Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>That would depend on whether you want to iterate over code units or code points. The language itself iterates over arrays by array elements, and strings are arrays of code units, so if you simply use <code>foreach</code> with type inference, then with</p> <pre><code>foreach(c; "La Verité") writeln(c); </code></pre> <p>the last two characters printed would be gibberish, because <code>é</code> is a code point made up of two UTF-8 code units, and you're printing out individual code units (since <code>char</code> is a UTF-8 code unit). Whereas, if you do</p> <pre><code>foreach(dchar c; "La Verité") writeln(c); </code></pre> <p>then the runtime will decode the code units to code points, and <code>é</code> will be printed as the last character. But none of this is really operating on strings as ranges. <code>foreach</code> operates on arrays natively without having to use the input range API. However, for all string types, the range API looks like</p> <pre><code>@property bool empty(); @property dchar front(); void popFront(); </code></pre> <p>It operates on strings as ranges of <code>dchar</code> - <em>not</em> their code unit type. This avoids issues with functions like <code>std.algorithm.filter</code> operating on individual code units, since that would make no sense. Operating on code points isn't 100% correct either, since Unicode gets very complicated with regards to combining code points and graphemes and whatnot, but operating on code points is far closer to being correct (and I believe there's work being done on adding range support for graphemes into the standard library for the cases where you need that and are willing to pay the performance hit). So, having the range API for strings operate on them as ranges of <code>dchar</code> is far more correct, and if you did something like</p> <pre><code>foreach(c; filter!"true"("La Verité")) writeln(c); </code></pre> <p>you would be iterating over <code>dchar</code>, and <code>é</code> would print correctly. The downside to all of this of course is the fact that <code>foreach</code> on strings operates on the code unit level by default whereas the range API for strings operate on them as code points, so you have to be careful when mixing array operations and range-based operations on strings. That's also why <code>string</code> and <code>wstring</code> are not considered random-access ranges - just bidirectional ranges. You can't do random access in O(1) on code points when they're made up of varying numbers of code units (whereas <code>dstring</code> <em>is</em> a random-access range, because with UTF-32, every code unit is a code point).</p>
    singulars
    1. This table or related slice is empty.
    1. POHow to read a string character by character as a range in D?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USJonathan M Davis
    1. USJonathan M Davis
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POHow to read a string character by character as a range in D?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COWhat happens if I import std.array which provides the needed Range-functions on UFCS level, will iterating over a string still be the same?
      singulars
      1. PO
      1. USdav1d
    2. CO@dav1d `foreach` on array will only ever use the array API. For arrays, the range-based functions must be used explicitly. And actually, as annoying as the inconsistency with foreach is, making its behavior depend on whether std.array was imported or not would be very bug-prone, since simply adding or removing that import could drastically change the behavior of your code depending on what it was doing.
      singulars
      1. PO
      1. USJonathan M Davis
    3. COYeah, I was really hoping it wouldn't change the code. But on the other hand UFCS allows iterating over objects which do not implement the opApply (might be wrong here) or range interface. Thanks for the clarification.
      singulars
      1. PO
      1. USdav1d
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload