What is the difference between PHP functions and Haskell functions?

The difference between PHP and Haskell functions is: Function signature: Optional in PHP, mandatory in Haskell. Parameter types: PHP loose, Haskell strict. Return value type: Optional in PHP, mandatory in Haskell.

The difference between PHP functions and Haskell functions

PHP and Haskell are both popular programming languages, but they differ in function definitions and There are big differences in how they are used.

Function signature

• #PHP: Function signature is optional, you can not provide parameter types and return value types at any time.
• Haskell: Function signatures are mandatory and all parameter types and return value types must be specified.

Example:

// PHP
function add($a, $b) {
  return $a + $b;
}

-- Haskell
add :: Int -> Int -> Int
add a b = a + b

Parameter type

• ##PHP: Parameter Types are loose, meaning that any type of value can be passed.
• Haskell: Argument types are strict and must match the declared type of the function signature.

Example:

// PHP
add("1", 2); // 有效，但结果为 "12"

-- Haskell
add "1" 2 -- 类型错误：参数类型不匹配

Return value type

##PHP：
• The return type is optional, and the void keyword can be used to indicate that the function returns no value.
Haskell:
• The return value type is mandatory and must match the declared type of the function signature.

Example:

// PHP
function print_hello() {
  echo "Hello, World!";
}

-- Haskell
print_hello :: IO ()
print_hello = putStrLn "Hello, World!"

Practical example:

Consider a function that calculates the sum of elements in a list.

// PHP
function sum_list($list) {
  $sum = 0;
  foreach ($list as $item) {
    $sum += $item;
  }
  return $sum;
}

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