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00:00:00,040 --> 00:00:02,880
This will be an overview
of the syntax.

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00:00:03,040 --> 00:00:06,240
We'll show you
the entirety of the syntax...

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00:00:06,400 --> 00:00:09,440
Don't get stressed
if you don't understand it completely.

4
00:00:09,600 --> 00:00:11,400
We'll go over it all again.

5
00:00:11,560 --> 00:00:15,360
The idea is to show you
all there is in Pharo.

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00:00:16,040 --> 00:00:20,000
We're going to look
at the main syntactical elements.

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00:00:20,160 --> 00:00:22,760
We'll see that there are
3 kinds of messages.

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00:00:22,920 --> 00:00:25,280
And well look at block syntax,

9
00:00:25,440 --> 00:00:27,440
an essential part of Pharo.

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00:00:27,600 --> 00:00:32,000
Don't worry if you don't get it all,
we'll repeat all the points.

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00:00:33,120 --> 00:00:37,320
Just to remind you,
you have all the syntax on this slide.

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00:00:37,480 --> 00:00:40,040
I can go into the details a bit now.

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00:00:40,200 --> 00:00:43,960
Here's a method definition,
exampleWithNumber.

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00:00:44,120 --> 00:00:46,120
And it has an argument.

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I have local variable definitions
with vertical bars.

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I have the return,
which lets me give a value.

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I have loops, an affectation...

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The period, for example,
is an instruction separator.

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We'll look at all this.

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We'll start
with the traditional Hello World.

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Here, if you like...

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00:01:12,160 --> 00:01:16,400
You can execute all instructions
in Pharo yourself

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00:01:16,560 --> 00:01:18,360
to see what the result is.

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So here I have a string,

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which I convert into a morph,
a graphic element,

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and I ask it
to open in a window.

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So I send asMorph
to the string object.

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And I send openInWindow

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to the resulting morph.

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So we have two message sends
and one string object.

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A more complicated example.

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00:01:44,120 --> 00:01:47,920
Imagine you want to take
the Pharo logo from the web.

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00:01:48,280 --> 00:01:50,800
Well, you do it this way.

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You do ZnEasy getPng:
with a string which represents the URL

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00:01:57,000 --> 00:02:00,000
of the resource you want to read.

36
00:02:00,160 --> 00:02:04,440
And once again you convert it
into a graphic object

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and ask it to open in a window.

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So we see that ZnEasy is a class

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because classes start with a capital.

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The colon of the message getPng:
means I'm expecting an argument,

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00:02:17,960 --> 00:02:22,120
which is the string
http://pharo.org.

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This string is the argument
of the method getPng:

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00:02:28,280 --> 00:02:32,520
The messages asMorph
and openInWindow

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are read from left to right.

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So you can cut'n'paste this code

46
00:02:38,800 --> 00:02:41,000
or retype it in Pharo,

47
00:02:41,160 --> 00:02:43,760
and you'll get the Pharo logo.

48
00:02:43,920 --> 00:02:47,200
So what syntactical elements
are there in Pharo?

49
00:02:47,360 --> 00:02:50,680
You have comments, which start
with double quotation marks.

50
00:02:50,840 --> 00:02:52,200
That's a comment.

51
00:02:52,360 --> 00:02:55,840
Characters are always preceded
by a dollar sign.

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$A is the character A.

53
00:02:58,240 --> 00:03:02,280
Strings start and finish
with a single quotation mark.

54
00:03:03,400 --> 00:03:05,920
You have symbols,
which are unique strings.

55
00:03:06,080 --> 00:03:10,320
These begin like this,
with the hashtag.

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00:03:10,480 --> 00:03:12,840
#a is the symbol a.

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There are literal arrays.

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Here I have one with 12, 23 and 36.
Three elements.

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Integers have various representations,

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00:03:22,440 --> 00:03:24,600
but we won't dwell on this.

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We usually use representations
in base 10.

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But if you want one in base 2,
that's OK.

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You have reals.
This is the same.

64
00:03:32,920 --> 00:03:35,200
You can find the syntax if you need.

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You have booleans,
with true and false.

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You have undefined.

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00:03:39,960 --> 00:03:43,640
The null of Java is nil in Pharo.

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It's an instance
of the class UndefinedObject.

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And you have points.

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00:03:49,480 --> 00:03:52,720
This is described in Pharo
under the form

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00:03:52,880 --> 00:03:56,440
of 10 @ 200, for example.

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So I'm creating the point 10,
which is 10 on the x,

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and 200 on the y.

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00:04:03,680 --> 00:04:07,040
So we've seen the essential elements
for the syntax.

75
00:04:07,200 --> 00:04:09,840
Now we have the constructs
of the language.

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You have
temporary variable declaration.

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It's a vertical bar
followed by another vertical bar.

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00:04:16,360 --> 00:04:19,320
Assignment
is a colon and an equal sign.

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00:04:19,480 --> 00:04:22,520
In the variable var I put aValue.

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00:04:22,720 --> 00:04:24,640
I have messages in my system.

81
00:04:24,800 --> 00:04:26,280
How do I separate them?

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00:04:26,440 --> 00:04:28,240
With a period.

83
00:04:28,400 --> 00:04:30,760
When I want a sequence of messages.

84
00:04:30,920 --> 00:04:32,000
There's return,

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00:04:32,160 --> 00:04:34,560
where a function or method
gives a value.

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00:04:34,720 --> 00:04:39,520
I use the little hat,
which is called caret in English.

87
00:04:39,680 --> 00:04:41,200
Then you have blocks,

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which, technically speaking,
are lexical closures,

89
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and which you can take
as anonymous methods.

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I'll show you what a block is.

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It's defined with square brackets.

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And it's executed
with the message value.

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We'll look at this.

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00:05:01,320 --> 00:05:03,960
There you have all the constructs.

95
00:05:05,240 --> 00:05:08,520
So what is the essence
of a Pharo program?

96
00:05:08,680 --> 00:05:12,240
It's creating objects
by using messages,

97
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sending messages to these objects,

98
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and, now and then,
using blocks, or anonymous methods.

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That's all.

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There are three types
of message in Pharo. Why?

101
00:05:23,240 --> 00:05:26,560
In order to minimize
the number of parentheses used.

102
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It's fairly simple.

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00:05:28,480 --> 00:05:32,360
A unary message
is always a receiver and a selector.

104
00:05:32,520 --> 00:05:35,480
Here for example I've said
that I want 9 squared.

105
00:05:35,640 --> 00:05:37,680
I want today's date.

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I send the message today
to the class Date.

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00:05:41,960 --> 00:05:43,800
There's no argument.

108
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Then there's the binary message,

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which also takes the form
of a receiver, selector and argument.

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00:05:51,160 --> 00:05:52,640
But the selector will be

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00:05:52,800 --> 00:05:57,320
plus, minus, tilde, equals, slash...
That sort of thing.

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00:05:57,480 --> 00:06:01,080
All those mathematical signs
are for binary messages.

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00:06:01,360 --> 00:06:04,560
Here we see 1+2.
This is a message.

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00:06:04,720 --> 00:06:08,080
Sending message + to object 1
with argument object 2.

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00:06:08,240 --> 00:06:11,240
@ for the creation of a point
is also a message,

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a binary message.

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00:06:12,920 --> 00:06:16,160
Here I create the point 3@4

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by sending the message @.

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00:06:18,800 --> 00:06:22,200
Then you have
what we call keyword messages.

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A keyword message takes the form

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of receiver key1: arg1 key2: arg2.

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00:06:29,000 --> 00:06:31,440
So the example is...

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00:06:31,600 --> 00:06:34,720
is 2 between 10 and 20

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00:06:35,000 --> 00:06:38,760
If you wrote it in Java or C
it would be like this...

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00:06:39,000 --> 00:06:44,320
You'd write betweenAnd...

126
00:06:44,480 --> 00:06:48,920
Then, between brackets,
you'd write (10, 20).

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00:06:49,080 --> 00:06:53,720
In Pharo you express it
in the form of key and key.

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00:06:53,880 --> 00:06:57,520
We'll look at this again, but it gives
you an idea of the syntax.

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00:06:58,800 --> 00:07:02,680
There's a precedence
between messages,

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00:07:02,840 --> 00:07:06,480
the system will execute in priority
the parentheses,

131
00:07:06,640 --> 00:07:09,200
then the unary,
binary and keyword messages.

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00:07:09,360 --> 00:07:10,160
Why?

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To avoid writing too many parentheses.

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00:07:13,720 --> 00:07:17,880
We could have had a system
with parentheses all over the place,

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but the code would be illegible.

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I'll go back over each type of message
in a simple way.

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This unary message, 10000 factorial.

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00:07:27,840 --> 00:07:30,160
Try it, it's a very big number.

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00:07:30,320 --> 00:07:33,640
I send the message factorial
to the object 10000.

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00:07:33,800 --> 00:07:36,240
There's no argument,
it's a unary message.

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00:07:36,880 --> 00:07:41,840
Similarly, a binary message.
1+3 is a message, a binary message.

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00:07:42,000 --> 00:07:46,720
The selector,
the name of the method, is +.

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00:07:47,360 --> 00:07:52,040
I send the message + to the object 1
with the object 3 as argument.

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00:07:53,120 --> 00:07:55,960
A keyword message,
as I explained earlier...

145
00:07:56,120 --> 00:08:00,360
I'll just tell you again.
Teaching is all about repetition.

146
00:08:00,800 --> 00:08:04,520
I have a keyword message
with keyword and keyword,

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00:08:04,680 --> 00:08:07,560
which is the message,
with the arguments,

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00:08:07,720 --> 00:08:11,080
which are floating inside the message.

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00:08:11,240 --> 00:08:14,680
The idea is to have a syntax
that children can use

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00:08:14,840 --> 00:08:18,320
and to have something
close to English.

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00:08:18,480 --> 00:08:24,280
So you can introduce the arguments
inside your messages.

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00:08:25,440 --> 00:08:29,120
As an example, imagine
I'm sending an HTTP request.

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00:08:29,280 --> 00:08:32,880
ZnClient is a Pharo HTTP server.

154
00:08:33,040 --> 00:08:35,880
So I create an instance of Zn server.

155
00:08:36,040 --> 00:08:40,680
So new is a unary message,
there's no argument, no colon.

156
00:08:41,560 --> 00:08:46,720
url is a keyword message,
there's a colon.

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00:08:46,880 --> 00:08:49,880
queryAt: put:
is another message.

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00:08:50,040 --> 00:08:52,600
It's another keyword message.

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00:08:52,760 --> 00:08:54,880
And get is a unary message.

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00:08:55,360 --> 00:08:59,400
What we can also see
in this example are semi-colons.

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00:08:59,760 --> 00:09:02,120
We call this a cascade,

162
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which sends all the messages
to the same object.

163
00:09:05,960 --> 00:09:08,920
You don't need
a temporary variable.

164
00:09:09,080 --> 00:09:12,320
And you can write more compact code.

165
00:09:13,720 --> 00:09:17,080
You have to understand
that messages are everywhere.

166
00:09:17,240 --> 00:09:20,880
Conditionals, loops, iterators and
concurrency are expressed as messages.

167
00:09:21,040 --> 00:09:23,480
My explanation
about those three messages

168
00:09:23,640 --> 00:09:25,560
applies across the board.

169
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It's the cornerstone of the system.

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00:09:27,920 --> 00:09:31,000
There's nothing other
than these messages.

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00:09:31,520 --> 00:09:32,880
Let's have a look.

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00:09:33,040 --> 00:09:35,520
I've taken
the silly factorial definition here.

173
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How do I define it?

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I define my method factorial.

175
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I put a comment for the method.
Double quotation marks.

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And I start with self.

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If the object
getting the message is zero,

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then I'll give 1.

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If self is positive,

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00:09:51,480 --> 00:09:55,160
for example, factorial 6,
self equals 6...

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00:09:55,480 --> 00:09:58,120
If this is true
than what will I give?

182
00:09:58,280 --> 00:10:01,520
6 multiplied by 6 minus 1 factorial.

183
00:10:01,680 --> 00:10:04,920
The recursive definition we all know.
And that's that.

184
00:10:05,080 --> 00:10:08,120
And the interesting thing to note here

185
00:10:08,280 --> 00:10:10,440
is that ifTrue:, which is a condition,

186
00:10:10,600 --> 00:10:13,720
is also a message,
a keyword message with a colon,

187
00:10:13,880 --> 00:10:15,320
sent to a boolean.

188
00:10:15,480 --> 00:10:18,800
You also have ifFalse:ifTrue:,
ifTrue:ifFalse:...

189
00:10:18,960 --> 00:10:21,440
All these conditions are messages

190
00:10:21,600 --> 00:10:23,320
which satisfy the rules,

191
00:10:23,480 --> 00:10:28,680
and are keyword messages
like I presented earlier.

192
00:10:29,080 --> 00:10:30,960
So conditions are messages.

193
00:10:31,120 --> 00:10:32,960
Loops are messages too.

194
00:10:33,120 --> 00:10:35,160
Here I'll make a loop from 1 to 4.

195
00:10:35,320 --> 00:10:37,840
From 1 to 4, what do I do?

196
00:10:38,000 --> 00:10:40,080
A block.
An anonymous method.

197
00:10:40,240 --> 00:10:45,360
Here I'm saying I want it
to show the value of i,

198
00:10:45,520 --> 00:10:50,320
and i will take the value
of 1, 2, 3, 4...

199
00:10:50,480 --> 00:10:53,840
And there you can see that to: do:

200
00:10:54,000 --> 00:10:56,280
is a keyword message.

201
00:10:56,520 --> 00:10:59,960
It's a message
that takes the form of a loop.

202
00:11:00,120 --> 00:11:03,360
There are other loops in Pharo:
timesRepeat:, to:by:do: and so on.

203
00:11:03,520 --> 00:11:05,360
We'll look at them all.

204
00:11:05,520 --> 00:11:07,520
But, again, these are messages...

205
00:11:07,680 --> 00:11:11,440
So here, to: do: is sent to object 1
with 4 as parameter and a block.

206
00:11:11,600 --> 00:11:14,600
We'll see what a block is very soon.

207
00:11:14,760 --> 00:11:16,480
You also have iterators.

208
00:11:16,640 --> 00:11:18,440
Iterators are different.

209
00:11:18,600 --> 00:11:21,040
I send the message do:

210
00:11:21,200 --> 00:11:22,360
to the collection,

211
00:11:22,520 --> 00:11:25,680
saying what I want to apply
to each of the elements.

212
00:11:25,840 --> 00:11:29,320
So the each,
the argument of my function,

213
00:11:29,480 --> 00:11:34,440
will take as value
1, 2, -4 and -86.

214
00:11:34,600 --> 00:11:36,960
And what I do here
is that the each...

215
00:11:38,440 --> 00:11:40,800
I apply the absolute value
and display it.

216
00:11:40,960 --> 00:11:43,840
Once again,
this will be another course.

217
00:11:44,000 --> 00:11:45,720
We'll explain iterators.

218
00:11:45,880 --> 00:11:48,640
Iterators are something
you get in Java 8.

219
00:11:50,280 --> 00:11:53,240
And they're part of the core of Pharo.

220
00:11:54,280 --> 00:11:55,760
So what is a block?

221
00:11:55,920 --> 00:11:57,680
Blocks look like functions.

222
00:11:57,840 --> 00:12:01,320
If in maths you wrote f(x) = x²+3,

223
00:12:01,480 --> 00:12:03,920
you'd write it like this, literally.

224
00:12:04,440 --> 00:12:07,320
I define a variable
in which I affect a block.

225
00:12:07,480 --> 00:12:10,520
A block is something
inside square brackets.

226
00:12:10,680 --> 00:12:13,160
Here, the block has an argument
which is x.

227
00:12:13,520 --> 00:12:16,640
And I put a core, which is x+3.

228
00:12:16,800 --> 00:12:18,600
And when I want
to execute this block...

229
00:12:18,760 --> 00:12:20,880
The application of the function.

230
00:12:21,040 --> 00:12:24,600
That's the definition of the function,
now I have the application.

231
00:12:24,760 --> 00:12:30,360
I send the message value:
to the block. I put value: 2.

232
00:12:31,520 --> 00:12:35,080
x is 2,
so my block will give me 5.

233
00:12:35,520 --> 00:12:36,680
OK?

234
00:12:36,960 --> 00:12:41,560
So what's a block? It's a kind
of anonymous function, it has no name.

235
00:12:41,960 --> 00:12:46,160
In fact, it's a lexical closure.

236
00:12:46,320 --> 00:12:48,240
We'll explain that.

237
00:12:48,400 --> 00:12:50,360
Blocks are real objects.

238
00:12:50,520 --> 00:12:54,440
They can be passed as method
arguments, stored in variables,

239
00:12:54,600 --> 00:12:55,720
returned...

240
00:12:55,880 --> 00:12:58,600
So they can be used
as button triggers,

241
00:12:58,760 --> 00:13:02,960
as callbacks in web applications...
These can be blocks.

242
00:13:04,480 --> 00:13:06,560
We've already seen block usage.

243
00:13:06,720 --> 00:13:08,800
In iterators you have blocks.

244
00:13:08,960 --> 00:13:11,680
We saw blocks were used
in conditions.

245
00:13:11,840 --> 00:13:13,600
There'll be a course about blocks.

246
00:13:13,840 --> 00:13:16,440
It's elegant,
it was introduced in Eiffel,

247
00:13:16,600 --> 00:13:19,200
it was recently introduced in Java 8,

248
00:13:19,360 --> 00:13:21,800
there was a first version in C#...

249
00:13:21,960 --> 00:13:23,200
So it's fundamental.

250
00:13:23,360 --> 00:13:26,320
Blocks are a fundamental element

251
00:13:26,480 --> 00:13:30,400
of Pharo's syntax
and computational model.

252
00:13:30,720 --> 00:13:33,600
How do we define a class in Pharo?

253
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The browser you see here
shows you packages.

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You have the classes inside.

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And it shows you a template.

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The template is saying that
by default you inherit an object,

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and the name of the class.

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We'll see it for the class Point,
for example.

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So the definition of the class...

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I have the class object.
It's also a message!

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The message subclass:
InstanceVariableNames:

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blah blah blah...

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With...

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I define the class Point,

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and I give the instance variables
x and y.

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That's just to show the syntax always
follows the same model with messages.

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You don't usually write it out
by hand.

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The tool gives you the template
and you just fill it in.

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So how do we define a method?

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As I said, the methods
are public and virtual,

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and by default return self.

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So, when you're in the browser,

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it suggests a template,

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the name of the potential method
and a comment...

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We're nice and polite
so we comment on our code.

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We can also put temporary
variable names and statements.

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What does this gives us?
We've seen the method factorial.

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Here I'm in the class Integer.

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I look at the method factorial,
I have its code,

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with the name of the method,
its comment

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and the core of the method
that I've defined.

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So, to sum up, what have we seen?

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There are 3 kinds of messages:
unary messages, without arguments,

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binary messages,
where the selectors are mathematical,

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and keyword messages,
where there can be several arguments.

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There's a priority:
parentheses first,

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then unary, binary and keyword.

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And if there are same-level messages
it's from left to right.

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What have we seen?
The syntax is very compact.

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There are few constructs
but they're really expressive.

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It's mainly messages
and lexical closures, or blocks.

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There are three kinds of messages.

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You'll do an exercise
to develop a language.

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Like that you can define what we call
Domain Specific Languages.