Hi all,

I'm Merlin, I'm just starting out in D and super excited.

My questions are:-

1. In a range pipeline how does one handle the event of a filter range returning empty?

2. How does one unwrap a single result from a range operation?

Look forward to your assistance!

Merlin

On Friday, 27 August 2021 at 01:51:42 UTC, Merlin Diavova wrote:

1. you don't have to handle it.
   it just won't go.

2. takeOne put it into the search on the dlang site

On Friday, 27 August 2021 at 02:10:48 UTC, Stefan Koch wrote:

Thanks for the quick response!

Took a look at takeOne and yep that's the ticket.

What I meant about the handling an empty filter is, what if I want to take an alternative route if the filter returns empty?

On 8/26/21 7:17 PM, Merlin Diavova wrote:

Then the operations downstream will not produce any results. For example, the array will be empty below:

import std.stdio;
import std.range;
import std.algorithm;
import std.string;
import std.functional;

void main() {
auto significantLines = stdin
.byLineCopy
.map!strip
.filter!(not!empty)
.filter!(line => line.front != '#')
.array;

if (significantLines.empty) {
writeln("There were no significant lines.");

} else {
writefln!"The lines: %-(\n%s%)"(significantLines);
}
}

Ali

On Friday, 27 August 2021 at 04:01:19 UTC, Ali Çehreli wrote:

And there it is!

I was missing

.filter!(not!empty)

My code now works exactly how I wanted. Thanks!