Glossary

• Enumerables - A set of methods that traverse or sort collections (ranges, arrays, hashes).

Enumerable Methods

• all? - Passes each element in its receiver to a given block; returns true if the block never returns a falsey value (otherwise it returns false).
• any? - Passes each element in its receiver to a given block; returns true if the block ever returns a truthy value (otherwise it returns false).
• count - With no arguments: returns the number of elements in its receiver; with one argument: returns the number of elements in its receiver equal to its argument; with a block: returns the number of items in its receiver that, when passed to the block, return a truthy value.
• each_with_index - Calls the given block with two arguments--the item and the item's index--once for each element in the method's receiver.
• map - Returns a new array that's the result of executing its given block once for each element in its receiver.
• none? - Passes each element in its receiver to a given block; returns true if the block never returns a truthy value (otherwise it returns false).
• reduce - Combines all elements of its receiver by applying a binary operation, specified by a block or a symbol that names a method or operator; synonymous with inject.
• reject - Returns a collection containing all the elements in its receiver for which the given block returns a falsey value.
• select - Returns a collection containing all the elements in its receiver for which the given block returns a truthy value.
• sort_by - Sorts its receiver by the return values of its elements when they are passed to the given block and returns an array in that order.
• with_index - A chainable method that allows the block given to map or each_char to receive indices as well as receiver elements.