is_symmetric.hhs

/**
 * @author Jason Reynolds
 * @param input - the matrix to check if it's symmetric, needs to be square and 2d, can be Mat or JS
 * @returns  -  boolean value, true or false, depending on if if input is symmetric or not 
 * 
 * Function to check if the 2d matrix, raw array or Mat object is symmetric 
 * 
 */



//returns true if symmetric, false if not, throws exception if not correct dimensions or 0 dimensions
function is_symmetric(input) {


    *import math: transpose
    *import math: ndim
    *import math: deep_copy

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

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

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

    //in the case of input being Mat, degrade raw_in to JS array for generalized code
    if (in_type) {
        raw_in = raw_in.val;
    }
    //check: is matrix square? is any dimension 0? is ndim not 2? if so throw an error
    if ((!(ndim(raw_in) === 2)) || !(raw_in.length === raw_in[0].length) || raw_in.length === 0 || raw_in[0].length === 0) {
        throw new Error('Exception occurred in is_symmetric - either not square, not 2d, or 0 dimension row/cols');
    }
    //if the Mat object doesn't equal it's transpose, return false
    if (!(raw_in === (transpose(raw_in)))) {
        return false;
    }
    //otherwise if all above statements failed, then its of valid size and it's transpose is itself; it passed all tests ==> it's symmetric
    return true;
}