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.
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Examples
Counting the Items of a List
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Listloop returns each element of the list successively to count. These elements are non nil values.
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The first output of count adds 1 every time listloop returns an element.
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Once the enumeration of listloop is over, the final state of count is returned by Finally.
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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.
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Listloop enumerates the elements of a list.
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The stringp predicate returns true every time it evaluates a string.
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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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