Checking Matrix Elements

Function check.m may accelerate debugging of a program. The function displays columnwise elements of a real, complex or string matrix, say A, obeying a condition Cond. The output of every element A(p,q) fitting Cond consists of items <row number p> <column number q> <element value A(p,q)> in a required format.

Forms of calls:
~~~~~~~~~~~~~~~
check(A) % outputs all elements of matrix A
check(A,Cond) % outputs elements fulfilling Cond
check(A,Cond,form) % ditto in a required format
% A, a matrix of numerical elements to be checked
% Cond, a condition put on the matrix elements (string);
% default condition 'A==A' => output full matrix
% form, a format of element output; default format '%13.4e'

Examples:
~~~~~~~~~
k=(1:5).^2;
check(k,'k<10','%5i') % displays
% 1 1 1
% 1 2 4
% 1 3 9

check(k,'k>10')
% 1 4 1.6000e+001
% 1 5 2.5000e+001

Z = [1 i; -i 1];
check(Z)
% 1 1 1.0000e+000
% 2 1 0.0000e+000 -1.0000e+000*i
% 1 2 0.0000e+000 +1.0000e+000*i
% 2 2 1.0000e+000

s = 'This is a string';
check(s, 's==double(''i'')', ' %s')
% 1 3 i
% 1 6 i
% 1 14 i