Ask General Programming Questions Not Worth Their Own Thread

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csammis: Aug 26, 2003; Mental Institution

Goodness the old one had been going a long time

A Paradigm Shift: This thread is now for generic questions about coding, and language-neutral short programming questions (or languages for which there isn't already a megathread). If you've got a question about a specific language, and there's a megathread for it, better to post it there where the language-specific ~~dorks~~ experts will see it.

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csammis fucked around with this message at Oct 22, 2012 around 11:49

# ? Feb 22, 2008 15:13

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# ? May 20, 2013 08:20

csammis: Aug 26, 2003; Mental Institution

Let's get this party started:

Jose Cuervo posted:

poopiehead, do you know of a good way to search for a particular key in a dictionary without actually knowing the key, but only a unique characteristic? I know that the key I am looking for is the one the has the longest string length (and there is a key with a longest string length in my dictionary). Right now I am useing the following loop to get the key:
code:
         For Each key As String In myDic.Keys
            If key.Length > theLongestKey.Length Then
               theLongestKey = key
            End If
         Next
where I initially have theLongestKey set as an empty string. This works, but I thought there might be a cleverer (and hopefully more efficient) way to do it.

Note, this is a good example of a question that belongs in this thread because it's language-agnostic

Iterating through the keys to find what you're looking for is the only way to do it at any given time, unless you want to use a "compiler solution" and throw another list at it that consists the keys sorted by the property you want, which you would add to whenever you insert a new key into the dictionary. I can't really imagine that there's a good reason to do this.

But along those lines: Wherever you're adding an entry to the dictionary, how about you just add a check to see if the key that's being added satisfies the property you want, and save it?

# ? Feb 22, 2008 15:23

Jose Cuervo: Aug 25, 2004

csammis posted:

But along those lines: Wherever you're adding an entry to the dictionary, how about you just add a check to see if the key that's being added satisfies the property you want, and save it?

I think I am going to go with this method. On a related note, (although this is VB specific), if I wanted an array or a dictionary to be accessible by any function in any part of my code (even if it is in a different class), what would I need to put in my main to do that?

I would prefer the array/dictionary to be read only, but this is not crucial.

# ? Feb 22, 2008 15:41

Save the whales: Aug 30, 2004; by T. Finn

I'll state my question using Java terminology, but I'm curious as to whether there's a general name for this kind of data structure.

Recently I came upon the need for a data structure that is a bit of a cross between a Map and a Set. I ended up calling it BinaryRelation<L, R>. Its most important methods are:

code:

/*
pairs the given left-hand and right-hand values
*/
void put(L left, R right);

/*
returns a collection view of the left-hand values paired with the specified right-hand value
*/
Collection<L> getLeft(R right);

/*
returns a collection view of the right-hand values paired with the specified left-hand value
*/
Collection<R> getRight(L left);

It's kind of like a bidirectional map in that you can find associated values for keys or associated keys for values, but it's different in that neither keys nor values must be unique - only key-value pairs must be unique.

I've already written the Java code to implement this, so I'm not asking how it can be done, but I'm curious - is there a general name for this kind of data structure? Has it been implemented in any popular programming languages or libraries? I wasn't able to find anything like this after a bit of Googling and I was surprised because it seems like such a useful way of describing a relation between two sets of objects. I know for certain I'm going to use it in every web application I make from here on out.

# ? Feb 23, 2008 07:14

zootm: Aug 8, 2006; We used to be better friends.

That kind of relationship is referred to as "many-to-many" but I'm not sure what a data structure that implements it would be called. I've only ever seen this sort of thing in persistence libraries modelling the same thing in a database, but they don't tend to use a specialised structure. With one-to-one multiplicity this would be a "bidirectional map", but that's not what you've done here. Essentially you're just holding a list of graph edges with a specialised interface to it, as far as I can tell?

Edit: That last one basically answered itself. I think the data structure you've made is probably pretty much a graph data structure, and you could implement your interface with an adjacency list or an adjacency matrix pretty well. The interface just looked kinda strange

. Since you differentiate left and right I guess you're essentially representing a directed graph as well.

zootm fucked around with this message at Feb 23, 2008 around 09:32

# ? Feb 23, 2008 09:23

fret logic: Mar 8, 2005; roffle

What are some good resources/books on programming theory?

# ? Feb 24, 2008 07:38

6174: Dec 4, 2004

fret logic posted:

What are some good resources/books on programming theory?

What aspect are you interested in? Algorithms? Data structures? Programming Languages (either specific language or in general)? Program design? Numerical Analysis? Operating Systems? Something else?

Also a bit about your background may help so you don't get recommended something that is either too simple or too hard.

# ? Feb 24, 2008 07:55

fret logic: Mar 8, 2005; roffle

6174 posted:

What aspect are you interested in? Algorithms? Data structures? Programming Languages (either specific language or in general)? Program design? Numerical Analysis? Operating Systems? Something else?

Also a bit about your background may help so you don't get recommended something that is either too simple or too hard.

I'm just a CS freshman with little to no background in anything beyond basic Java/C syntax. Was just wanting to get some basic theory in my head while I'm learning these languages.

# ? Feb 24, 2008 08:24

6174: Dec 4, 2004

fret logic posted:

I'm just a CS freshman with little to no background in anything beyond basic Java/C syntax. Was just wanting to get some basic theory in my head while I'm learning these languages.

In that case I'd recommend two books. First, The Practice of Programming by Kernighan and Pike. It will help get some good practices in your head and is a good choice for someone still pretty new to programming. Second is Code Complete by McConnell. It is a handbook of practical advice.

# ? Feb 24, 2008 08:29

Avenging Dentist: Oct 1, 2005; oh my god is that a circular saw that does not go in my mouth aaaaagh

fret logic posted:

I'm just a CS freshman with little to no background in anything beyond basic Java/C syntax. Was just wanting to get some basic theory in my head while I'm learning these languages.

If you want some "deep" theory, check out Knuth's "Art of Computer Programming" series (be warned, they are very, very math-heavy).

# ? Feb 24, 2008 08:41

fret logic: Mar 8, 2005; roffle

6174 posted:

In that case I'd recommend two books. First, The Practice of Programming by Kernighan and Pike. It will help get some good practices in your head and is a good choice for someone still pretty new to programming. Second is Code Complete by McConnell. It is a handbook of practical advice.

I'll check those out, thanks! Should I wait until I have a language down pretty well to read Code Complete?

Avenging Dentist posted:

If you want some "deep" theory, check out Knuth's "Art of Computer Programming" series (be warned, they are very, very math-heavy).

# ? Feb 24, 2008 08:50

duck monster: Dec 15, 2004; Never stop arguing about casual racism.

Avenging Dentist posted:

If you want some "deep" theory, check out Knuth's "Art of Computer Programming" series (be warned, they are very, very math-heavy).

This book is the Computer science version of Walter Pistons "Counterpoint" and "Harmony" , THE canonical bibles on music theory, but also complete brainfucks for people first reading them.

If you DO struggle through Knuth's works, do so reverently, Knuth may be hard , but you get that when dealing with the sacred texts of God himself.

# ? Feb 24, 2008 09:13

Professor Science: Mar 8, 2006; diplodocus + mortarboard = party

Avenging Dentist posted:

If you want some "deep" theory, check out Knuth's "Art of Computer Programming" series (be warned, they are very, very math-heavy).

Oh that series that people have on their bookshelf so they can be like, "Oh, yes, I've read the Art of Computer Programming, yessssss, I am smoking a pipe now?"

# ? Feb 24, 2008 09:20

6174: Dec 4, 2004

fret logic posted:

I'll check those out, thanks! Should I wait until I have a language down pretty well to read Code Complete?

If you've taken a course or two of programming, you'll be adequately prepared for a large chunk of Code Complete. Of course if you have less experience it may take longer to wade through, but with some motivation you could do it.

Also a note about Knuth's books. They are very good, but I'm not sure Avenging Dentist's warning is quite strong enough. To be able to digest any of it you'll want to have at least some experience with discrete math (proof techniques, some set theory, etc) and algorithms/data structures. For many topics TAOCP is the best reference you'll find. However it is very dense, and not really friendly to someone just starting out. I'd strongly recommend you look at a copy from the library before you even think of anything like buying them. If you look at them and find them to be too much, look for the book Concrete Mathematics by Graham et al. It is designed to contain the math one needs to tackle TAOCP and would be a good intermediary step (and I'd still recommend some discrete math before tackling Concrete Mathematics).

# ? Feb 24, 2008 09:23

csammis: Aug 26, 2003; Mental Institution

Professor Science posted:

Oh that series that people have on their bookshelf so they can be like, "Oh, yes, I've read the Art of Computer Programming, yessssss, I am smoking a pipe now?"

Has this man read TAOCP?

# ? Feb 24, 2008 15:37

poopiehead: Oct 6, 2004

Since you've already done some C, I'll recommend The C Programming Language. A lot of it will just be review, but it makes some things you might have a foggy understanding more precise and it's actually incredibly concise and accessible.

Depending on where you're going with CS, Mythical Man Month, Extreme Programming Explained, and Pragmatic Programmer are pretty great reads more focused on programming as a profession/art than CS theory. Probably want to wait a year or two for these or at least re-read in a few years though, not because they're hard(they're not), but because more experience puts them into context.

# ? Feb 24, 2008 15:42

Alan Greenspan: Jun 17, 2001

fret logic posted:

I'm just a CS freshman with little to no background in anything beyond basic Java/C syntax. Was just wanting to get some basic theory in my head while I'm learning these languages.

http://www.cs.rochester.edu/~scott/pragmatics/
http://www.amazon.com/Programming-L...t/dp/1558604421

This book is extremely awesome.

# ? Feb 24, 2008 18:46

Ranma: Nov 2, 2004; God I fucking love Diablo 3 gold, it even paid for this shitty title

What is a good book to learn database programming? I am starting a co-op where they do SQL programming, and we're coding with Java. I have no experience with SQL or database programming.

# ? Feb 24, 2008 20:07

IcePotato: Dec 29, 2003; There was nothing to fear
Nothing to fear

Rheingold posted:

http://www.cs.rochester.edu/~scott/pragmatics/
http://www.amazon.com/Programming-L...t/dp/1558604421

This book is extremely awesome.

Agreed, and the author is a great professor to boot

# ? Feb 24, 2008 21:46

Scaevolus: Apr 16, 2007

fret logic posted:

What are some good resources/books on programming theory?

Structure and Interpretation of Computer Programs

# ? Feb 24, 2008 23:51

Gesundheit: Sep 19, 2007

Scaevolus posted:

Structure and Interpretation of Computer Programs

Seconding this. Especially for a beginner who has only learnt an imperative language yet.

# ? Feb 25, 2008 00:39

Mustach: Mar 2, 2003; In this long line, there's been some real strange genes. You've got 'em all, with some extras thrown in.