Adding item to a rbtree with a custom binaryFun

[Steven Schveighoffer]

On 4/13/20 7:59 PM, Adnan wrote:
> I want to keep an ordered set of records and the standard provides me 
> with RedBlackTree. The record is of type Tuple!(string, uint). Here's 
> what it looks like:
> 
> import std.json : parseJSON;
> 
>      uint[string] wordTable;
>      import std.datetime.stopwatch : StopWatch, AutoStart;
> 
>      auto sw = StopWatch(AutoStart.yes);
>      const auto j = parseJSON(get(link));
>      const long downloadTime = sw.peek.total!"msecs";
> 
>      import std.typecons : Tuple, tuple;
>      import std.container.rbtree : RedBlackTree;
>      import std.functional : binaryFun;
>

// instead of this:

>      RedBlackTree!(Tuple!(string, uint), binaryFun!("a[1] > b[1]")) 
> records;

// do this: (note you don't need binaryFun)
        auto records = new RedBlackTree!(Tuple!(String, uint), "a[1] > 
b[1]");

> 
>      foreach (node; j["posts"].array()) {
>          import std.stdio : writeln;
>          import std.utf : decode;
> 
>          if ("com" in node) {
>              import std.algorithm : splitter;
> 
>              foreach (word; getStr(node["com"].str()).splitter(' ')) {
>                  import std.string : strip;
> 
>                  if (word.strip().length > 0)
>                      wordTable.require(word, 0)++;
> 
>                  records ~= (tuple(word, wordTable[word])); // error
>              }
>          }
>      }
> 
> Now primarily I used `insert()` method to add a record to the records 
> but it causes segfault in runtime.

Because RedBlackTree is a class, so you need to initialize it with a 
call to new.

> So I decided to use ~= to see what's 
> going on. Here's what the compiler says:
> 
> Error: cannot append type Tuple!(string, uint) to type 
> std.container.rbtree.RedBlackTree!(Tuple!(string, uint), binaryFun, false)

Because RedBlackTree doesn't overload appending.

-Steve