In Erlang, you can define and call functions using the following syntax:
To define a function:
- Start with the keyword "fun" followed by the function name.
- Specify the function parameters within parentheses.
- Use the " -> " operator to separate the parameter list from the function body.
- Write the function body, which can contain one or more expressions.
- End the function definition with the keyword "end".
Example of function definition:
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double(X) -> X * 2. |
To call a function:
- Write the function name followed by the arguments in parentheses.
Example of function call:
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Result = double(5).
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In this example, the function "double" gets called with the argument "5" and the result is stored in the variable "Result".
You can also define functions that take multiple parameters, pattern match on function arguments, use guards for conditional evaluation, and more. Functions in Erlang can be defined globally or locally within a module. They are an essential part of writing Erlang programs as they allow encapsulating code into reusable units.
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What is function arity in Erlang?
In Erlang, function arity refers to the number of arguments that a function accepts. Every function in Erlang is defined with a fixed number of arguments, and this number is known as the arity of the function.
For example, a function with arity 3 would accept three arguments, while a function with arity 0 is a zero-arity function, also known as a nullary function, which does not accept any arguments.
Erlang uses pattern matching to determine which function clause to execute based on the number and values of the arguments provided during function invocation. It is important to specify the correct arity while defining and calling functions in Erlang to ensure proper execution.
What is the purpose of exporting functions in Erlang modules?
The purpose of exporting functions in Erlang modules is to make those functions accessible to other modules or applications. When a function is exported, it means that other modules can use that function and call it from their code.
Exporting functions is necessary in Erlang because modules encapsulate code and data, and functions that are not exported are not accessible from outside the module. This allows for better code organization and modularity, as well as information hiding, as only the exported functions are part of the module's public interface.
By selectively exporting functions, developers can control which functions are visible to other modules and which are private or internal to the module. This allows for better code reuse, readability, and maintainability, as only the necessary functions are exposed and used by other modules.
What is the syntax for defining a function in Erlang?
In Erlang, you can define a function using the following syntax:
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function_name(Parameters) -> % Function body. |
Here's an example of a function called factorial that calculates the factorial of a given number:
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factorial(0) -> 1; factorial(N) when N > 0 -> N * factorial(N - 1). |
In this example, the factorial function takes a parameter N. It has two clauses: one for the base case when N is 0, which returns 1, and another for the recursive case when N is greater than 0. The recursive case calculates the factorial by multiplying N with the factorial of N - 1.
Note that Erlang uses pattern matching to determine which clause of the function to execute based on the given arguments.
What is the purpose of an anonymous function in Erlang?
The purpose of an anonymous function in Erlang is to create a function without assigning it a name. Anonymous functions are often used as arguments to other functions or as return values from functions. They provide a way to define and pass around small, independent pieces of code. Anonymous functions are commonly used in higher-order functions, such as map, filter, and fold, where they can be used to apply a certain operation to each element of a list or collection. Additionally, anonymous functions allow for code modularity and abstraction, making it easier to write concise and reusable code.
What is the default return value of a function in Erlang?
The default return value of a function in Erlang is undefined. If a function does not explicitly return a value, Erlang automatically returns undefined as the default value.
How to define a module in Erlang?
To define a module in Erlang, follow these steps:
- Open a new file with the ".erl" extension, for example, "my_module.erl".
- At the beginning of the file, use the "-module(ModuleName)." directive to define the module name. Replace "ModuleName" with the desired name of your module. For example:
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-module(my_module).
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- Optionally, you can specify the export functions using the "-export([Function1/Arity, Function2/Arity, ...])." directive. This step is necessary if you want to make specific functions accessible outside the module. Specify the names and arities of the functions you want to export within the square brackets. For example:
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-export([add/2, subtract/2]).
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- Define the functions of your module. For example, you can create an "add/2" function that adds two numbers:
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add(X, Y) -> X + Y. |
- Save the file with the ".erl" extension, for example, "my_module.erl".
- Compile the module by executing the following command in the Erlang Shell (replacing "my_module" with the actual name of your module):
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c(my_module).
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The module is now defined and ready to be used. You can call the defined functions using the module name followed by a dot, for example, "my_module:add(2, 3)".
