) = %lf \n", a.clock_wise, a.counter_clock_wise); } else { double dist = sqrt(pow((fabs(p1.z - p0.z)), 2) + pow((fabs(p1.y - p0.y)), 2) + pow((fabs(p1.x - p0.x)), 2)); if((dist <= (l0 + l1)) && (dist > l0)) { a.clock_wise = -180.0f; a.counter_clock_wise = 180.0f; printf("Angle of the elbow point (clockwise) = %lf, (counter clockwise) = %lf \n", a.clock_wise, a.counter_clock_wise); } else if((dist <= fabs(l0 - l1)) && (dist < l0)){ a.clock_wise = -0.0f; a.counter_clock_wise = 0.0f; printf("Angle of the elbow point (clockwise) = %lf, (counter clockwise) = %lf \n", a.clock_wise, a.counter_clock_wise); } else printf("Given combination cannot make a valid configuration\n"); } return 0; } However, this solution makes sense only in 2-D. Because clockwise and counter-clockwise are meaningless without an axis and direction of rotation. Returning only an angle is technically correct but it leaves a lot of work for the client of this function to use the result in meaningful way. How can I make the changes to get the axis and direction of rotation ? Also, I want to know how many possible solution could be there for this problem. Please let me know your thoughts ! Any help is highly appreciated ...

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  • Using an array in embedded x86 assembly??

    - by Mark V.
    Hey all I have a method (C++) that returns a character and takes an array of characters as its parameters. I'm messing with assembly for the first time and just trying to return the first character of the array in the dl register. Here's what I have so far: char returnFirstChar(char arrayOfLetters[]) { char max; __asm { push eax push ebx push ecx push edx mov dl, 0 mov eax, arrayOfLetters[0] xor edx, edx mov dl, al mov max, dl pop edx pop ecx pop ebx pop eax } return max; } For some reason this method returns a ? Any idea whats going on? Thanks

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  • Random number generation

    - by Chandan Shetty SP
    I am using below code to generate random numbers in range... int randomNumberWithinRange(int min,int max) { int snowSize = 0; do { snowSize = rand()%max; } while( snowSize < min || snowSize > max ); return snowSize; } for(int i = 0; i < 10 ; i++) NSlog("@"%d",\t", randomNumberWithinRange(1,100)); If I quit my application and restart, same set of numbers are generated. How to generate different set of random numbers for every launching.

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  • Why servlet halt a moment in concurrent request.

    - by Hlex
    I use Axis for webservice service. when more than 8 concurrent , there are some request halt randomly for about 30 seconds. I debug by log in every line and found from my code: public class foo{ void bar(){ a(); log.debug('exit from a'); } void a(){ log.debug('exit a'); } the time between "exit a" and "exit from a" are delay about 30 second. This is no reason. I try to increase web container thread pool , heap but didn't help ============== Enviroment websphere 6.1 Spring 2.5 , Hibernate 3 ,Axis 1.6.5 Min heap to 768 Max heap to 1024 Thread pool defult max to 300 Thread pool web container max to 500 ===============

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  • Creating a Large Matrix in ff

    - by Ryan Rosario
    I am trying to create a huge matrix in ff, and I know that ff is good for this sort of thing. But, there is a major problem. The dimensions of the matrix exceed .Machine$max_integer! I am running on a 64 bit machine, using 64bit R and 64bit ff. Is there any way to get around this problem? It's been suggested that R is using the MAXINT value from stdint.h. Is there any way to fix this without changing that file and possibly breaking build? > ffMatrix <- ff(vmode="boolean", dim=c(1e10,1e10)) Error in if (length < 0 || length > .Machine$integer.max) stop("length must be between 1 and .Machine$integer.max") : missing value where TRUE/FALSE needed In addition: Warning message: In ff(vmode = "boolean", dim = c(1e+10, 1e+10)) : NAs introduced by coercion > 1e+10 > .Machine$integer.max [1] TRUE

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  • Grouping with operands question

    - by Filip
    I have a table: mysql> desc kursy_bid; +-----------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-----------+-------------+------+-----+---------+-------+ | datetime | datetime | NO | PRI | NULL | | | currency | varchar(6) | NO | PRI | NULL | | | value | varchar(10) | YES | | NULL | | +-----------+-------------+------+-----+---------+-------+ 3 rows in set (0.01 sec) I would like to select some rows from a table, grouped by some time interval (can be one day) where I will have the first row and the last row of the group, the max(value) and min(value). I tried: select datetime, (select value order by datetime asc limit 1) open, (select value order by datetime desc limit 1) close, max(value), min(value) from kursy_bid_test where datetime > '2009-09-14 00:00:00' and currency = 'eurpln' group by month(datetime), day(datetime), hour(datetime); but the output is: | open | close | datetime | max(value) | min(value) | +--------+--------+---------------------+------------+------------+ | 1.4581 | 1.4581 | 2009-09-14 00:00:05 | 4.1712 | 1.4581 | | 1.4581 | 1.4581 | 2009-09-14 01:00:01 | 1.4581 | 1.4581 | As you see open and close is the same (but they shouldn't be). What should be the query to do what I want?

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  • Convert T-SQL function to PL/SQL

    - by llasarov
    can you help me convert following T-SQL funcntion into Oracle. The function converts a string like service|nvretail;language|de;yyyy|2011; to a table. The main problem I have is the usage of the temp table. I could not find any equivalent to it in Oracle. CREATE FUNCTION [dbo].[TF_ConvertPara] ( @parastringNVARCHAR(max) ) RETURNS @para TABLE ( [Key] varchar(max), [Value] varchar(max) ) begin DECLARE @NextString NVARCHAR(40) DECLARE @Pos1 INT DECLARE @Pos2 INT DECLARE @NextPos INT DECLARE @Delimiter1 NCHAR=';' DECLARE @Delimiter2 NCHAR='|' if substring(@paraString, len(@paraString) - 1, 1) <> @Delimiter1 SET @paraString = @paraString + @Delimiter1 SET @Pos1 = charindex(@Delimiter1, @paraString) WHILE (@pos1 <> 0) BEGIN SET @NextString = substring(@paraString, 1, @Pos1 - 1) SET @paraString = substring(@paraString, @pos1 + 1, len(@paraString)) SET @pos1 = charindex(@Delimiter1, @paraString) SET @Pos2 = charindex(@Delimiter2, @NextString) if (@Pos2 > 0) begin insert into @para values (substring(@NextString, 1, @Pos2 - 1), substring(@NextString, @Pos2 + 1, len(@NextString))) end END return; end Thank you in advance.

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  • How do I transfer this logic into a LINQ statement?

    - by Geoffrey
    I can't get this bit of logic converted into a Linq statement and it is driving me nuts. I have a list of items that have a category and a createdondate field. I want to group by the category and only return items that have the max date for their category. So for example, the list contains items with categories 1 and 2. The first day (1/1) I post two items to both categories 1 and 2. The second day (1/2) I post three items to category 1. The list should return the second day postings to category 1 and the first day postings to category 2. Right now I have it grouping by the category then running through a foreach loop to compare each item in the group with the max date of the group, if the date is less than the max date it removes the item. There's got to be a way to take the loop out, but I haven't figured it out!

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  • MYSQL Convert rows to columns performance problem

    - by Tarski
    I am doing a query that converts rows to columns similar to this post but have encountered a performance problem. Here is the query:- SELECT Info.Customer, Answers.Answer, Answers.AnswerDescription, Details.Code1, Details.Code2, Details.Code3 FROM Info LEFT OUTER JOIN Answers ON Info.AnswerID = Answers.AnswerID LEFT OUTER JOIN (SELECT ReferenceNo, MAX(CASE DetailsIndicator WHEN 'cde1' THEN DetailsCode ELSE NULL END ) Code1, MAX(CASE DetailsIndicator WHEN 'cde2' THEN DetailsCode ELSE NULL END ) Code2, MAX(CASE DetailsIndicator WHEN 'cde3' THEN DetailsCode ELSE NULL END ) Code3 FROM DetailsData GROUP BY ReferenceNo) Details ON Info.ReferenceNo = Details.ReferenceNo There are less than 300 rows returned, but the Details table is about 180 thousand rows. The query takes 45 seconds to run and needs to take only a few seconds. When I type show processlist; into MYSQL it is hanging on "Sending Data". Any thoughts as to what the performance problem might be?

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  • How to avoid timestamp issue in a long query?

    - by pingi
    Hi, I have the following 2 tables: items: id int primary key bla text events: id_items int num int when timestamp without time zone ble text composite primary key: id_items, num and want to select to each item the most recent event (the newest 'when'). I wrote an request, but I don't know if it could be written more efficiently. Also on PostgreSQL there is a issue with comparing Timestamp objects: 2010-05-08T10:00:00.123 == 2010-05-08T10:00:00.321 so I select with 'MAX(num)' Any thoughts how to make it better? Thanks. SELECT i.*, ea.* FROM items AS i JOIN ( SELECT t.s AS t_s, t.c AS t_c, max(e.num) AS o FROM events AS e JOIN ( SELECT DISTINCT id_item AS s, MAX(when) AS c FROM events GROUP BY s ORDER BY c ) AS t ON t.s = e.id_item AND e.when = t.c GROUP BY t.s, t.c ) AS tt ON tt.t_s = i.id JOIN events AS ea ON ea.id_item = tt.t_s AND ea.cas = tt.t_c AND ea.num = tt.o;

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  • reading unformatted fortran file in matlab - which precision?

    - by Griff
    I have just written out a file: real*8 :: vol_cel real*8, dimension(256,256,256) :: dense [... some operations] open(unit=8,file=fname,form="unformatted") write(8)dense(:,:,:)/vol_cell close(8) dense and vol_cell are real*8 variables. My code to read this in in Matlab: fid = fopen(fname,'r'); mesh_raw = fread(fid,256*256*256,'double'); fclose(fid); The min and max values clearly show that it is not reading it in correctly (Min is 0 and max is a largish positive real*8). min = 3.3622e+38 max = -3.3661e+38 What precision do I need to set in Matlab to make it read in the unformatted Fortran file? A somewhat related question: This Matlab code I am using reads binary files OK but not unformatted files. Though I am generating this new data on my Mac OSX using gfortran. It doesn't recognize form="binary" so I can't do it that way. Do I need to add some library?

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  • Oracle aggregate function to return a random value for a group?

    - by tpdi
    The standard SQL aggregate function max() will return the highest value in a group; min() will return the lowest. Is there an aggregate function in Oracle to return a random value from a group? Or some technique to achieve this? E.g., given the table foo: group_id value 1 1 1 5 1 9 2 2 2 4 2 8 The SQL query select group_id, max(value), min(value), some_aggregate_random_func(value) from foo group by group_id; might produce: group_id max(value), min(value), some_aggregate_random_func(value) 1 9 1 1 2 8 2 4 with, obviously, the last column being any random value in that group.

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  • MySQL Query: Winning Auction Bid

    - by mabwi
    I have a small Bidding system that I'm using for a fantasy auction draft. I'm trying to use the below query to pull up the max bids on each player. However, it's not actually giving me the max bid, it's just giving me the first one entered in to the database. SELECT Bid.id FROM bids AS Bid WHERE Bid.active =1 GROUP BY player_id HAVING MAX( Bid.amount ) Here's the Bid table layout, in case it helps: CREATE TABLE IF NOT EXISTS `bids` ( `id` int(10) NOT NULL AUTO_INCREMENT, `user_id` int(10) NOT NULL, `player_id` int(10) NOT NULL, `amount` int(6) NOT NULL, `timestamp` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `winning_bid` int(1) NOT NULL DEFAULT '0', `active` int(1) NOT NULL DEFAULT '1', PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1 ;

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  • Data Access from single table in sql server 2005 is too slow

    - by Muhammad Kashif Nadeem
    Following is the script of table. Accessing data from this table is too slow. SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[Emails]( [id] [int] IDENTITY(1,1) NOT NULL, [datecreated] [datetime] NULL CONSTRAINT [DF_Emails_datecreated] DEFAULT (getdate()), [UID] [nvarchar](250) COLLATE Latin1_General_CI_AS NULL, [From] [nvarchar](100) COLLATE Latin1_General_CI_AS NULL, [To] [nvarchar](100) COLLATE Latin1_General_CI_AS NULL, [Subject] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [Body] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [HTML] [nvarchar](max) COLLATE Latin1_General_CI_AS NULL, [AttachmentCount] [int] NULL, [Dated] [datetime] NULL ) ON [PRIMARY] Following query takes 50 seconds to fetch data. select id, datecreated, UID, [From], [To], Subject, AttachmentCount, Dated from emails If I include Body and Html in select then time is event worse. indexes are on: id unique clustered From Non unique non clustered To Non unique non clustered Tabls has currently 180000+ records. There might be 100,000 records each month so this will become more slow as time will pass. Does splitting data into two table will solve the problem? What other indexes should be there?

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  • Where can I find a jQuery color animation plugin?

    - by George Edison
    I need an up-to-date jQuery color animation plugin that works in IE 8. I tried using the one at http://plugins.jquery.com/project/color but it causes errors like "Invalid property value." in the following line of code from color.js: fx.elem.style[attr] = "rgb(" + [ Math.max(Math.min( parseInt((fx.pos * (fx.end[0] - fx.start[0])) + fx.start[0]), 255), 0), Math.max(Math.min( parseInt((fx.pos * (fx.end[1] - fx.start[1])) + fx.start[1]), 255), 0), Math.max(Math.min( parseInt((fx.pos * (fx.end[2] - fx.start[2])) + fx.start[2]), 255), 0) ].join(",") + ")"; Where can I get something that works? By the way, I really hate IE, if that helps.

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  • How can I debug or set a break statement inside an expression tree?

    - by Abel
    When an external library contains a LINQ provider, and it throws an exception when executing a dynamic expression tree, how can I break when that expression is thrown? For example, I use a third party LINQ2CRM provider, which allows me to call the Max<TSource, TResult>() method of IQueryable, but when it throws an InvalidCastException, I fail to break on the spot when the exception is thrown, making it hard to review the stack-trace because it's already unwinded when the debugger breaks it in my code. I've set "break on throw" for the mentioned exception. My debug settings are: Clarification on where exactly I'd want to break. I do not want to break in side the LINQ Expression, but instead, I want to break when the expression tree is executed, or, put in other words, when the IQueryable extension method Max() calls the override provided by the LINQ provider. The top of the stacktrace looks like this, which is where I would like to break inside (or step through, or whatever): at XrmLinq.QueryProviderBase.Execute[T](Expression expression) at System.Linq.Queryable.Max[TSource,TResult](IQueryable`1 source, Expression`1 selector)

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  • Update options to jQuery slider via form

    - by Coughlin
    I have a jQuery Slider, and I am trying to make it more dynamic by adding three input fields: min max step I want to take those fields and then onblur update my slider options. I read that you can set options like this: $('.selector').slider('option', 'max', 7); And do the same for min,step, etc along with the other options. I tried playing with it yesterday, but I'm not sure how to get it to update. I am using a form with no submit button, so just change on blur. I know I would get the .val() of the input and set it to a variable then would it be: $('.selector').slider('option', 'max', var_here); Any thoughts?

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  • Split a map using Groovy

    - by Tihom
    I want to split up a map into an array of maps. For example, if there is a map with 25 key/value pairs. I want an array of maps with no more than 10 elements in each map. How would I do this in groovy? I have a solution which I am not excited about, is there better groovy version: static def splitMap(m, count){ if (!m) return def keys = m.keySet().toList() def result = [] def num = Math.ceil(m?.size() / count) (1..num).each { def min = (it - 1) * count def max = it * count > keys.size() ? keys.size() - 1 : it * count - 1 result[it - 1] = [:] keys[min..max].each {k -> result[it - 1][k] = m[k] } } result } m is the map. Count is the max number of elements within the map.

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  • POST data disapearing on large file upload

    - by DfKimera
    I'm having issues with a file uploading utility in my PHP application. When sending large files (9MB+) over the form, I get a very odd behaviour: the POST data I've included in the form dissapears, including the file information. I've already increased all PHP limits I could (time limit, max input time, post max size, memory limit and upload max filesize) and I still can't get the proper behaviour. I've tried replacing the regular HTTP forms with a Flash-based solution (SWFUpload, www.swfupload.org), still the same behaviour. I've tried multiple files of similar sizes and its definitely not a particular file issue. I've debugged the POST vars sent using Firebug, and the correct variables are still there in the header, together with the file. What could be going on here?

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  • Any way to optimize this MySQL query?

    - by manyxcxi
    My table looks like this: `MyDB`.`Details` ( `id` bigint(20) NOT NULL, `run_id` int(11) NOT NULL, `element_name` varchar(255) NOT NULL, `value` text, `line_order` int(11) default NULL, `column_order` int(11) default NULL ); I have the following SELECT statement in a stored procedure SELECT RULE ,TITLE ,SUM(IF(t.PASSED='Y',1,0)) AS PASS ,SUM(IF(t.PASSED='N',1,0)) AS FAIL FROM ( SELECT a.line_order ,MAX(CASE WHEN a.element_name = 'PASSED' THEN a.`value` END) AS PASSED ,MAX(CASE WHEN a.element_name = 'RULE' THEN a.`value` END) AS RULE ,MAX(CASE WHEN a.element_name = 'TITLE' THEN a.`value` END) AS TITLE FROM Details a WHERE run_id = runId GROUP BY line_order ) t GROUP BY RULE, TITLE; *runId is an input parameter to the stored procedure. This query takes about 14 seconds to run. The table has 214856 rows, and the particular run_id I am filtering on has 162204 records. It's not on a super high power machine, but I feel like I could be doing this more efficiently. My main goal is to summarize by Rule and Title and show Pass and Fail count columns.

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  • How to correctly and standardly compare floats?

    - by DIMEDROLL
    Every time I start a new project and when I need to compare some float or double variables I write the code like this one: if (fabs(prev.min[i] - cur->min[i]) < 0.000001 && fabs(prev.max[i] - cur->max[i]) < 0.000001) { continue; } Then I want to get rid of these magic variables 0.000001(and 0.00000000001 for double) and fabs, so I write an inline function and some defines: #define FLOAT_TOL 0.000001 So I wonder if there is any standard way of doing this? May be some standard header file? It would be also nice to have float and double limits(min and max values)

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  • How to get array keys in Javascript?

    - by DisgruntledGoat
    I have an array created with this code: var widthRange = new Array(); widthRange[46] = { sel:46, min:0, max:52 }; widthRange[66] = { sel:66, min:52, max:70 }; widthRange[90] = { sel:90, min:70, max:94 }; I want to get each of the values 46, 66, 90 in a loop. I tried for (var key in widthRange) but this gives me a whole bunch of extra properties (I assume they are functions on the object). I can't use a regular for loop since the values are not sequential.

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  • Can't echo jquery (with ajax) variable in php

    - by Lars Kerff
    I'm trying to post a variable through ajax. But it won't echo the variable in php. This are the variables (these are working, seen in the log): $("#slider").bind("valuesChanged", function(e, data){console.log("min: " + data.values.min + " max: " + data.values.max);}); The Ajax part: $("#slider").bind("valuesChanged", function (e, data) { $.ajax({ type: "POST", dataType: "text", url: "../test.php", data: { minValue: data.values.min, maxValue: data.values.max }, async: false, success: function(data){ alert('yeah') }, error: function(xhr) { alert('fail') // if your PHP script return an erroneous header, you'll land here } }); }); </script> And php echo: <?php if ( $_POST ) { echo $_POST[ 'minValue' ]; } ?> Now why does it not echo the post? Thanks!

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