text stringlengths 1 81 | start float64 0 10.1k | duration float64 0 24.9 |
|---|---|---|
zero or more which gives you all the | 3,989.52 | 5.599 |
flexibility in the world yeah so I was | 3,991.92 | 5.76 |
just asking that uh uh with question | 3,995.119 | 5.601 |
mark there's only one repetition allow | 3,997.68 | 5.28 |
it means zero or one repetition so it's | 4,000.72 | 5.599 |
either not there or it is there and so | 4,002.96 | 5.319 |
that's why this pattern now if I go back | 4,006.319 | 3.641 |
to my code even though again it | 4,008.279 | 3.721 |
admittedly looks cryptic let me | 4,009.96 | 4.56 |
highlight everything after the at sign | 4,012 | 5.079 |
and before the dollar sign sign this now | 4,014.52 | 4.88 |
represents a domain name like | 4,017.079 | 5.96 |
harvard.edu or a subdomain within the | 4,019.4 | 6.32 |
domain name why well this part to the | 4,023.039 | 5.721 |
right is the same as always backw plus | 4,025.72 | 5.92 |
means something like Harvard or Yale | 4,028.76 | 6.48 |
back.edu means literally doedu so the | 4,031.64 | 6.24 |
new part is this in parentheses I have | 4,035.24 | 7.119 |
another set of backw plus back SL do now | 4,037.88 | 6.88 |
but it's all in parentheses I'm now | 4,042.359 | 4.281 |
having any question mark right after | 4,044.76 | 3.44 |
that which means that whole thing in | 4,046.64 | 4.52 |
parentheses either can be there or it | 4,048.2 | 4.72 |
can't be there it's either of those that | 4,051.16 | 4.48 |
are acceptable so a question mark | 4,052.92 | 5.24 |
effectively makes something optional it | 4,055.64 | 4.24 |
would not be correct to remove the | 4,058.16 | 3.919 |
parentheses because what would this mean | 4,059.88 | 4.479 |
if I remove the parentheses that would | 4,062.079 | 5.401 |
mean that only this dot is optional | 4,064.359 | 4.48 |
which isn't really what we want to | 4,067.48 | 5.16 |
express I want the subdomain like cs50 | 4,068.839 | 5.921 |
and the additional dot to be what's | 4,072.64 | 3.919 |
there or not there there how about one | 4,074.76 | 4.88 |
other question on rexus here can they | 4,076.559 | 6.04 |
use this for the usernames absolutely we | 4,079.64 | 4.399 |
still have other problems right we're | 4,082.599 | 3.081 |
not solving all of the problems today | 4,084.039 | 4.28 |
just yet but absolutely right now we are | 4,085.68 | 5 |
not letting you have a period in your | 4,088.319 | 3.96 |
username and again some of you with | 4,090.68 | 3.599 |
Gmail accounts or other accounts you | 4,092.279 | 3.441 |
probably have not just underscores | 4,094.279 | 2.56 |
numbers and letters you might have | 4,095.72 | 4.079 |
periods too well we could fix that not | 4,096.839 | 5.241 |
using question mark here per se but now | 4,099.799 | 4 |
that we have these parentheses at our | 4,102.08 | 4.84 |
disposal what I could do is this I could | 4,103.799 | 6.56 |
use parentheses to surround the back slw | 4,106.92 | 5.16 |
to say any word character which is the | 4,110.359 | 4.081 |
same thing again as a letter or a number | 4,112.08 | 5.159 |
or an underscore but I could also or in | 4,114.44 | 6.04 |
using a vertical bar something else like | 4,117.239 | 6 |
a literal dot now a literal dot needs to | 4,120.48 | 4.96 |
be escaped otherwise it represents any | 4,123.239 | 3.881 |
character which would be a regression a | 4,125.44 | 4.08 |
step back but now notice what I've done | 4,127.12 | 5.639 |
in parentheses I'm telling re. search | 4,129.52 | 5.239 |
that those first few characters in your | 4,132.759 | 4.161 |
email address that is your username has | 4,134.759 | 5.361 |
to be a word character Like A through Z | 4,136.92 | 5.56 |
uppercase or lowercase or 0 through 9 or | 4,140.12 | 5.599 |
an underscore or a literal dot we could | 4,142.48 | 5.04 |
do this differently too I could get rid | 4,145.719 | 4.361 |
of the parentheses and the or and I | 4,147.52 | 4.56 |
could just use a set of characters I | 4,150.08 | 5.119 |
could again manually say a through z a | 4,152.08 | 7.079 |
through z 0 through 9 underscore and | 4,155.199 | 5.921 |
then I could do a literal dot with a | 4,159.159 | 4.56 |
back slash period and now I technically | 4,161.12 | 4.039 |
don't even need the uppercase because | 4,163.719 | 2.921 |
I'm already telling the computer to | 4,165.159 | 3.52 |
ignore case I can just pick one or the | 4,166.64 | 4.119 |
other which one is better is really up | 4,168.679 | 3.48 |
to you whichever one you think is more | 4,170.759 | 3.92 |
readable would generally be the better | 4,172.159 | 5.361 |
design all right let me propose that I | 4,174.679 | 6.321 |
rewind this in time to where we left off | 4,177.52 | 6.52 |
which was here and let me propose that | 4,181 | 5 |
there are indeed still limitations of | 4,184.04 | 4.52 |
this solution not just with the username | 4,186 | 3.92 |
not just with the domain name we're | 4,188.56 | 3.52 |
still being a little too restrictive so | 4,189.92 | 4 |
would you like to see the official | 4,192.08 | 3.32 |
regular expression that at least | 4,193.92 | 3.84 |
browsers use nowadays whenever you type | 4,195.4 | 4.24 |
in an email address to a web form and | 4,197.76 | 4.479 |
the web form the browser tells you yes | 4,199.64 | 4.24 |
or no your email address is | 4,202.239 | 6.48 |
syntactically valid ready ready here is | 4,203.88 | 7.839 |
and this isn't even officially the right | 4,208.719 | 5.121 |
regular expression it's a simplified | 4,211.719 | 3.921 |
version that browsers use because it | 4,213.84 | 4.44 |
catches most mistakes but not all here | 4,215.64 | 6.44 |
we go this is the regular expression for | 4,218.28 | 6.48 |
a valid email address at least as | 4,222.08 | 5.84 |
browsers nowadays Implement them now | 4,224.76 | 6.24 |
it's crazy cryptic at first glance but | 4,227.92 | 5.2 |
not and it's wrapping onto many lines | 4,231 | 4.48 |
but it's just one pattern but just | 4,233.12 | 5.32 |
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