284 lines
7.6 KiB
Markdown
284 lines
7.6 KiB
Markdown
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# The Noja language
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This documentation was intended for people who already program in other high level languages (such as Python, Javascript, Ruby) and don't need to be introduced to basic programming concepts like variables, expressions and branches). Not having to introduce common programming concepts leaves more space to the characteristics specific to this language.
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## Table of contents
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3. [The first program](#the-first-program)
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4. [Expressions](#expressions)
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5. [Branches](#branches)
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6. [Loops](#loops)
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7. [Functions](#functions)
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## A Noja program
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A Noja program is a list of statements that can be of multiple kinds (function delcarations, expressions, if-else branches, etc). Any whitespace, if not inside strings, is ignored. Comments start with the `#` character and end with the line. There are no multi-line comments.
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## Expressions
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The most basic type of statement is an expression. They work similarly to other languages. The basic types of values are
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```py
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3; # Integers:
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# They are represented internally by 64 bits and are always signed, therefore
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# the minimum value representable is -2^63 and the maximum is 2^63-1.
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3.4; # Floats
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# Like integers, they are represented using 64 bits.
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"hello!"; # Strings:
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'hello!'; # They represent text. They are encoding-agnostic, because it treats
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# them as sequences of bytes. This may not be the most ergonomic choice,
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# but it was the simplest one.
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true; # Booleans:
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false; # Nothing new here. They represent two values that have the property of being
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# each other's logical negation.
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none; # The none value:
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# This is specific to the language. It can be used to represent the absence of
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# a value when one was expected. It's only propery is to be identical to and
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# only to itself.
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[1, 2, none, false]; # Lists:
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# They are ordered and etherogenic collections of values.
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# Nested values can be accessed by their index relative to the
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# start.
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{ 1: 'hello', true: [1, 2]} # Maps:
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# Maps are a list of associations between values. You can
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# see them as a list of key and value pairs. The values
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# are the content of the map and the keys are what you
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# use to access them. Both keys and values can be any type
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# of value.
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```
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there are also other types of values (like functions and buffers) but they'll be covered further on.
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This language is stricter than others in regards to type conversions and on what types you can apply operators.
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### Operators
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Operators in noja genererally behave like you would expect.
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Arithmetic operators can only be used on numeric values
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```py
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+1; # 1
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-1; # -1
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1 + 1; # 2
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1 - 2; # -1
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3 * 2; # 6
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10 / 3; # 3
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10 / 3.0; # 3.33..
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10.0 / 3; # 3.33..
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```
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If the operands are integers, the result also will. If a float is involved, then the result is also a float. The only relevant thing to note here is that the division between integers results in a rounding down of the float version.
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Relational operators also can only be applied on numeric types, exception made only for `==` and `!=`, which can be used to compare any type of value. These operations always result in a boolean value.
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```py
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1 < 2; # true
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1 > 2; # false
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1 >= 0; # true
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1 <= 0; # false
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1 == 1; # true
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1 != 1; # false
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```
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Logical operators can only be applied on booleans and also always return booleans:
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```py
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not true; # false
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not false; # true
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true and true; # true
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true and false; # false
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false and true; # false
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false and false; # false
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true or true; # true
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true or false; # true
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false or true; # true
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false or false; # false
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not 1; # ERROR!
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```
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### Variables
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Variable names can contain letters, digits and underscores (the first character can't be a digit though). You can set variables without declaring them first:
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```py
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a = 5;
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```
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which is similar to Python's assignment, but is a little different. In this language, assignments are considered as expressions, in fact you can do things like
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```py
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a = (b = 1) + 1;
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# The value resulting from an assignment is the assigned value.
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# After this expression, b's value is 1 and a's value is 2.
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print('b = ', b, '\n'); # b = 1
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print('a = ', a, '\n'); # a = 2
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```
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## Branches
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Like in every other language, it's possible to make the execution of one or more statements optional.
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```py
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if 1 < 2:
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print('Took the branch!\n'); # This is executed!
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if 1 > 2:
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print('Didn\'t take the branch\n'); # This isn't!
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```
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..or you can specify an alternative branch, which is executed when the
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condition isn't true:
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```py
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if 1 > 2:
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print('Not executed..\n');
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else
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print('Executed!\n');
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```
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You can have multiple statements inside a branch by having them inside a
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compound statement. Compound statements are statement lists wrapped inside
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curly brackets, like this:
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```py
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{ print('Hello from a '); print('compound statement!\n'); }
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```
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This way they count as one statement.
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```py
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if 1 == 1: {
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print('Executed\n');
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print('Also executed\n');
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}
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```
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Variables defined inside an if-else statement's branch are defined
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in the parent's context. This implies that variables may or may not
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be defined when you access them, based on which branch is taken.
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```py
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a = 1;
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if a < 2:
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x = 100;
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# Now x is defined, but if "a" were to be higher or equal to 2, it
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# wouldn't be defined and the runtime would return an error.
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```
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## Loops
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Looping constructs are available in the form of while and do-while
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statements. The while statement checks the condition before each
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iteration:
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```py
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i = 0;
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while i < 10:
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i = i + 1;
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```
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This loop runs for 10 times. As for the if-else statement, a single
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statement is expected as the body of the while statement. You can
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provide it a compound statement tho.
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```py
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i = 0;
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while i < 10:
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{
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print('While iteration no. ', i, '\n');
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i = i + 1;
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}
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```
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The do-while statement checks the condition at the end of each
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iteration. This means that at least one iteration is performed!
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```py
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i = 0;
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do
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{
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print('Do-while iteration no. ', i, '\n');
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i = i + 1;
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}
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while i < 10;
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```
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Like for if-else statements, variables defined inside the loop
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body are shared with the parent's context.
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## Functions
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Functions can be defined using the following syntax:
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```py
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# Define it
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fun say_hello_to(name)
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print('Hello, ', name, '!\n\n');
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# .. and then call it.
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say_hello_to('Francesco');
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```
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Functions can have an arbitrary amount of arguments. If the function is
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called with more arguments than it expected, the extra values are thrown
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away. If the function is called with less arguments than it expected,
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the argument set if filled up with none values.
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```py
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fun test_func(a, b, c)
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{
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print('a = ', a, '\n');
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print('b = ', b, '\n');
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print('c = ', c, '\n\n');
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}
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test_func();
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# a = none
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# b = none
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# c = none
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test_func(1, 2);
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# a = 1
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# b = 2
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# c = none
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test_func(1, 2, 3);
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# a = 1
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# b = 2
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# c = 3
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test_func(1, 2, 3, 4);
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# a = 1
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# b = 2
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# c = 3
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```
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Functions are actually variables like the ones that are be defined using
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the assignment operator. In fact, you can reassign them new values if you
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want.
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```py
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test_func = 5;
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# The following line, if executed, returns an error because the test_func
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# identifier is now associated to 5, which is not a function.
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test_func(); # Error!!
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```
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Functions can return values exactly like in other languages:
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```py
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fun multiply(x, y)
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return x * y;
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p = 4;
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q = 7;
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r = multiply(p, q);
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print(p, ' * ', q, ' = ', r, '\n');
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```
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If the function doesn't return any values, then the `none` value is returned.
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As an example, the `print` function always returns `none`
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```py
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print(print()); # none
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``` |