On Tuesday 08 September 2015 19:52, Matt Kline wrote:
> An example:
>
> import std.algorithm;
> import std.range;
> import std.stdio;
> import std.regex;
>
> void main()
> {
> // One would expect this to be a range of chars
> auto test = chain("foo", "bar", "baz");
> // prints "dchar"
> writeln(typeid(typeof(test.front)));
>
> auto arr = ["foo", "bar", "baz"];
> auto joined = joiner(arr, ", ");
> // Also "dchar"
> writeln(typeid(typeof(joined.front)));
>
> // Problems ensue if one assumes the result of joined is a
> char string.
> auto r = regex(joined);
> matchFirst("won't compile", r); // Compiler error
> }
>
> Whether by design or by oversight,
By design with regrets:
http://forum.dlang.org/post/m01r3d$1frl$1...@digitalmars.com
> this is quite undesirable. It
> violates the principle of least astonishment (one wouldn't expect
> joining a bunch of strings would result in a dstring),
The result is a range of dchars actually, strictly not a dstring.
> causing
> issues such as the one shown above. And, if I aim to use UTF-8
> consistently throughout my applications (see
> http://utf8everywhere.org/), what am I to do?
You can use std.utf.byCodeUnit to get ranges of chars:
----
import std.algorithm;
import std.array: array;
import std.range;
import std.stdio;
import std.regex;
import std.utf: byCodeUnit;
void main()
{
auto test = chain("foo".byCodeUnit, "bar".byCodeUnit, "baz".byCodeUnit);
pragma(msg, typeof(test.front)); /* "immutable(char)" */
auto arr = ["foo".byCodeUnit, "bar".byCodeUnit, "baz".byCodeUnit];
auto joined = joiner(arr, ", ".byCodeUnit);
pragma(msg, typeof(joined.front)); /* "immutable(char)" */
/* Having char elements isn't enough. Need to turn the range into an
array via std.array.array: */
auto r = regex(joined.array);
matchFirst("won't compile", r); /* compiles */
}
----
Alternatively, since you have to materialize `joined` into an array anyway,
you can use the dchar range and make a string from it when passing to
`regex`:
----
import std.algorithm;
import std.conv: to;
import std.stdio;
import std.regex;
void main()
{
auto arr = ["foo", "bar", "baz"];
auto joined = joiner(arr, ", ");
pragma(msg, typeof(joined.front)); /* "dchar" */
/* to!string now: */
auto r = regex(joined.to!string);
matchFirst("won't compile", r); /* compiles */
}
----
