A sudden insight

Originally published on 15 October 2010 by Carl Mäsak.

Sometimes things seem to click and fall into place inside my brain. Previously unrelated concepts turn out to be have commonalities after all.

For example, I said yesterday on #raku that I’d realized, teaching Perl, that taking away wantarray was only a logical next step after taking away sigil variance. Moritz was way ahead of me, though: he had blogged about exactly this a year ago.

But a much deeper insight hit me on the Sunday, when jnthn++ was talking, and explaining how Captures and Signatures form two sides of a function call binding:

 caller                     callee
Capture <---> binder <---> Signature

and then showing a slide that looked like this:

my ($some, $random, $things) := some-`function`;

The point of the slide is that Signatures aren’t just used in function declarations; they’re used in the above case as well. I’ve always thought that this was a random, fortuitous bonus use of it…

…but then Liz turned to me and whispered “that’s because return is just another function call”. And right then and there, I went through some sort of mini-enlightenment. How beautiful!

Later, Liz divulged that this was the kind of insight that came naturally when one had programmed in continuation-passing style for a while. It’d be interesting to learn whether CPS is the reason for ```rakuSignature`s being used in bindings like this in Raku. For some reason, my guess is no.

Anyway, Raku surprising me with its consistency is only appropriate, given the name of this blog.