Re: A little help with Ranges
On 8/27/21 12:41 AM, Merlin Diavova wrote:
On Friday, 27 August 2021 at 04:01:19 UTC, Ali Çehreli wrote:
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
And there it is!
I was missing
```d
.filter!(not!empty)
```
My code now works exactly how I wanted. Thanks!
Be careful with this! `not!empty` is *only* working because you are
using arrays (where `empty` is a UFCS function defined in std.range).
Other ranges this will not work on. Instead, I would recommend a lambda
(which will work with arrays too):
```d
.filter!(r => !r.empty)
```
-Steve
Re: A little help with Ranges
On Friday, 27 August 2021 at 04:01:19 UTC, Ali Çehreli wrote:
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
And there it is!
I was missing
```d
.filter!(not!empty)
```
My code now works exactly how I wanted. Thanks!
Re: A little help with Ranges
On 8/26/21 7:17 PM, Merlin Diavova wrote:
What I meant about the handling an empty filter is, what if I want to
take an alternative route if the filter returns empty?
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
Re: A little help with Ranges
On Friday, 27 August 2021 at 02:17:21 UTC, Merlin Diavova wrote: On Friday, 27 August 2021 at 02:10:48 UTC, Stefan Koch wrote: On Friday, 27 August 2021 at 01:51:42 UTC, Merlin Diavova wrote: 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 1. you don't have to handle it. it just won't go. 2. `takeOne` put it into the search on the dlang site 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? You check if it's by calling empty. or do you want a default value? I am sure there is a convince function for that somewhere in phobos.
Re: A little help with Ranges
On Friday, 27 August 2021 at 02:10:48 UTC, Stefan Koch wrote: On Friday, 27 August 2021 at 01:51:42 UTC, Merlin Diavova wrote: 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 1. you don't have to handle it. it just won't go. 2. `takeOne` put it into the search on the dlang site 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?
Re: A little help with Ranges
On Friday, 27 August 2021 at 01:51:42 UTC, Merlin Diavova wrote: 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 1. you don't have to handle it. it just won't go. 2. `takeOne` put it into the search on the dlang site
A little help with Ranges
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
