Branching and If-constructs

a = input('Enter a number:');
if isnumeric(a) && (a >= 0)
    root = sqrt(a);
    disp(['Square root(',num2str(a),') = ', num2str(root)]);
elseif isnumeric(a) && (a < 0)
    disp(['The input number is negative, there is no square root.']);
else
    disp(['Please enter a real number!']);
end

if isequal(size(A),size(B))
   C = [A; B];
else
   disp('A and B are not the same size.')
   C = [];
end

if exist('myScript.m','file')
    disp('Your file exists! Did you expect otherwise?')
else
    disp('Your file does not exist! Then perhaps you don''t exist either??')
end

x = input('input the value of x: ')
if x >= -1 && x <= 1
    y = x
else
    y = x^2
end
disp(['y(x=',num2str(x),') = ',num2str(y)])

day = input('Enter a day number:');
switch day
    case 1
        day_name = 'Monday';
    case 2
        day_name = 'Tuesday';
    case 3
        day_name = 'Wednesday';
    case 4
        day_name = 'Thursday';
    case 5
        day_name = 'Friday';
    case 6
        day_name = 'Saturday';
    case 7
        day_name = 'Sunday';
    otherwise
        day_name = 'Unknown';
end
disp(['The corresponding weekday is ',day_name,'.'])

day = input('Enter a day number:');
switch day
    case {1,2,3,4,5}
        day_name = 'Weekday';
    case {6,7}
        day_name = 'Weekend';
    otherwise
        day_name = 'Unknown';
end
disp(['The input day number corresponds to ',day_name,'.'])

if 5.6
    disp('The condition in this if statement is automatically converted from float to boolean')
end

if ~0.0
    disp('A float value of zero is converted to false')
end

if 0.0
    disp('A float value of zero is converted to false')
end

if 0.000000000000000000000000000000000000000000000000000000000000000000001
    disp('Any non-zero float value of any precision is converted to true')
end

if 1.e-323
    disp('Any non-zero float value of any precision is converted to true')
end

if 1.e-324 % make sure you don't go beyond computer precision
    disp('Any non-zero float value smaller than the computer precision will be set to 0')
end

if ~1.e-324 % make sure you don't go beyond computer precision
    disp('Any non-zero float value smaller than the computer precision will be set to 0')
end

if 12
    disp('The same rules also hold for integers.')
end

if ''
    disp('An empty string is always converted to boolean false, because it is considered an empty logical vector.')
end

if ''
else
    disp('An empty string is always converted to boolean false, because it is considered an empty logical vector.')
end

if []
else
    disp('An empty vector is always converted to boolean false, because it is considered an empty logical vector.')
end

if {}
    disp('An empty cell cannot be converted to boolean value, because MATLAB wants it that way!')
end

if ['amir']
    disp('A non-empty vector is converted to boolean true.')
end

if ' '
    disp('A non-empty string is converted to boolean true.')
end