Number( list )
Number( list, func )
In the first form Number
returns the number of bound entries in the
list list.
For lists that contain no holes Number
, Length
(see Length), and
Size
(see Size) return the same value. For lists with holes Number
returns the number of bound entries, Length
returns the largest index
of a bound entry, and Size
signals an error.
Number
returns the number of elements of the list list for which the
unary function func returns true
. If an element for which func
returns true
appears several times in list it will also be counted
several times. func must return either true
or false
for every
element of list, otherwise an error is signalled.
gap> Number( [ 2, 3, 5, 7 ] ); 4 gap> Number( [, 2, 3,, 5,, 7,,,, 11 ] ); 5 gap> Number( [1..20], IsPrime ); 8 gap> Number( [ 1, 3, 4, -4, 4, 7, 10, 6 ], IsPrimePowerInt ); 4 gap> Number( [ 1, 3, 4, -4, 4, 7, 10, 6 ], > n -> IsPrimePowerInt(n) and n mod 2 <> 0 ); 2
Filtered
(see Filtered) allows you to extract the elements of a list
that have a certain property.
GAP 3.4.4