function r = int(f,x,a,b)
%符号积分法
% int(s)符号表达式s的不定积分.
% int(s,v)符号表达式s关于变量v的不定积分.
% int(s,a,b)符号表达式s的定积分, a,b分别为上﹑下限.
% int(s,v,a,b)符号表达式s关于变量v从 a到b的定积分.
% 当int求不出符号解,会自动转求数值解.
%例（ 求不出符号解,会自动转求数值解）
% syms x;t=int(exp(-x^sin(x)),0,1),vpa(t,5)
% 结果为
% Warning: Explicit integral could not be found.
% > In D:\MATLAB5\toolbox\symbolic\@sym\int.m at line 58
% t =
% int(exp(-x^sin(x)),x = 0 .. 1)%表示无解析解
% ans =
% .45491 %数值解
%更多的例子见下列英文部分
%
%INT Integrate.
% INT(S) is the indefinite integral of S with respect to its symbolic
% variable as defined by FINDSYM. S is a SYM (matrix or scalar).
% If S is a constant, the integral is with respect to 'x'.
% INT(S,v) is the indefinite integral of S with respect to v. v is a
% scalar SYM.
% INT(S,a,b) is the definite integral of S with respect to its
% symbolic variable from a to b. a and b are each double or
% symbolic scalars.
% INT(S,v,a,b) is the definite integral of S with respect to v
% from a to b.
%
% Examples:
% syms x x1 alpha u t;
% A = [cos(x*t),sin(x*t);-sin(x*t),cos(x*t)];
% int(1/(1+x^2)) returns atan(x)
% int(sin(alpha*u),alpha) returns -cos(alpha*u)/u
% int(besselj(1,x),x) returns -besselj(0,x)
% int(x1*log(1+x1),0,1) returns 1/4
% int(4*x*t,x,2,sin(t)) returns 2*sin(t)^2*t-8*t
% int([exp(t),exp(alpha*t)]) returns [exp(t), 1/alpha*exp(alpha*t)]
% int(A,t) returns [sin(x*t)/x, -cos(x*t)/x]
% [cos(x*t)/x, sin(x*t)/x]
% Copyright (c) 1993-98 by The MathWorks, Inc.
% $Revision: 1.15 $ $Date: 1997/11/29 01:05:44 $pj costa
f = sym(f);
if nargin % Indefinite integral
if nargin < 2
x = findsym(f,1);
if isempty(x), x = 'x'; end
else
x = char(sym(x));
end
r = maple('map','int',f,x);
else
% Definite integral
if nargin < 4
b = a;
a = x;
x = findsym(f,1);
if isempty(x), x = 'x'; end
end
x = sym(x);
b = sym(b);
a = sym(a);
r = maple('map','int',f,[x.s '=' a.s '..' b.s]);
end
if ~isempty(findstr('int(',char(r)))
for k = 1:prod(size(r));
rc = char(r(k));
if length(rc) >= 4 & isequal(rc(1:4),'int(')
warning('Explicit integral could not be found.')
end
end
end
