[求助]function 问题

[xiaotie]

我编了一个如下
function [y,n]=jacobi(A,b,x0,eps)
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??? function [y,n]=jacobi(A,b,x0,eps)
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Error: Function definitions are not permitted at the prompt or in scripts.
打入
HELP function
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Warning: Could not find an exact (case-sensitive) match for 'HELP'.
I:\Program Files\MATLAB71\toolbox\matlab\helptools\help.m is a case-insensitive match and will be used instead.
You can improve the performance of your code by using exact
name matches and we therefore recommend that you update your
usage accordingly. Alternatively, you can disable this warning using
warning('off','MATLAB:dispatcher:InexactMatch').
FUNCTION Add new function.
New functions may be added to MATLAB's vocabulary if they
are expressed in terms of other existing functions. The
commands and functions that comprise the new function must
be put in a file whose name defines the name of the new
function, with a filename extension of '.m'. At the top of
the file must be a line that contains the syntax definition
for the new function. For example, the existence of a file
on disk called STAT.M with:

function [mean,stdev] = stat(x)
%STAT Interesting statistics.
n = length(x);
mean = sum(x) / n;
stdev = sqrt(sum((x - mean).^2)/n);

defines a new function called STAT that calculates the
mean and standard deviation of a vector. The variables
within the body of the function are all local variables.
See SCRIPT for procedures that work globally on the work-
space.

A subfunction that is visible to the other functions in the
same file is created by defining a new function with the FUNCTION
keyword after the body of the preceding function or subfunction.
For example, avg is a subfunction within the file STAT.M:

function [mean,stdev] = stat(x)
%STAT Interesting statistics.
n = length(x);
mean = avg(x,n);
stdev = sqrt(sum((x-avg(x,n)).^2)/n);

%-------------------------
function mean = avg(x,n)
%AVG subfunction
mean = sum(x)/n;

Subfunctions are not visible outside the file where they are defined.
Normally functions return when the end of the function is reached.
A RETURN statement can be used to force an early return.

See also script, return, varargin, varargout, nargin, nargout,
inputname, mfilename.

Reference page in Help browser
doc function