subtuple

Syntax

subtuple(X, range)

Arguments

X is a tuple of vectors with the same length.

range a pair of integers indicating a range. The lower bound is inclusive and the upper bound is exclusive.

Details

Create a read-only view of a subarray of each vector in X almost instantly. In contrast, it takes time to create a new tuple of vectors.

Examples

Example 1:

$ x=(1..10, 11..20, 21..30, 31..40)
$ subtuple(x, 2:4);
([3,4],[13,14],[23,24],[33,34])

Example 2

$ m=1000.0
$ n=20000000
$ a=(rand(m,n), rand(m,n))
$ k=10000000;
$ timer each(avg, a.subtuple(0:k));
Time elapsed: 30.87 ms

$ timer each(avg, (a[0][0:k], a[1][0:k]));
Time elapsed: 46.508 ms

Example 3. Subtuples are read-only.

$ x=(1..10, 11..20)
$ subtuple(x, 2:4)=([4, 5], [14, 15]);
Syntax Error: [line #2] Please use '==' rather than '=' as equal operator in non-sql expression.