In Erlang, you can multiply lists of lists together by using list comprehensions or recursive functions. Here's an explanation of the process:

**Using list comprehensions**: Define two lists of lists that you want to multiply, for example, ListA and ListB. Iterate over both lists simultaneously using a list comprehension. Multiply corresponding elements from each list and create a new list containing the multiplied values. Repeat this process for each inner list. The final result will be a new list of lists containing the multiplied values.**Using recursive functions**: Define a recursive function that takes two lists of lists as parameters. Extract the first element from each list of lists. Multiply the extracted elements and add the result to a new list. Call the recursive function again with the remaining elements of the lists. Repeat this process until all elements are multiplied. The final result will be a new list of lists containing the multiplied values.

Both approaches provide a way to multiply lists of lists in Erlang, and you can choose the one that suits your requirements and coding style.

## How to multiply lists element-wise in Erlang?

One way to multiply lists element-wise in Erlang is to use a loop and recursively multiply the corresponding elements of the two lists. Here is an example implementation:

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-module(multiply_lists). -export([multiply/2]). multiply(List1, List2) -> multiply(List1, List2, []). multiply([], [], Result) -> lists:reverse(Result); multiply([X|Xs], [Y|Ys], Result) -> multiply(Xs, Ys, [X*Y|Result]). |

In this example, the `multiply/2`

function takes two input lists and calls the helper function `multiply/3`

with an additional empty list `[]`

as the initial accumulator.
The `multiply/3`

function defines two base cases: when both lists are empty, it returns the accumulated result after reversing it using `lists:reverse/1`

; and when both lists have elements, it multiplies the corresponding elements and appends the result to the accumulator. It then makes a recursive call with the remaining elements of both lists and the updated accumulator.

## How to multiply a list of lists with a non-square matrix in Erlang?

To multiply a list of lists with a non-square matrix in Erlang, you can use the following code:

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% Function to multiply a list of lists with a non-square matrix multiply_lists(Matrix, Lists) -> lists:map(fun(List) -> multiply_list(Matrix, List) end, Lists). % Helper function to multiply a single list with a matrix multiply_list(Matrix, List) -> lists:flatten(lists:zipwith(fun(Row, Value) -> multiply_row(Row, Value) end, Matrix, List)). % Helper function to multiply a row of the matrix with a value multiply_row(Row, Value) -> lists:map(fun(X) -> X * Value end, Row). |

Here's how you can use the above code:

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Matrix = [[2, 4, 6], [1, 3, 5], [7, 8, 9], [0, -1, 2]], Lists = [[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12]], Result = multiply_lists(Matrix, Lists). |

In this example, `Matrix`

represents the non-square matrix and `Lists`

is the list of lists you want to multiply with the matrix. The `multiply_lists`

function takes in both `Matrix`

and `Lists`

and returns the result of multiplying each list in `Lists`

with the Matrix. The `multiply_list`

function is a helper function that multiplies a single list with the matrix by performing element-wise multiplication of each row in the matrix with the corresponding value in the list. Finally, the `multiply_row`

function is another helper function that performs the element-wise multiplication of a row in the matrix with a single value.

The `Result`

variable will contain the resulting list of lists after the multiplication.

## What is the result of multiplying an empty list in Erlang?

The result of multiplying an empty list in Erlang is usually an error. In Erlang, the multiplication operator (*) is used for arithmetic operations, so attempting to multiply an empty list will throw a badarith error. This is because multiplication is not defined for lists in Erlang.

## What is the operator used for list multiplication in Erlang?

In Erlang, the operator used for list multiplication is the `++`

operator. This operator is used to concatenate two lists together. Here's an example of how it is used:

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List1 = [1, 2, 3], List2 = [4, 5, 6], Concatenated = List1 ++ List2. |

In this example, the `++`

operator is used to concatenate `List1`

and `List2`

, resulting in the list `[1, 2, 3, 4, 5, 6]`

.