A part of my program relies on recording the lengths of roads within my user interface as they are drawn out. As this requires looping , and as I want to be able to keep the name of the list all the data is stored in the same, is it possible to create lists thusly :
set list road-length X
(where X is a counter that is incremented every time a condition is met). Essentially can I tag numbers on to the ends of lists so that I can tell them apart when they need to be read later on in my program?
You can, but it is almost surely the wrong approach. (For one thing, the names will not be global unless you declare them all ahead of time.) Instead, use the table extension, create a global to hold your table, and use the table to map your id numbers to your lists. This will prove much more useful.
Related
I have beeen constructing a model in Anylogic in the last weeks, and I am currently simulating the time a truck takes to deliver its products, so I used a delay for this in which different parameters are multiplied to several distributions. Is there any was I can keep track of the value of the distribution each time the process takes place. The following is in example:
normal(2, 8, 4.67, 1.96)*DropSize
The DropSize is my parameter, but I wish to know what value was generated for the normal distribution, and keep track of this.
Sure, several ways (as usual with AnyLogic :-) ). Here is one:
create a collection of type ArrayList:
Then, create a function that draws the random value, stores it in the collection and returns it as below:
Last, replace your code creating the random value with calling that function. Now, whenever you pull a value from the distribution, it is also stored in the collection.
cheers
I'm right now experimenting with a nodejs based experimental app, where I will be putting in a list of books and it will be posted on a forum automatically every x minutes.
Now my question is about order of these things posted.
I use mongodb (not sure if this changes the question or not) and I just add a new entry for every item to be posted. Normally, things are posted in the exact order I add them.
However, for the web interface of this experimental thing, I made a re-ordering interaction where I can simply drag and drop elements to reorder them.
My question is: how can I reflect this change to the database?
Or more in general terms, how can I order stuff in general, in databases?
For instance if I drag the 1000th item to 1st order, everything below needs to be edited (in db) between 1 and 1000 the entries. This does not seem like a valid and proper solution to me.
Any enlightenment is appreciated.
An elegant way might be lexicographic sorting. Introduce a String attribute for each item. Make the initial length of the values large enough to accomodate the estimated number of items. E.g., if you expect 1000 items, let the keys be baa, bab, bac, ... bba, bbb, bbc, ...
Then, when an item is moved from where it is to another place between two items, assign a value to the sorting attribute of the moved item that is somewhere equidistant (lexicographically) to those items. So to move an item between dei and dej, give it the value deim. To move an item between fadd and fado, give it the value fadi.
Keys starting with a were initially not used to leave space for elements that get dragged before the first one. Never use the key a, as it will be impossible to move an element before this one.
Of course, the characters used may vary according to the sort order provided by the database.
This solution should work fine as long as elements are not reordered extremely frequently. In a worst case scenario, this may lead to longer and longer attribute values. But if the movements are somewhat equally distributed, the length of values should stay reasonable.
I'd like to clear all application data from a single figure, without using the names of individual application data variables.
Is there any function in MATLAB that will do the above?
No, you can't do this in a simple way.
The application data for a figure is used to store lots of things by MATLAB itself (such as the zoom and pan status of the figure), not just things that you set yourself - so just "removing" it all is a bad idea.
You can get the full set of application data using getappdata(f), where f is the handle to the figure (as opposed to the more usual getappdata(f, 'varname'), which would get a specific variable that you'd stored in the application data).
The result is a structure, and you can than go through the field names and delete anything you've stored.
To make this easier, you can use a consistent prefix for the names of any variables you store. Then just go through the field names and call rmappdata for any field that starts with your prefix.
I got a part number field that have several repetitions. I want to use a variable to save this so that I can show all the descriptions of these parts in a different layout when user click a button.
But I do not know how to use variable to save several values like that. And I do not know exactly how many repetitions for each part number.
Although FileMaker allows for repetition fields and they have some valid behind-the-scenes uses for the database developer, they should NEVER be used for data. As pointed out by others, you should rethink you data structure.
That being said, you can capture the information in repeating fields by specifying which repetition you're interested in. If you have a repeating field named "partNumber" with 10 repetitions, then you can access each of the repetitions by:
partNumber[1]
partNumber[2]
.
.
.
partNumber[9]
partNumber[10]
RepFieldToVar [calculation] =Let($$varName = List(RepeatingFieldName), "")
This puts all repetitions into a return-delimited value list in $$varName.
Incidentally, there are _exceedingly rare_ instances where repeating fields are still useful. I've used them for grid-type schedule layouts that need stored values. But 99.98% of the time the other commenters are right, you can probably do it more efficiently with related records.
We would like to give each of users an alias so that we can refer to them in discussions while protecting their identity. These aliases should be unique.
The easy way would be to simply use a SERIAL column, but ints aren't memorable. We would like to use real people names so that we can remember the aliases.
The other easy way would be to find a list of first names somewhere, number them, and use a SERIAL to fetch names from the list. When the list runs out, add more names.
But is there some clever way to map ints to names?
We currently have about 2,000 users and are growing, but I doubt we'll ever become Google.
It may sound crazy. But there is an algorithm used in game programming to create meaningless but phonetically unique names like Alveolar, Bilabial, Glottal, Palatal, Velar.
Pick a random name from the Census Bureau's names file.
Have you tried any Hash functions? I am not sure whether they are available in Postgres. But yeah, one way to do is let the internal hash function take care. They will output unique IDs.
Back in "the day" Compuserve (or was it AOL?) used to give out temporary, initial passwords by having two lists of words and taking one word from each list and putting it together, so you would get something like EasyTomato or whatever. Perhaps something like that would work for your user base. If each word list has 256 characters, that's 65535 unique combinations (and notice how easily you can pick the combination by just incrementing a 16-bit integer).
EDIT: Well don't do a straight increment of the integer after all, or the first 256 people will all get the same first word, but the basic idea is still sound. Pick a random, not-yet-used 16-bit number. High 8 bits are your index into the first word list, low 8 bits are your index into the second word list.