Re: linear search using 'find' on an array of structs?

[captain_fid]

On Sunday, 9 March 2014 at 10:46:26 UTC, Philippe Sigaud wrote:
        assert(!find!("toLower(a) == b")(s, "hello").empty);
        assert(!find!("toLower(a) == b")(clist.name, 
"name2").empty);


But clist is an array of c's, it has no `.name` field by 
itself. So, put
the `.name` call inside the comparator:


 assert( find!("toLower(a.name) == b")(clist 
<http://clist.name/>*,*
 "name2").empty);

This gives me this code:

import std.algorithm: find;
import std.array: empty;
import std.uni: toLower;

struct C // Use UpperCase for you user-defined types
{
  int idx;
  string name;
}

C[] clist = [ {1, "name1"}, {2, "name2"}, { 3, "name3" } ];

void main() // no need to return 0
{
  auto target = clist.find!((a,b) => toLower(a.name) == 
b)("name2");
  assert(!target.empty);
}

Using UFCS (Universal Function Call Syntax) to tranform f(a,b) 
into a.f(b).
I used it on `find`.



I went looking to replace several foreach statements. Can 
'find' (in
understand it's just a linear search) be used on an array of 
structures
like above.


Sure, as long as you tell it how you will get the info from the 
range (it
defaults to simple equality).




Example pulled and modified. Above code gives me (naturally) -
  ... no property 'name' for type 'cp[]'.

Interestingly, I had accidentally coded the commented out line 
before and
it compiles correctly but will (as you guessed it) fail.


I never use pointers in D. I suppose the `.name` call is 
propagated to the
array elements?

Thanks for the simple explanation Phillppe. Someone else 
mentioned before not using pointers in D (the loss of array 
goodness like mentioned in Andrei's book). Bad habits...