On Saturday, 30 May 2015 at 23:58:44 UTC, Ali Çehreli wrote:
On 05/30/2015 12:19 PM, Dennis Ritchie wrote:
First, unfortunately, I don't understand you completely. Sorry
about that... :)
Nothing to worry about! Now you will understand me till the
end... :)
Regarding that, the intermediate range.front is already
available right before the .walk part. You can do anything at
that point. There was some proposals about a 'tap' algorithm
that could be used for debugging purposes. Here is a quick
implementation:
Yes, it is an intermediate stage of code that will help me to
explain what I want to get.
import std.stdio, std.algorithm;
static int idx;
void walk(R)(R range) {
while (!range.empty) {
range.front;
range.popFront;
}
}
struct Tap(alias func, R)
{
R range;
alias range this;
@property auto front()
{
func(range.front); // It's a necessary part of the
code! :)
return range.front;
}
}
auto tap(alias func, R)(R range)
{
return Tap!(func, R)(range);
}
void main() {
[5, 6, 7]
.map!(a => [idx++, a])
.tap!((a) { writeln(a[1..$]); }) /* <-- This can use
the
* lambda syntax as
well but
* note that the
return
* value of the
lambda is
* ignored. So I
think this
* syntax is more
* helpful. */
.walk;
}
Ali
I don't know, maybe it's something out of science fiction, but
here's what I want to do :)
struct Tap(alias func, R)
{
R range;
alias range this;
@property auto front()
{
immutable string myStr = `func(mixin("range.front"));`;
immutable string newStr = `mixin(myStr);`;
writeln(newStr); // I want them to be printed here
`writeln([5]);`
mixin(newStr[0 .. $ - 4] ~ `[idx,` ~ newStr[$ - 4 .. $]);
// I want them to be printed here `[0, 5];`
return range.front;
}
}
Is it possible to do using mixins or through any other means? Ie
I want to catch the moment when `func` is replaced by the
invocation of `writeln` :)
