%% Using the REGEXP regular expression matching funcion
% The REGEXP function is used for matching regular expressions. This
% example shows how you can find files with the .m extension in a
% particular directory. The standard help for the REGEXP function can be
% seen be typing "help regexp" or "doc regexp" at the MATLAB command line.

% Get current directory contents

generalFunctions = dir;

% Get all the filenames, fileNames is a cell array of file names.

fileNames = {generalFunctions.name}

% We now use the regexp function to find the file names with a .m
% extension. The expression '.\.m\>' is interpretted as follows:
%
% 1) The first '.' means 'match any character'. We only want names with a
% .m extension so we dont care what the rest of the file name is.
%
% 2) The '\.m' expression indicates '.m'. The backslash is necessary to
% specify a fullstop rather than the before mentioned 'match any
% character' specifier.
%
% 3) The '\>' expression means 'the ".m" string must be at the END of the
% expression'. The is necessary so that we can dont return, for example,
% files with an extension of .mat.
%
% REGEXP returns a cell array containing the position of the ".m" in the
% file name, if the name has a .m extension, or an empty cell.

regexpResult = regexp(fileNames,'.\.m\>')

% We want to convert regexpResult into a logical index so that we can find
% the .m files. We use the CELLFUN function with the 'isempty' option in
% order to convert the 'regexpResult' cell array into a logical index.
%
% 'logicalIndex' is a vector of logical values (ones and zeros) and is the
% same length as 'fileNames'. A value of '1' indicates where a file name with
% a .m extension exists in the fileNames cell array. A value of '0'
% indicates where a file does not have a .m extension.

logicalIndex = ~cellfun('isempty',regexpResult)

% We now index into the file names with the logical index in order to get
% all the .m files:

fileNames(logicalIndex)

% The last three lines of code can be performed in one line of code:

fileNames(~cellfun('isempty',regexp(fileNames,'.\.m\>')))