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Count : Counting Items

Count is a counter. Its internal value increases at each evaluation evaluated, if the input value is non nil.

Inputs and Outputs

Count has one default input and three outputs :

“what” : a value.
first output : triggers the increment of the counter if the input is non nil, and returns its current value.
second output : returns the current state of the counter.
third output : resets the value of the counter to zero.

Examples

Counting the Items of a List

Listloop returns each element of the list successively to count. These elements are non nil values.
The first output of count adds 1 every time listloop returns an element.
Once the enumeration of listloop is over, the final state of count is returned by Finally.

Counting Specific Items of a List

We will now apply count more specifically, to know how many strings a list contains among other types of items.

Listloop enumerates the elements of a list.
The stringp predicate returns true every time it evaluates a string.
At each step of the loop, the first output of count is evaluated :

* if it gets a non nil value from **stringp**, it increments the value of the counter
* if it gets "nil", the value doesn't change.   4. The results returned by **stringp** and counter are gathered in a list and printed.

The total number of strings, that is, the final state of counter is returned by Finally.

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