fold

Fold Vector Using Function

Fold a vector of symbolic variables using the power function. The output shows how fold combines elements of the vector from left to right by using the specified function.

syms a b c d e
fold(@power, [a b c d e])

ans =
(((a^b)^c)^d)^e

Assume Variable Belongs to Set of Values

Assume the variable x belongs to the set of values 1, 2, ..., 10 by applying or to the conditions x == 1, ..., x == 10 using fold. Check that the assumption is set by using assumptions.

syms x
cond = fold(@or, x == 1:10);
assume(cond)
assumptions

ans =
x == 1 | x == 2 | x == 3 | x == 4 | x == 5 |...
 x == 6 | x == 7 | x == 8 | x == 9 | x == 10

Specify Default Value of Fold Operation

Specify the default value of fold when the input is empty by specifying the third argument. If the third argument is not specified and the input is empty, then fold throws an error.

When creating a function to sum a vector, specify a default value of 0, such that the function returns 0 when the vector is empty.

sumVector = @(x) fold(@plus, x, 0);
sumVector([])

ans =
     0