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MaxBy    --    a maximum element of a list


Syntax 
MaxBy(L: LIST, LessThanFunc: FUNCTION)

Description
This function returns a maximum of the elements of the list L with respect to the comparisons made by LessThanFunc.

The comparison function LessThanFunc takes two arguments and returns true if the first argument is less than the second, otherwise it returns false.

NOTE: to call MaxBy(L,LessThanFunc) inside a function you will need to make the name LessThanFunc accessible using TopLevel LessThanFunc;

NOTE: if both LessThanFunc(A, B) and LessThanFunc(B, A) return true, then A and B are viewed as being equal: for example, when comparing two polynomials by their LPP only.

Example 
/**/  Define ByLength(S, T)    -- define the sorting function
/**/    Return len(S) < len(T);
/**/  EndDefine;

/**/  L := ["bird", "mouse", "cat", "elephant"];
/**/  MaxBy(L, ByLength);
elephant

/**/  use QQ[x,y];
/**/  Define ByLPP(S, T)  return LPP(S) < LPP(T);  EndDefine;
/**/  L := [x^2*y -y -3, x^5 -1, x^5 -y^2 +3];
/**/  MaxBy(L, ByLPP);
x^5 -1

See Also