1
00:00:00,520 --> 00:00:03,959
welcome everybody to another jam session

2
00:00:03,959 --> 00:00:08,360
where we're taking the I deres that we
developed

3
00:00:08,360 --> 00:00:11,780
and Haskell part of the course and show

4
00:00:11,780 --> 00:00:14,849
how we can use dan and other languages

5
00:00:14,849 --> 00:00:18,279
and that you may use at work and

6
00:00:18,279 --> 00:00:21,660
and that are not your functional
languages like ask

7
00:00:21,660 --> 00:00:24,869
and this time we're going to take a

8
00:00:24,869 --> 00:00:27,970
great look at scholar escolar

9
00:00:27,970 --> 00:00:32,369
is a and hybrid functional
object-oriented language

10
00:00:32,369 --> 00:00:35,620
it's not a pure language and it's in

11
00:00:35,620 --> 00:00:40,059
impaired language it has full side
effect ever runs on the JVM

12
00:00:40,059 --> 00:00:44,620
an and if you're a Haskell programmer

13
00:00:44,620 --> 00:00:48,379
you will feel very familiar with Scala
but also

14
00:00:48,379 --> 00:00:51,840
if you come from C sharp and you will
find

15
00:00:51,840 --> 00:00:58,379
that skyline and fits like a hand in
glove an

16
00:00:58,379 --> 00:01:01,930
to you and of course an for Java
programmers

17
00:01:01,930 --> 00:01:05,100
Scala also has a lot of benefits

18
00:01:05,100 --> 00:01:10,530
and in terms of conciseness that's a
look at this college

19
00:01:10,530 --> 00:01:13,909
cheat sheet to go through some of the
features

20
00:01:13,909 --> 00:01:20,150
and Scala has two kinds of

21
00:01:20,150 --> 00:01:23,450
parable decorations and you can define a

22
00:01:23,450 --> 00:01:26,509
far which means that you have immutable
variable

23
00:01:26,509 --> 00:01:30,049
or you can define a variable as FL

24
00:01:30,049 --> 00:01:35,850
which means that it's read only and and
so in that sense kala supports

25
00:01:35,850 --> 00:01:39,430
a.m. immutable and an values

26
00:01:39,430 --> 00:01:43,710
but this standard library has wide
variety

27
00:01:43,710 --> 00:01:48,960
of data structures including mutable
data types and immutable data that show

28
00:01:48,960 --> 00:01:51,170
its up to you as a developer

29
00:01:51,170 --> 00:01:55,119
to pick and choose rich gonna
programming

30
00:01:55,119 --> 00:01:59,140
an fits better so here

31
00:01:59,140 --> 00:02:02,340
are and Nikon I make this a little

32
00:02:02,340 --> 00:02:06,000
that an larger here's how you define

33
00:02:06,000 --> 00:02:09,000
am functions in skyline an

34
00:02:09,000 --> 00:02:11,650
you right def and then the function

35
00:02:11,650 --> 00:02:15,230
a name parameters and then the right
hand side

36
00:02:15,230 --> 00:02:18,860
and and Scala

37
00:02:18,860 --> 00:02:22,659
often can hanford to return died an

38
00:02:22,659 --> 00:02:26,629
and and in that case you know you have
to write

39
00:02:26,629 --> 00:02:29,920
equal show in this case this is a
function addiction and

40
00:02:29,920 --> 00:02:33,120
and returns X time six and inferred

41
00:02:33,120 --> 00:02:38,700
dive here return type is and we've seen

42
00:02:38,700 --> 00:02:43,200
an type synonyms and has gone and in
skyline E

43
00:02:43,200 --> 00:02:46,269
it even using the same syntax so you can
define

44
00:02:46,269 --> 00:02:49,840
type alias type re: was double here and
then

45
00:02:49,840 --> 00:02:54,069
wherever you used to use double and you
can use are

46
00:02:54,069 --> 00:02:57,650
here we see an example

47
00:02:57,650 --> 00:03:00,700
an and how make that

48
00:03:00,700 --> 00:03:04,310
even a little bit larger here for you
and

49
00:03:04,310 --> 00:03:07,930
here's an example often and on
instruction

50
00:03:07,930 --> 00:03:11,599
of /url on the expression you see the
Lund expression

51
00:03:11,599 --> 00:03:14,939
looks very much like ashkelon haskell
remembered us

52
00:03:14,939 --> 00:03:18,060
slash parameter single arrow

53
00:03:18,060 --> 00:03:21,680
expression escolar its an

54
00:03:21,680 --> 00:03:25,359
argument list wit types double arrow

55
00:03:25,359 --> 00:03:29,060
and then the body up the and expression

56
00:03:29,060 --> 00:03:35,500
we have seen several times in the
lectures and has gone that we're using

57
00:03:35,500 --> 00:03:36,400
the

58
00:03:36,400 --> 00:03:39,680
an range comprehension said you know

59
00:03:39,680 --> 00:03:43,159
square bracket 1.5 and Scala

60
00:03:43,159 --> 00:03:46,760
also support does and then set up dot
dot dot

61
00:03:46,760 --> 00:03:50,099
it uses to show if you're right 125

62
00:03:50,099 --> 00:03:56,440
and you get a sequence with the values
125 and of course

63
00:03:56,440 --> 00:04:00,139
scholarship board all their familiar
higher functions

64
00:04:00,139 --> 00:04:04,060
on those collections messages map and
filter

65
00:04:04,060 --> 00:04:07,989
and an re jus and so on so here for
example

66
00:04:07,989 --> 00:04:11,040
we see am mapping the

67
00:04:11,040 --> 00:04:14,269
function times to over the list

68
00:04:14,269 --> 00:04:17,409
and remember and has goal we used

69
00:04:17,409 --> 00:04:22,490
an sectioning an we were dry dysfunction

70
00:04:22,490 --> 00:04:24,910
as opened branch start to

71
00:04:24,910 --> 00:04:29,450
close Prenton and the skyline said using
sectioning with Brent sheesh

72
00:04:29,450 --> 00:04:33,330
you can use underscore so and you're
right underscore

73
00:04:33,330 --> 00:04:37,010
times too and which means to function
love the axe

74
00:04:37,010 --> 00:04:40,670
X times too and I must say often

75
00:04:40,670 --> 00:04:44,470
the underscore looks pretty nice because
you know it

76
00:04:44,470 --> 00:04:49,060
it gives very visual indication of where
the argument

77
00:04:49,060 --> 00:04:53,460
am is plugged in answer here you see for
example that embossing the

78
00:04:53,460 --> 00:04:56,490
operator plus as a function and then

79
00:04:56,490 --> 00:05:00,370
putting the two underscores their but of
course

80
00:05:00,370 --> 00:05:04,530
you can also and a ride it

81
00:05:04,530 --> 00:05:09,480
like this and and Scala an there's many
ways to ride the same thing to you can

82
00:05:09,480 --> 00:05:09,990
also

83
00:05:09,990 --> 00:05:13,640
ride take on section anything but II lie
I prefer

84
00:05:13,640 --> 00:05:17,870
this syntax alright

85
00:05:17,870 --> 00:05:24,870
so an where today the church's I want to
carry out a

86
00:05:25,860 --> 00:05:29,660
the go here and doubles

87
00:05:29,660 --> 00:05:33,070
an ass girl we used and doubles a lot

88
00:05:33,070 --> 00:05:36,590
an and the syntax of tuples

89
00:05:36,590 --> 00:05:40,120
in skyline is have very similar to
Haskell

90
00:05:40,120 --> 00:05:43,610
round brand to seize and develop use

91
00:05:43,610 --> 00:05:46,630
and just like in Haskell the types

92
00:05:46,630 --> 00:05:49,790
of the values in a couple can be
different

93
00:05:49,790 --> 00:05:54,280
and the lengths is part of the type and
that's what we see here

94
00:05:54,280 --> 00:05:58,050
they this thing here is doubled three

95
00:05:58,050 --> 00:06:01,990
and it has to retype parameters an

96
00:06:01,990 --> 00:06:06,750
you can do and a simple form of better
matching

97
00:06:06,750 --> 00:06:09,750
with double so I can count def the fine

98
00:06:09,750 --> 00:06:13,740
a at couple here on the left hand side
and it will bind

99
00:06:13,740 --> 00:06:16,890
in this case X tu wong white 22 and

100
00:06:16,890 --> 00:06:20,169
se23 and

101
00:06:20,169 --> 00:06:23,280
here's the an notation for

102
00:06:23,280 --> 00:06:26,570
that lists if I want to declare lest

103
00:06:26,570 --> 00:06:30,110
I ride to list 123 an

104
00:06:30,110 --> 00:06:33,550
and idiom and skyline is that you

105
00:06:33,550 --> 00:06:36,670
ish and factory classes

106
00:06:36,670 --> 00:06:41,010
an not list and that you don't write new

107
00:06:41,010 --> 00:06:44,390
so you define a class list and the you
define

108
00:06:44,390 --> 00:06:48,190
a corresponding and Object List and that
hasn't

109
00:06:48,190 --> 00:06:52,600
apply met that takes these parameters
and this apply matted

110
00:06:52,600 --> 00:06:55,870
is something that you don't ride and

111
00:06:55,870 --> 00:06:59,800
a year codes but that this column by the
roll call

112
00:06:59,800 --> 00:07:05,350
when you don't use a name for your mat
and Ghana has many more tricks like that

113
00:07:05,350 --> 00:07:08,640
and wit special Matt it's that

114
00:07:08,640 --> 00:07:12,460
has special meaning to define get their
chance at their San

115
00:07:12,460 --> 00:07:17,500
index there's an and strong an another
thing that I should mention is that

116
00:07:17,500 --> 00:07:20,250
Scala also supports extension methods

117
00:07:20,250 --> 00:07:24,850
just like C sharp and got then an so
when you have a class you can

118
00:07:24,850 --> 00:07:28,750
at and you matter to properties do that
class

119
00:07:28,750 --> 00:07:32,350
without having to touch the definition
of the class that something

120
00:07:32,350 --> 00:07:36,510
I like very much in that also
corresponds to the Haskell style very

121
00:07:36,510 --> 00:07:37,470
defined

122
00:07:37,470 --> 00:07:42,460
on your ads right data type there's no
matter it's the find their

123
00:07:42,460 --> 00:07:45,919
you define all their operations on those
dives

124
00:07:45,919 --> 00:07:50,950
separately the control structures in
Scala

125
00:07:50,950 --> 00:07:54,960
our standards and condition alls

126
00:07:54,960 --> 00:07:58,550
do while loops an foreign Lopes

127
00:07:58,550 --> 00:08:03,890
and scott also

128
00:08:03,890 --> 00:08:08,050
supports comprehension sis aint gonna
list branches that we have seen

129
00:08:08,050 --> 00:08:12,950
in Haskell an but it's got like they are
called for comprehension San

130
00:08:12,950 --> 00:08:17,350
maybe I should make this a little bit
smaller

131
00:08:17,350 --> 00:08:20,380
and and its doesn't look good

132
00:08:20,380 --> 00:08:23,940
I'm going to make bigger layout here's a
little bit messed up

133
00:08:23,940 --> 00:08:27,810
but here you see this would be to an has
call

134
00:08:27,810 --> 00:08:31,610
and list comprehension and

135
00:08:31,610 --> 00:08:34,940
it's called for calm branches and then
it uses the same

136
00:08:34,940 --> 00:08:41,719
left a road that we've seen haskell old
Eagle branches work

137
00:08:41,719 --> 00:08:46,430
an in Scala you can do pattern matching
as well with the k-state

138
00:08:46,430 --> 00:08:49,990
and so an you can define your own

139
00:08:49,990 --> 00:08:54,290
and and apply Matt it's on an object

140
00:08:54,290 --> 00:08:57,390
and then you can use that to do better
matching so it's its kinda

141
00:08:57,390 --> 00:09:00,950
nicer are more powerful pattern matching
even

142
00:09:00,950 --> 00:09:04,110
then asked began as going again only
better match

143
00:09:04,110 --> 00:09:08,270
on the constructors open algebra
datatype and in Scotland

144
00:09:08,270 --> 00:09:12,860
and you can tweak that colleges

145
00:09:12,860 --> 00:09:16,230
rather big language and

146
00:09:16,230 --> 00:09:19,870
it as implicit parameter that

147
00:09:19,870 --> 00:09:25,510
an gonna factor out to the idea of
Haskell type classes in high school

148
00:09:25,510 --> 00:09:28,700
we have a typed last year when you see
the am

149
00:09:28,700 --> 00:09:32,620
type constraint on the left Ave type
with a double arrow

150
00:09:32,620 --> 00:09:38,190
the Hesco compiler will threats through
and an instance of that type class

151
00:09:38,190 --> 00:09:41,620
as an implicit parameter and whenever
you call that netted

152
00:09:41,620 --> 00:09:44,950
ordered that function it will come to
propagate

153
00:09:44,950 --> 00:09:48,029
that implicit parameter an but you
cannot

154
00:09:48,029 --> 00:09:51,080
used this concept implicit parameters

155
00:09:51,080 --> 00:09:55,140
separate from type classes now there are
haskell extensions

156
00:09:55,140 --> 00:09:58,459
and that allow for implicit parameters

157
00:09:58,459 --> 00:10:01,560
an and Scott to this I'm

158
00:10:01,560 --> 00:10:06,900
a lot for order an and there's many many
library functions

159
00:10:06,900 --> 00:10:10,110
that use implicit parameters an

160
00:10:10,110 --> 00:10:13,610
in a very powerful way and you can use
that to yourself

161
00:10:13,610 --> 00:10:17,890
okay to an of an looking at the cheat
sheets

162
00:10:17,890 --> 00:10:21,330
let's finish by showing some scholar
college

163
00:10:21,330 --> 00:10:25,170
and where do we go I wanted

164
00:10:25,170 --> 00:10:32,170
go to mine Scotland I'll here

165
00:10:34,019 --> 00:10:36,230
make this a bit larger for you

166
00:10:36,230 --> 00:10:39,820
and I'm using the same

167
00:10:39,820 --> 00:10:43,940
a more or less the same example as I did
before sure there's the main method

168
00:10:43,940 --> 00:10:47,680
I print lol I define a local function I
define

169
00:10:47,680 --> 00:10:51,730
wise I print itself and here I'm
defining

170
00:10:51,730 --> 00:10:54,950
a local function that closes over

171
00:10:54,950 --> 00:10:58,209
immutable state and mutates that
terrible

172
00:10:58,209 --> 00:11:02,060
inside here too easy there's the

173
00:11:02,060 --> 00:11:05,430
mutable variable Z and I muted inside
here

174
00:11:05,430 --> 00:11:10,560
goal this thing twice should the second
time

175
00:11:10,560 --> 00:11:15,730
and she will be forty and then will be
mutated again so that's run this code

176
00:11:15,730 --> 00:11:19,370
to see if everything works at advertised

177
00:11:19,370 --> 00:11:24,200
and hello for and you see here that when
I call mutate

178
00:11:24,200 --> 00:11:27,250
twice the first time it brings 40

179
00:11:27,250 --> 00:11:30,370
and the second time branch 15 so

180
00:11:30,370 --> 00:11:33,870
you date is not a at your function

181
00:11:33,870 --> 00:11:38,339
and let's am

182
00:11:38,339 --> 00:11:41,850
at the explicit type definition so

183
00:11:41,850 --> 00:11:46,380
what we see here said you date is a
function that takes no arguments and

184
00:11:46,380 --> 00:11:47,430
returns and

185
00:11:47,430 --> 00:11:50,810
but it's not a mathematical your
function

186
00:11:50,810 --> 00:11:55,010
because if I call it twice it will give
me a different result

187
00:11:55,010 --> 00:11:58,190
but sometimes that is useful

188
00:11:58,190 --> 00:12:01,360
alright so I hope that you a.m. enjoyed

189
00:12:01,360 --> 00:12:04,829
a.m. this little overview of Scala an

190
00:12:04,829 --> 00:12:09,350
and if you're on the JVM I would
definitely consider

191
00:12:09,350 --> 00:12:12,899
skyline as a great language to apply

192
00:12:12,899 --> 00:12:16,500
the functional programming techniques
that we learned in this course see you

193
00:12:16,500 --> 00:12:16,850
next time