checkBlankLines

Checks the number blank lines that are permitted or required between and around code.

Configurable parameters

ItemTypes: List of item types the rule applies to. Options are:
- arguments: arguments block.
- case: case and otherwise. Since cases do not have an explicit end the MinAfter and MaxAfter settings are ignored.
- code: Any non-blank line that does not fall in any of the other categories.
- comment: Any line that only contains a comment.
- classdef: classdef block.
- if: if block.
- enumeration: enumeration block.
- events: events block.
- for: for block.
- function: function block. When functions without explicit end are used, the MinAfter and MaxAfter settings are ignored.
- methods: methods block.
- parfor: parfor block.
- properties: properties block.
- spmd: spmd block.
- switch: switch block.
- try: try block.
- while: while block.

Levels: Range of nesting levels the rule applies to, e.g.: 1 Inf matches nesting level 1 and above. The nesting level does not depend on indentation.

function y = f(u)   % 0
    persistent x;   % 1 <-- The rule applies to this line.

    if isempty(x)   % 1 <-- The rule applies to this line.
        x = 0;      % 2 <-- The rule applies to this line.
    end             % 1 <-- The rule applies to this line.

    y = x;          % 1 <-- The rule applies to this line.
    x = u;          % 1 <-- The rule applies to this line.
end                 % 0

function y = f(u)   % 0
persistent x;       % 1 <-- The rule applies to this line.

if isempty(x)       % 1 <-- The rule applies to this line.
x = 0;              % 2 <-- The rule applies to this line.
end                 % 1 <-- The rule applies to this line.

y = x;              % 1 <-- The rule applies to this line.
x = u;              % 1 <-- The rule applies to this line.
end                 % 0

MinBefore: Minimum number of consecutive blank lines before the item. If one or more comments are directly above the item, the rule applies above these comments.

if isempty(x) % <-- The rule applies to this line.
    x = 0;
end

% Initialize when empty. <-- The rule applies to this line.
% Default value: 0.
if isempty(x)
    x = 0;
end

MaxBefore: Maximum number of consecutive blank lines before the item. If one or more comments are directly above the item, the rule applies above these comments (see MinBefore).
MinAfter: Minimum number of consecutive blank lines after the item.
MaxAfter: Maximum number of consecutive blank lines after the item.

FirstLastInBlock: How to treat the first and last non-blank line in a block. Options are:

none: No blank lines before the first line or after the last line in the block are permitted.
min: The number of blank lines before the first line in the block must be MinBefore and the number of blank lines after the last line in the block must be MinAfter.
check min: The number of blank lines before the first line in the block must be greater than or equal to MinBefore and the number of blank lines after the last line in the block must be greater than or equal to MinAfter.
check min/max: The first and last line in the block are treated the same as any other line.
check max: The number of blank lines before the first line in the block must be less than or equal to MaxBefore and the number of blank lines after the last line in the block must be less than or equal to MaxAfter.
max: The number of blank lines before the first line in the block must be MaxBefore and the number of blank lines after the last line in the block must be MaxAfter.

if x                            % <-- begin of block
    a = 1;                      % <-- first line in block
    b = 2;
    c = 3;                      % <-- last line in block
end                             % <-- end of block

if x                            % <-- begin of block
    % Initialize a, b and c.      <-- first line in block
    a = 1;
    b = 2;
    c = 3;                      % <-- last line in block

end                             % <-- end of block

switch y                        % <-- begin of block
    case 1                      % <-- begin of block & first line in block
        a = 1;                  % <-- first line in block
        b = 2;                  % <-- ignored (see ItemType)
        
    case 2                      % <-- begin of block
        a = 2;                  % <-- first line in block
        b = 3;                  % <-- ignored (see ItemType)

    otherwise                   % <-- begin of block
        a = 3;                  % <-- first line in block
        b = 4;                  % <-- last line in block
end                             % <-- end of block

Exemption tag: %@ok<BLALN>