程序代码求助？

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data _null_;
array x[5] $3 ('ant' 'bee' 'cat' 'dog' 'ewe');
n=dim(x); k=3;
ncomb=comb(n,k);
do j=1 to ncomb+1;
rc=allcomb(j, k, of x[*]);
put j 5. +3 x1-x3 +3 rc=;
我的问题是，ALLCOMB函数运行原理是什么？即：从5个变量抽出3个，单独放置出来？还是变量不动，只是指针变动？

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关键词：程序代码 array Data 我的问题 null 程序

COMB(n,k) function computes the number of combinations of n elements taken k at a time.
ALLCOMB(j, k, of x[*]) function generates all combinations of the values of j variables taken k at a time in a minimal change order.

For the ALLCOMB function, the following actions occur:
1.On the first execution, ALLCOMB returns 0.
2.If the values of variable-i and variable-j were interchanged, where i<j, then ALLCOMB returns i.
3.If no values were interchanged because all combinations were already generated, then ALLCOMB returns –1.

davil2000 发表于 2012-11-22 08:27
COMB(n,k) function computes the number of combinations of n elements taken k at a time.
ALLCOMB(j, ...

达人可否就上边那个例子来分析下？？