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-- Status: rewritten July 2018
-- Author: Lily Silverstein
doc///
Key
number
Headline
count how many elements of a list satisfy a condition
Usage
number(A, f)
Inputs
A:
a list or sequence
f:
a boolean function
Outputs
c:
an integer, the number of elements of {\tt A} that satisfy {\tt f}
Description
Example
number(0..100, isPrime)
number(0..100, odd)
number(0..100, i -> i==17)
Text
To find the first or last index of an element satisfying the condition, see @TO position@.
For all indices that match the condition, see @TO positions@. To return the
elements, rather than their indices, see @TO select@.
Example
position((10,20,43,105,6), odd)
positions((10,20,43,105,6), odd)
select((10,20,43,105,6), odd)
SeeAlso
all
any
commonest
position
positions
same
select
tally
"lists and sequences"
///
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