Span

i;;j

represents a span of elements i through j.

i;;

represents a span from i to the end.

;;j

represents a span from the beginning to j.

;;

represents a span that includes all elements.

i;;j;;k

represents a span from i through j in steps of k.

i;;;;k

represents a span from i to the end in steps of k.

;;j;;k

represents a span from the beginning to j in steps of k.

;;;;k

represents a span from the beginning to the end in steps of k.

Details

  • m[[i;;j;;k]] is equivalent to Take[m,{i,j,k}].
  • m[[i;;j]]=v can be used to reset a span of elements in a list or other expression.
  • When used in Part, negative i and j count from the end.
  • In i;;j, i;;j;;k, etc., i and j can be of the form UpTo[n].
  • Any argument of Span[…] can be All, in which case it is interpreted as returning the largest possible number of elements consistent with any possible value of that argument.

Examples

open allclose all

Basic Examples  (3)

Take a span of elements from a list:

In[1]:=
Click for copyable input
Out[1]=

Take every third element:

In[1]:=
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Out[1]=

Assign to a span of elements:

In[1]:=
Click for copyable input
Out[1]=
In[2]:=
Click for copyable input
Out[2]=
In[3]:=
Click for copyable input
Out[3]=

Assign a sequence of different elements:

In[4]:=
Click for copyable input
Out[4]=
In[5]:=
Click for copyable input
Out[5]=

Scope  (7)

Properties & Relations  (4)

See Also

Take  Drop  Part  Range  Band

Introduced in 2007
(6.0)
| Updated in 2017
(11.2)