fold function:

Fold all the items in a list into a new value. The first item should be the list, the second one the initial value and the third one a function that create the fold. If the fuinction has only two arguments, the initial value will not be set. The function will accespt as input an hash with value, index and so_far keys (if the previous run returned nothing, the so_far will be empty).

Examples:

• running: (fold [1, 10, 0.6], 100, (+ .index .so_far .value)) will give: 114.6 Because the first argument is 100, and then the fold will add all the argument in the list, 100 + 1 + 10 + 0.6 = 114.6.

• running: (fold [1, 10, 0.6], (? (number? .so_far) (+ .so_far .value) .value)) will give: 11.6 Because if so_far is not a number, we started the fold, so we can return the value, hene this is a simple sum, 1 + 10 + 0.6 = 11.6.

• running: (fold {}, 1, 2) will return nothing