Retina

Cᴏɴᴏʀ O'Bʀɪᴇɴ

19:59

Eyes!

(Get it. Retina)

Martin Ender

@CᴏɴᴏʀO'Bʀɪᴇɴ Message closed as off-topic.

(I see the potential for confusion though...)

Bálint

I have problems with my retina. Where should I go first?

FryAmTheEggman

Hmm, did anyone ever answer the identity matrix question in retina?

Martin Ender

@FryAmTheEggman link?

Cᴏɴᴏʀ O'Bʀɪᴇɴ

oh, that one

24

Q: Construct the Identity Matrix

The challenge is very simple. Given an integer input n, output the n x n identity matrix. The identity matrix is one that has 1s spanning from the top left down to the bottom right. You will write a program or a function that will return or output the identity matrix you constructed. Your output ...

FryAmTheEggman

20:00

Yeah

Cᴏɴᴏʀ O'Bʀɪᴇɴ

I'm still learning retina, don't know quite how to tackle that

FryAmTheEggman

Looks like Digital Trauma did

Martin Ender

apparently I also helped golf it

Cᴏɴᴏʀ O'Bʀɪᴇɴ

I wonder if $* could be used here

Of course, that was added after the challenge

Martin Ender

well it already takes unary input...

Cᴏɴᴏʀ O'Bʀɪᴇɴ

20:03

yeah

oh, wait, I misunderstood $* :P

FryAmTheEggman

Yeah and I don't think it'll help because the numbers have to be separated

Might have been a cheeky way to generate all the zeros, otherwise?

Cᴏɴᴏʀ O'Bʀɪᴇɴ

true

Martin Ender

well you can do something like this: retina.tryitonline.net/#code=XEIKJC5fJCow&input=MTExMQ ... now how to the lines...

FryAmTheEggman

Maybe there's a way to combine it with the first line to still have a capture group with the length or something?

Although that seems like it would be too long...

Cᴏɴᴏʀ O'Bʀɪᴇɴ

is there a way to include $* in the first part of a replace stage?

if not, it could be kind of a cool thing to match something n times, where n is some part of the string

FryAmTheEggman

20:15

Uh, you mean the pattern line? If so, then no :(

Cᴏɴᴏʀ O'Bʀɪᴇɴ

yeah, the pattern line

FryAmTheEggman

I dunno so far there haven't been any "exec" like things that Martin's added, they may only be coming much later or something.

Probably better to ask Martin though, I guess :P

Cᴏɴᴏʀ O'Bʀɪᴇɴ

True. Any input, Martin?

ninja'd

Martin Ender

well yeah... that's pretty far down the line... anything that can be implemented via compiling to .NET regex is a bit more likely. but even for that I'd need to tokenise .NET regex which I'm not really looking forward to

you can match something n times (where n is something in the string) but it requires balancing groups which are too expensive in this case

so yeah I guess something like this could be compiled to .NET regex

Cᴏɴᴏʀ O'Bʀɪᴇɴ

my best attempts at this don't work at all :P

Martin Ender

20:20

well this works, but it's way too long: retina.tryitonline.net/…

I first count the number of 1s in a lookaround and then I match that many characters

Cᴏɴᴏʀ O'Bʀɪᴇɴ

oo, cool

FryAmTheEggman

I was working on something similar, but I noticed that the 0 that you should split on has the same number of 0s directly before it as 1s anywhere after it

Cᴏɴᴏʀ O'Bʀɪᴇɴ

I have this but it only works for fixed N

FryAmTheEggman

but I think it's also gonna be way to long

Martin Ender

@FryAmTheEggman ohhh

hm yeah but with "exactly that many" it's hard to avoid something like (?(1)!)

FryAmTheEggman

20:25

Yeah that's what I've been struggling with

Cᴏɴᴏʀ O'Bʀɪᴇɴ

I should probably learn .NET regex :P

Martin Ender

best I'm coming up with right now: retina.tryitonline.net/…

@CᴏɴᴏʀO'Bʀɪᴇɴ I suppose you've been linked to my SO answer on balancing groups before?

Cᴏɴᴏʀ O'Bʀɪᴇɴ

yes, I have.

Martin Ender

(or stumbled over it in one of Retina answers)

Cᴏɴᴏʀ O'Bʀɪᴇɴ

I get the concept, but I couldn't replicate

Martin Ender

20:27

the answers to the regex golf CnR also help understanding what's possible with balancing groups

a lot of them used them to implement some form arithmetic

FryAmTheEggman

It is tricky, I still mess up all the time, and then bug Martin about it :D

Cᴏɴᴏʀ O'Bʀɪᴇɴ

where could I practice .NET regexes?

FryAmTheEggman

In retina? :P I think maybe regexhero or something was a site that let you run them...

Also could download mono

Martin Ender

here's a shorter idea: retina.tryitonline.net/… (still way too long though)

Cᴏɴᴏʀ O'Bʀɪᴇɴ

thanks, but I like not being sick

:P

Martin Ender

20:30

there's also regexstorm.net/tester which lets you inspect capturing groups

FryAmTheEggman

Ah right, that was the good one I think

Cᴏɴᴏʀ O'Bʀɪᴇɴ

this stuff is black magic ._.

Martin Ender

regexhero is pretty powerful actually, but I think it needs silverlight or something

FryAmTheEggman

Yeah it was just a pain to get working IIRC

Martin Ender

we should focus on that new challenge :P

FryAmTheEggman

20:33

The date one?

Martin Ender

yeah

FryAmTheEggman

Hmm, initial idea would be to do stuff like 01$ -> JAN but that seems bad

Martin Ender

now how to compress it... retina.tryitonline.net/…

Cᴏɴᴏʀ O'Bʀɪᴇɴ

weird idea, but maybe you could have : be a character like . and stand for ..

or is that not in the spirit of retina

(Obviously not just for this challenge)

FryAmTheEggman

I think the problem with that is that usually they will be like \w or something, so that would still be 2 bytes

Cᴏɴᴏʀ O'Bʀɪᴇɴ

20:38

oh

Martin Ender

@CᴏɴᴏʀO'Bʀɪᴇɴ hm yeah, seems a bit too much like microgolfing. I'd rather add features for common but cumbersome patterns (e.g. measuring the current horizontal position) or some that actually increase Retina's expressiveness

Cᴏɴᴏʀ O'Bʀɪᴇɴ

ah, good idea

I'm a microgolfer I guess :P

Martin Ender

@FryAmTheEggman well this golfing idea ended up at +/-0: retina.tryitonline.net/…

one byte shorter now retina.tryitonline.net/… ... this is unsatisfactory

this is somewhat better: retina.tryitonline.net/…

FryAmTheEggman

Haha, that's pretty cool!

Cᴏɴᴏʀ O'Bʀɪᴇɴ

indeed

Martin Ender

20:48

can save a byte with some linefeed abuse retina.tryitonline.net/…

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