callhelp.m

数字通信第四版原书的例程

function err = callhelp(file, method, addition);
%CALLHELP Calls a specified section of a help file to display.
%       CALLHELP(FILE) displays a entire FILE contents in the MATLAB
%       workspace.
%
%       CALLHELP(FILE, STR) searches [STR '_help_begin'] and [STR '_help_end']
%       in FILE and displays the section in the MATLAB workspace.
%
%       CALLHELP(FILE, STR, ADDITION) displays additional information with a
%       line break.
%
%       ERR = CALLHELP(...) output error message.
%       ERR = 0, command is successfully executed.
%       ERR = -2, file has not been  found.
%
%       See also: AMOD, ADEMOD, DMOD, DDEMOD, AMODCE, ADEMODCE, ENCODE, DECODE.

%       Wes Wang 1/16/95, 9/30/95
%       Copyright (c) 1995-96 by The MathWorks, Inc.
%       $Revision: 1.1 $  $Date: 1996/04/01 17:52:34 $

% help lines for individual modulation method.
hand = fopen(file);
if hand<=0
    error('The Communications Toolbox on your machine is not a completed one.')
else
    x = fscanf(hand, '%c', Inf);
    index_begin = findstr(x, [method,'_help_begin']);
    index_end = findstr(x, [method,'_help_end']);
    if index_end > index_begin
         x = x(index_begin+13+length(method):index_end-1);
        fprintf('%s', x);
        if nargin > 2
            disp(' ')
            disp(['       ', addition])
        end;
        if nargout > 0
            err = 0;
        end;
    else
        disp(['No help for ', method]);
        if nargout > 0
            err = -2;
        end;
    end;
end;
fclose(hand);
% end of callhelp.