Citrine (programming language): Difference between revisions

Revision as of 10:53, 28 March 2016

Revision as of 04:06, 21 April 2016

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Citrine has a very limited syntax and it's very closely related to Smalltalk. Everything in Citrine is an ''object'', there are 5 literals:

* {{code|Nil}}

<source lang="citrine">

* {{code|True, False}}

* Nil

* {{code|0,1,2,3}}

* True False

* {{code|'String'}}

* 0,1,2,3

* <code>{ param | ...block of code... }</code>

* 'String'

* { param | ...block of code... }

</source>

The code block literal uses a ''pipe'' symbol to separate the parameters from the logic '|', if there are no

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A Citrine program is basically a sequence of messages sent to objects. For instance, to calculate the factorial of the number 5, the message 'factorial' is sent to the number 5.

<source lang="citrinesmalltalk">

5 factorial.

</source>

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This is called a ''unary'' message because it takes no arguments. A ''binary'' message is always a single UTF-8 character; this differs from Smalltalk, where there is a fixed set of binary messages. Here is an example:

<source lang="citrinesmalltalk">

6 + 7.

</source>

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Here a binary message '+' is sent to number 6, the argument of this binary message is '7', this will result in a new number object '13'. Assigning the outcome of this operation to a variable uses the assignment operator: :=.

<source lang="citrinesmalltalk">

total := money + debt.

</source>

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Also note that each line in a Citrine program ends with a dot, just like in Smalltalk. Besides unary and binary messages, Citrine offers ''keyword messages'', which take arguments interspersed with the message itself just like Smalltalk and [[Objective-C]].

<source lang="citrinesmalltalk">

3 between: 1 and: 5.

</source>

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Just like Smalltalk, control flow in Citrine is implemented by strategic use of messages. For instance, writing a conditional statement requires sending a block of code to a boolean.

<source lang="citrinesmalltalk">

(money >= price) ifTrue: {\ Pen write: 'Yes, you can afford this'. }.

</source>

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Likewise, a for-loop is written as:

<source lang="citrinesmalltalk">

1 to: 10 step: 1 do: { step | Pen write: 'this is step:' + step. }.

</source>

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Besides for-loops, Citrine features each-loops, while-loops and a simple times loop, the latter uses the binary message '*'.

<source lang="citrinesmalltalk">

7 * { step | Pen write: 'this is step:' + step. }.

</source>

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To break out of a loop in Citrine one has to send the message 'break' to a boolean, this allows a conditional break from a loop without having to factor out the break conditions:

<source lang="citrinesmalltalk">

#0-4

0 to: 10 step: 1 do: { i |

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Unlike Smalltalk, Citrine has no semi-colon to send a message to the original receiver. Instead Citrine has a comma token ',' used to chain keyword messages, this allows writing Unix-like ''[[Pipeline (Unix)|pipelines]]''. The following code uses a pipeline-like syntax to replace all the 'o' characters with zeroes, the resulting string would be something like: '1010101...'.

<source lang="citrinesmalltalk">

onesAndZeroes := '1o1o1o1o1o1' split: 'o', map: mapUp, join: '0'.

</source>

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The biggest difference from Smalltalk is the use of prototypes. Citrine does not have a concept of a class, it only knows about objects. An object is created using the new message:

<source lang="citrinesmalltalk">

cat := Object new.

</source>

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adding methods in languages like [[Java (programming language)|Java]]:

<source lang="citrinesmalltalk">

cat on: 'meow' do: {\

Pen write: 'meow!'.

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As stated above, inheritance is based on prototypes. To derive an object from another object, the new message must be sent to the object to be extended:

<source lang="citrinesmalltalk">

Animal := Object new.

Animal on: 'makeSound' do: {\

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Citrine uses UTF-8 unicode extensively, both objects and messages can consist of unicode symbols. All string length are calculated using UTF-8. Citrine distinguishes string length and size in bytes:

<source lang="citrinesmalltalk">

'text' length.

</source>

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returns the length of the string in UTF-8 code pointes, while:

<source lang="citrinesmalltalk">

'text' bytes.

</source>

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Demonstration:

<source lang="citrinesmalltalk">

Application := {\

var mailer := Mailer new. #make mailer available to all modules