function theResult = int2english(x)

% int2english -- English name of an integer.
%  int2english(x) returns or displays the English
%   name of x, an integer, up to about 10^22.
%  int2english('demo') demonstrates itself with
%   a random integer.
 
% Copyright (C) 1999 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 29-Dec-1999 05:55:08.
% Updated    29-Dec-1999 07:36:13.

if nargout > 0, theResult = []; end

if nargin < 1, x = 'demo'; end

if isequal(x, 'demo')
	help(mfilename)
	u = fix(rand(1, 1) * 100000);
	v = feval(mfilename, u);
	disp([' ## ' mfilename '(' int2str(u) ') = ' v])
	return
end

if ischar(x), x = eval(x); end

theNames = {
	'zero'
	'thousand'
	'million'
	'billion'
	'trillion'
	'quadrillion'
	'quintillion'
	'sextillion'
	'septillion'
	'octtillion'
	'nonillion'
	'decillion'
};

x = fix(x);
isNegative = x < 0;
x = abs(x);

y = '';

if x < 20
	y = do1(x);
elseif x < 100
	y = do2(x);
else
	k = 0;
	while x > 0
		a = rem(x, 1000);
		if a > 999
			disp([' ## Too big for Matlab "rem": ' num2str(x)])
			break
		elseif a > 0
			temp = do3(a);
			if k > 0
				temp = [temp ' ' theNames{k+1}];
			end
			if ~isempty(y), y = [' ' y]; end
			y = [temp y];
		end
		k = k+1;
		x = fix(x/1000);
	end
end

if isNegative, y = ['minus ' y]; end

if nargout > 0
	theResult = y;
else
	disp(y)
end


% ---------- do3 ---------- %


function y = do3(x)

% do3 -- Name of an integer < 1000.
%  do3(x) returns the name of integer x < 1000.

if x < 100
	y = do2(x);
else
	a = fix(x/100);
	b = rem(x, 100);
	y = [do1(a) ' hundred'];
	if b > 0
		y = [y ' ' do2(b)];
	end
end


% ---------- do2 ---------- %


function y = do2(x)

% do2 -- Name of an integer < 100.
%  do2(x) returns the name of integer x < 100.

theNames = {
	'zero'
	'ten'
	'twenty'
	'thirty'
	'forty'
	'fifty'
	'sixty'
	'seventy'
	'eighty'
	'ninety'
};

if x < 20
	y = do1(x);
else
	a = fix(x/10);
	b = rem(x, 10);
	y = theNames{a+1};
	if b > 0
		y = [y ' ' do1(b)];
	end
end


% ---------- do1 ---------- %


function y = do1(x)

% do1 -- Name of an integer < 20.
%  do1(x) returns the name of integer x < 20.

theNames = {
	'zero'
	'one'
	'two'
	'three'
	'four'
	'five'
	'six'
	'seven'
	'eight'
	'nine'
	'ten'
	'eleven'
	'twelve'
	'thirteen'
	'fourteen'
	'fifteen'
	'sixteen'
	'seventeen'
	'eighteen'
	'nineteen'
};

y = theNames{x+1};