h.prod

来自「强大的数学工具包」· PROD 代码 · 共 39 行

                               * * * * * * *
                               *   prod    *
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        "product"
        SYNTAX: prod(x=l, u, exp)
                prod(l, u, exp)


        l and u are expressions whose values are integers.
        Remark: If u is an expression containing x (or @), u is 
                evaluated once at the beginning and remains fixed.
   
        exp is an expression whose value is an element of Z, Q, R, C, Z/mZ, 
        GF(p^n), number fields, a polynomial over Z, Q, Z/mZ, GF(p^n), 
        number fields, a rational function over Q or a matrix over all these 
        structures. 

        prod computes the product of exp for x=l to u (or @=l to u), the
        value of x (or @) at the end is u.
	If u<l, the result is 1.
              

        Example 1: (correct)

                prod(a=1,1000,a/(a+1))


        Example 2: (correct)

                prod(3,10,x+@)


        Example 3: (incorrect)

                prod(a=0,5,b=2*a)

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