What's a string?

Question

If a challenge says that input will be in the form of a string, what is acceptable?

Various languages have different ways of implementing strings, so here's what I've "borrowed" from Wikipedia:

In computer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable.

The reason I ask is that my most frequently used language here is Java. Of course, Java has a String class, and that's what I've been using. However, I've run into a couple situations where a char[] would be better.

In my opinion, while a char[] is not a String, it is a "string".

Say I have a challenge that reads:

Write a function that takes a string (printable ASCII) as input, adds 1 to each character, and returns it (don't worry about overflow)

While this is a trivial example, String is crap here.

• It's not mutable, so I need a new one to return.
• To access a character you have to use .charAt(i) instead of [i]
• .length() is two bytes longer than .length
• Once you add, you have to cast it back to char or it converts to an integer:

An example of both types:

String a(String a){String b="";for(int i=0;i<a.length();b+=(char)(a.charAt(i++)+1));return b;}

char[]a(char[]a){for(int i=0;i<a.length;a[i++]++);return a;}

I haven't looked much to see if I can reduce either of these, but the point remains; there's no way the String version is coming out ahead.

Of course, in some situations String has the upper hand. If you need indexOf(), trim(), or easy conversion from literals, you'd want that.

Since both a String and a char[] are strings by most reasonable definitions of the word, I believe it shouldn't matter which is used. In addition, having to choose between the two makes for a different golf process than sticking to one or the other.

Don't get me wrong. I'm not saying that I've seen any argument/debate about this on the site, but I've personally held back from using char[] where it asks for a string, and I just got around to wondering why. Either way, I think it would make a good Standard Definition, and I'd like some input.

Answer 1

I agree with the wikipedia definition. It's a sequence of characters. As the name suggests, it's one-dimensional. I program a lot in C and sometimes in Pascal, which both implement strings in different ways.

C doesn't have a string type, only char[] with a string by convention being terminated by a zero byte.

Original Pascal has a String type which has a maximum length of 255, because the length of s[] is stored in s[0].

More recently more advanced versions of these languages have been released, with more advanced string types. I frequently see C++ answers with both std::string and char[] and I see no problem with that.

Brainfuck and assembly language have no types, yet clearly both can handle "strings" according to the wikipedia definition. So I would define it as a sequence of characters and leave it at that.

What I do think question posters need to define, is what is a character, i.e. whether only ASCII or full unicode can be expected as input. I can think of one recent example where a poster stated that input would be ASCII only, but included a Euro sign in a test case (he later changed it to a dollar sign.) This is perhaps even more important for defining the winning criterion. Where questions specify that program length is by characters, it is good to see that many posters are now linking pages like https://mothereff.in/byte-counter in their questions, which removes any ambiguity.

Answer 2

If it looks like a string and acts like a string, it's a string

Examples of strings:

• Native string types: C++ strings, Java Strings, JavaScript Strings, etc.
• Native character types: C/C++ chars and wchars, Java chars and Characters, etc.
• An iterable (tuple, array, vector, list, etc.) of characters or length-1 strings: C/C++/Java/etc. char[]s, a list of length-1 strings in Python ([x for x in s]), etc.
• An iterable of byte values (between 0 and either 127 or 255, inclusive, depending on whether or not extended ASCII is supported): Python 3's bytes type, brainfuck's tape (when given ASCII input)
• An iterable of integers representing Unicode code points (SWI-Prolog does this)

Answer 3

A string is also a list of single character strings. For example:

["H", "e", "l", "l", "o", ",", " ", "w", "o", "r", "l", "d", "!"]

While technically different, this is not thematically different from a list of characters. Therefore I believe agrees with the current consensus' conclusion that the Wikipedia definition of "a sequence of characters". I don't believe this format encodes any more information than a plain string does.

Sometimes certain operations in higher level languages are more convenient when performed on a list in this manner, and I don't see why we should automatically limit some of the opportunities that people can have for golfing or otherwise improving their score.

Answer 4

You're over-thinking the problem. Unless the challenge specifically states that you must use the native "string" type of the language, you get to interpret what "string" means in a way that's most advantageous to your implementation.

Answer 5

If a language makes a distinction between char[] and String, I think a good question to ask is "Does a char[] print like a string?" If it is possible to print a char[] so that it looks like String, then you can use it. Many questions give the option of printing or returning the output, so I think the returned output should look similar to the printed output if it were printed.

Let's say that the challenge allowed you to write a function that returns a string. Java, for example, has both a String and a char[]. If you use System.out.println() to print the char[], then it is formatted and looks the same as if you had printed a String (Ideone example). This means that it will be acceptable for the method to return either a String or a char[].

Here is some psuedocode to demonstrate how this can be tested. You are allowed to modify the print method, such as using println, but you can't modify the golfed method's output before it is fed into the print.

class tester{
  main(n){
    print(f(n));
  }
  char[] f(n){
    //golf code here
  }
}

If there is a language that does not allow a char[] to be easily printed, meaning that it always looks like [a, b, c] or ['a', 'b', 'c'] regardless of the type of printing method you use, then I don't think char[] is an acceptable substitute.