watching fun fun function if you are a
regular viewer of the show you can might
notice that this is not my normal voice
ah that is because I have been partying
and screaming for the last three days
which I am actually way too old to do so
today is like what better day to tackle
one of the more complicated programming
languages in the world
let’s start doing your high school
course yeah let’s do that
so then why should we learn Haskell to
be perfectly honest with you I don’t
know entirely why because I don’t know
Haskell so we will be learning it
together on this course functional
programming has been growing wildly in
the last few years my series on
functional programming in JavaScript is
way more popular than I thought it would
be I think the movement really picked up
speed when Facebook launched react I
think that’s when functional programming
really started hitting mainstream
programming recently a lot of people
have started using a react together with
a library called redux which is an
amazing library it allows you to express
your UI logic in a very very functional
manner and makes it really easy to
reason about if you’re not using Redux
and you’re using react you’re basically
living your life wrong you should check
out this tutorial by wes boss on redux
it is amazing so to me Haskell has
always seen like there’s some almost
mythical beast of a programming language
whenever you look at it it looks like
nothing else it’s not a very popular
language however at the same time are
the people that do work with it seem to
really really like it if you look at the
Stack Overflow survey of 2016 it is one
of the most loved programming languages
and what I mean by that is that they
they asked the people what they work
with and the percentage of people
that expressed interest in continuing to
work with that also a lot of very smart
people around me of our advocates of of
Haskell and also a lot of people like
celebrities that I look up to like John
Carmack also speak very highly of
Haskell so it seems to me like it can’t
be too badly spent time to explore
Haskin see what what it’s all about so
as I said I don’t know Haskell so we
need some kind of learning resource here
and for our curriculum I have picked
learn you a Haskell for great good it’s
a free online book you can read it
online for free and you can also buy it
if you want to give money to find people
I have picked this book up primarily
because it has a very funny title and it
also has a son saying holy okay
let’s get started
reading online I’ll learn you a Haskell
for great good all right introduction
about this tutorial so what’s Haskell
what do you need to dive in starting out
ready set go
awesome click that ready set go
alright let’s get started if you’re in
sort of horrible person who doesn’t read
instructions to things and you skipped
it you might want to read no I ah like
the first thing yeah okay so they want
you to install the Haskell compiler you
probably already have that install
because you have tried to learn Haskell
once and then failed ah but if you don’t
uh it you just google Haskell download
and click things until it’s installed
but once you have it you write gay DG
c-h-i and that sounds for great compiler
Haskell are interactive oh it’s great
Haskell compiler interactor right so
they say that you can set the prompt to
gch i ah here I not sure why would you
would
do that because like you are you want to
set that to an emoji I think emoji ah
get list of all emojis copy and paste
let’s find one
what picking an emoji for your hashcode
terminal eyes it’s very easy to get
stuck here as you see now I’m stuck
trying to decide on an emoji oh yeah
these this this is this is possibly the
weirdest emoji in once you have
completed that step we can start
learning Haskell the Haskell is here so
I can type 2.15 1749 times 100 and and
it makes Matt and I can do 5/2 and it
divides it and it’s also yes like
JavaScript in this you can just write
you know math like for 9.99
and you can yeah it calculates it it
also warns about this caveat like if you
you’re using negative numbers like 50
times – what you can’t do that ah that’s
pretty weird also the error here like
this is horrible
uh but either way you need to do
parentheses around – once as a
JavaScript programmer that makes me
kinda happy because people nag about the
pitfalls of JavaScript all the time but
at least JavaScript doesn’t have this
and you can do boolean expressions
like true and false
that’s equals false you know like we’ll
see you can did you do true and false no
true – of course yeah it’s gonna be true
I guess yes and you can also do the or
or operators like yes or false you can
also negate things so not false becomes
true this is like writing this in in
JavaScript and you can infer
qualities of five equals five is true
and five equals four that’s false you
can also check that five is is not equal
to so five is it’s not equal to 4 that
is is true and if you do 5 is not equals
to 5 that is false
double negation um the equivalent on
this in JavaScript would be this right
so what if we try 5 plus hello okay so
it says that no instance of namche are
arising from use of plus in the
expression 5 plus hello in an equation
for it it equals 5 plus hello this is
quite possibly the worst error message
ever devised
but what it’s trying to say is that it
Haskell doesn’t know how to add aa 5 and
hello together because 5 is a 5 is a
number and hello is a string in
JavaScript this had would just have
ended up being a hello and that is
because JavaScript does something called
type coercion it just tries to when it
when it sees something like with this
when JavaScript sees something like this
it just tries to like coerce the two
things into a general type that can be
added together and it squashes them
together which can sometimes be helpful
and sometimes not you know I’m not sure
if I think it’s a good idea or a bad
idea but JavaScript does that ah and
Haskell absolutely no it’s not Haskell
is very picky about the types and it
uses this a lot to try to assist you in
writing correct programs so Plus here in
Haskell it expects both sides to be
numbers I’m not sure if you can can you
plus two strings to get like hello plus
well now you can’t but I could perhaps I
can do this
yes I can so if I hello yeah I can so
equals works on on strings and numbers
but plus only works on numbers however
if I do this hello is not equals of five
it breaks with an error message from the
moon oh but but that is actually because
I’m trying to write JavaScript in
Haskell which does not work no it’s it’s
this one hello and we can try that
compare that to five it’s still a very
hard to understand error message but
what it’s trying to say is that not
equals to five can only compare a things
things of the same type Haskell very
picky about types you can do five plus
four plus one I think yeah that actually
confuses me because it feels a little
bit inconsistent because in my world
this is an int and this is a float uh
and I still think they are in Haskell
but they I guess it did it says that
four can act like an integer but two
five is one that has to adapt I don’t
know it’s confusing you may not have
known it but we’ve been using functions
now all along what okay that means that
plus is actually a function and this is
a function and if I type five five if I
type five times five and that becomes
like this is actually a function and
functions in Haskell that our sandwich
in between like this they are called
in fix functions but most functions that
deal with are non numbers they are
called
fix functions and they are they are more
like what we were used to in JavaScript
so let’s take a look at them
we’ll start by learning the most boring
function Haskell with it which is suck
and suck works like you press right give
it six and then it calls seven and if
you lose sex like a gives you nine what
zero all right
in JavaScript the equivalent syntax
would would just be uh like six but in
Haskell less as you see a castle is
extremely concise it has just much
syntax as you need but no more another
function in Haskell is minimum I mean
like so if I say sex seven it’s going to
give me sex works like I guess there is
a max maybe max yeah so we can combine
this and say min six seven and then add
max six ten thousand and that will give
us ten thousand six so the order
execution of these things are not
obvious but it it function application
which is what has scholars refer to it’s
this thing is when you write a function
and then you add a space and then
arguments that will have precedence over
in fix application like this which means
that it will first execute the min six
seven and then max six ten thousand and
then it will plus them together thus
giving us the right answer however if we
write suck nine times ten that will be
wrong because suck nine will win over a
time stand here like so it will is going
to do suck nine which will be 10 and
then it will multiply that with
and if we want to make sure that this
yeah like that so adding parentheses
works just like in math it just means
that we execute this first before
passing to the function here so this is
one of the things that strikes me with
Haskell if it feels a bit more mathy
than JavaScript does unfortunately this
also means that a lot of examples refer
to math so in in this in the book here
it says that for instance that Dib
functions take two integers and does
integral division between them if you
don’t know what integral division is ah
that’s you’re not alone I don’t know
either
I guess it divides it and throws away
house call this is why nobody uses you
screw that that’s not even what the
author of the book is trying to explain
what they are trying to explain is that
you can apply functions prefix functions
like in fix functions by adding
backticks to them so I can do 92 Dave ah
and AH 10 no that didn’t work
I don’t know backticks backticks that’s
it so I can do that this this statement
here is the same as this one because I
added added backticks here so I guess I
can do this with with Mac’s as well or
something yeah so this is one of the
things that makes haskell look a bit
weird because yeah in in JavaScript uh
all these functions would look something
like something like this right but like
they have up parentheses here and they
have a comma to separate the arguments
but in Haskell it’s much more terse and
looks like that if you see something
like this that’s a bad example normally
like this then that just means that uh
yeah this is evaluated first this has no
real significance in this this thing we
we can just do 92 by the way if I do
suck suck 92 from that give us our 94 no
it won’t I guess I need to add
parentheses yes
so yeah it’s Maddy that’s it for today
you did good we got our feet a little
bit wet with the
the basics of Haskell syntax and next
time we’re gonna look at how to declare
our own functions I’ve linked to the
chapter in learn your Haskell down below
you have just watched an episode of fun
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miss out on the next episode I mmm PJ until next Monday morning stay curious