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digitalmars.D.learn - Inconsistent chain (implicitly converts to int)

reply Salih Dincer <salihdb hotmail.com> writes:
Hi everyone,

Technically r1 and r2 are different types of range. Isn't it 
inconsistent to chain both? If not, why is the char type 
converted to int?

```d
import std.stdio,
        std.range;

void main() {
   auto r1 = N!size_t(10, 1, 1);
   auto r2 = N!real(15, .5, 10);

   r1.chain(r2).writeln;
   // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 
13, 13.5, 14, 14.5]

   auto a = [97, 98, 99];
   auto b = ['d', 'e', 'f'];

   a.chain(b).writeln;
   // [97, 98, 99, 100, 101, 102]
}

struct N(T)
{
   T last, step, first;
   bool empty() => first >= last;
   T front() => first;
   auto popFront() => first += step;
}
void main() {
   auto r1 = N!size_t(10, 1, 1);
   auto r2 = N!real(15, .5, 10);

   r1.chain(r2).writeln;
   // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 
13, 13.5, 14, 14.5]

   auto a = [97, 98, 99];
   auto b = ['d', 'e', 'f'];

   a.chain(b).writeln;
   // [97, 98, 99, 100, 101, 102]
}

struct N(T)
{
   T last, step, first;
   bool empty() => first >= last;
   T front() => first;
   auto popFront() => first += step;
}
```

SDB 79
Apr 05 2024
parent reply "H. S. Teoh" <hsteoh qfbox.info> writes:
On Fri, Apr 05, 2024 at 03:18:09PM +0000, Salih Dincer via Digitalmars-d-learn
wrote:

 Hi everyone,
 
 Technically r1 and r2 are different types of range. Isn't it
 inconsistent to chain both? If not, why is the char type converted to
 int?


[...]

It's not inconsistent if there exists a common type that both range
element types implicit convert to.

The real problem is the implicit conversion of char to int, which I have
been against for a long time.  Walter, however, disagrees.


T

-- 
What's worse than raining cats and dogs?  Hailing taxis!
Apr 05 2024
next sibling parent reply rkompass <rkompass gmx.de> writes:
On Friday, 5 April 2024 at 16:05:20 UTC, H. S. Teoh wrote:

 On Fri, Apr 05, 2024 at 03:18:09PM +0000, Salih Dincer via 
 Digitalmars-d-learn wrote:

 Hi everyone,
 
 Technically r1 and r2 are different types of range. Isn't it 
 inconsistent to chain both? If not, why is the char type 
 converted to int?


 [...]

 It's not inconsistent if there exists a common type that both 
 range element types implicit convert to.


In the first example the int's are converted to doubles (also 
common type).
But they appear as int's because writeln does not write a 
trailing .0.
Apr 05 2024
parent reply Salih Dincer <salihdb hotmail.com> writes:
On Friday, 5 April 2024 at 21:16:42 UTC, rkompass wrote:

 In the first example the int's are converted to doubles (also 
 common type).
 But they appear as int's because writeln does not write a 
 trailing .0.


But it doesn't work as you say! I even tried it on an older 
version and got the same result.

SDB 79
Apr 05 2024
parent reply rkompass <rkompass gmx.de> writes:
On Friday, 5 April 2024 at 21:26:10 UTC, Salih Dincer wrote:

 On Friday, 5 April 2024 at 21:16:42 UTC, rkompass wrote:

 In the first example the int's are converted to doubles (also 
 common type).
 But they appear as int's because writeln does not write a 
 trailing .0.


 But it doesn't work as you say! I even tried it on an older 
 version and got the same result.

 SDB 79


I checked:

```d
import std.stdio,
        std.range,
        std.algorithm;

struct N(T)
{
   T last, step, first;
   bool empty() => first >= last;
   T front() => first;
   auto popFront() => first += step;
}

void main() {
   auto r1 = N!size_t(10, 1, 1);
   auto r2 = N!real(15, .5, 10);

   // r1.chain(r2).writeln;
   // [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10.5, 11, 11.5, 12, 12.5, 
13, 13.5, 14, 14.5]
   r1.chain(r2).map!(x => typeid(x)).writeln;
   // [real, real, . . . , real]
}
```
and it seems to work as I said.
Apr 06 2024
parent Salih Dincer <salihdb hotmail.com> writes:
On Saturday, 6 April 2024 at 09:21:34 UTC, rkompass wrote:

 I checked:

 ```d
 import std.stdio,
        std.range,
        std.algorithm;

 struct N(T)
 {
   T last, step, first;
   bool empty() => first >= last;
   T front() => first;
   auto popFront() => first += step;
 }

 void main() {
   auto r1 = N!size_t(10, 1, 1);
   auto r2 = N!real(15, .5, 10);
 ```
 and it seems to work as I said.


Thank you for checking again, but it is important to be solution 
oriented. How about Tuple?

Yes, it might be wise to use a tuple in this case:
```d
   //...
   auto tuple = a.zip(b);
   tuple.writeln;
   // [Tuple!(int, dchar)(97, 'd'), Tuple!(int, dchar)(98, 'e'), 
Tuple!(int, dchar)(99, 'f')]

   tuple.map!(num => num[0].to!dchar).write;
   tuple.map!"a[1]".writeln; // abcdef
}
```

SDB 79
Apr 06 2024
prev sibling parent Salih Dincer <salihdb hotmail.com> writes:
On Friday, 5 April 2024 at 16:05:20 UTC, H. S. Teoh wrote:

 On Fri, Apr 05, 2024 at 03:18:09PM +0000, Salih Dincer via 
 Digitalmars-d-learn wrote:

 Hi everyone,
 
 Technically r1 and r2 are different types of range. Isn't it 
 inconsistent to chain both? If not, why is the char type 
 converted to int?


 [...]

 It's not inconsistent if there exists a common type that both 
 range element types implicit convert to.

 The real problem is the implicit conversion of char to int, 
 which I have been against for a long time.  Walter, however, 
 disagrees.


 T


```d
   auto a = [97, 98, 99];
   auto b = ['d', 'e', 'f'];

   a.chain(b).map!(chr => chr.to!char).writeln;
   // abcdef
```

Nice, there is a solution that requires memory allocation, but it 
still makes you think!

However, they can fix this in Phobos3 because now we have this 
too: 
https://dlang.org/changelog/2.108.0.html#range_predicate_element

PS. I think I unintentionally made a chain by repeating the 
source code above, sorry :)

SDB 79
Apr 05 2024