inv.hhs

/**
 * @author Jason Reynolds
 * @param input - the matrix to be inverted, Mat or JS array
 * @returns - the inverted matrix
 * 
 * Function that given a square invertible matrice, it will return the inverted matrix
 */




function inv(input) {

    *import math: ndim
    *import math: det
    *import math: deep_copy

    if (arguments.length === 0) {
        throw new Error('Exception occurred in inv - no argument given');
    }
    else if (arguments.length > 1) {
        throw new Error('Exception occurred in inv - wrong argument number');
    }

    if (!(Array.isArray(input)) && !(input instanceof Mat) && !(input instanceof Tensor)) {
        throw new Error('Exception occurred in inv - input must be a 2-dimensional JS array, matrix or tensor');
    }

    //declare raw_in to be a clone of input if Mat otherwise input itself 
    let in_type = (input instanceof Mat) || (input instanceof Tensor)
    let raw_in = (in_type) ? input.clone() : deep_copy(input);

    //when an instance of Mat degrade to JS array to generalize preceeding code
    if (in_type) {
        raw_in = raw_in.val;
    }
    //if the ndim is not 2 i.e. not a 2d matrix, throw an error 
    if (!(ndim(input) === 2)) {
        throw new Error('Exception occurred in inv - not a 2d matrix, either wrong formatting or wrong dimensions')
    }
    //if row length =/= col length throw error
    if (!(raw_in.length === raw_in[0].length)) {
        throw new Error('Exception occurred in inv - not a square matrix');
    }
    //if det === 0 it's not invertible, throw error
    if (det(raw_in) === 0) {
        throw new Error('Exception occurred in inv - det is zero, not invertible');
    }
    //if it is ndim 2 or input is of instance Mat (not necessary?), finally return the inverse as a Mat object
    if (ndim(raw_in) === 2 || input instanceof Mat) {
        return new Mat(mathjs.inv(raw_in));
    }
}