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Riffle[{e1,e2,…},x]

gives {e1,x,e2,x,…}.

Riffle[{e1,e2,…},{x1,x2,…}]

gives {e1,x1,e2,x2,…}.

Riffle[list,x,n]

yields a list in which every n^(th) element is x.

Riffle[list,x,{imin,imax,n}]

yields a list in which x appears if possible at positions imin, imin+n, imin+2n, … , imax.

Details
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Basic Examples  
Scope  
Applications  
Properties & Relations  
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Riffle

Riffle[{e1,e2,…},x]

gives {e1,x,e2,x,…}.

Riffle[{e1,e2,…},{x1,x2,…}]

gives {e1,x1,e2,x2,…}.

Riffle[list,x,n]

yields a list in which every n^(th) element is x.

Riffle[list,x,{imin,imax,n}]

yields a list in which x appears if possible at positions imin, imin+n, imin+2n, … , imax.

Details

  • If there are fewer xi than gaps between ei in Riffle[{e1,e2,…},{x1,x2,…}], the xi are used cyclically.
  • Riffle[{e},x] gives {e}.
  • The specification {imin,imax,n} is of the type used in Take. Negative indices count from the end of the list.
  • Riffle[list,x] is equivalent to Riffle[list,x,{2,-2,2}].
  • Riffle[list,x,n] is equivalent to Riffle[list,x,{n,-2,n}].
  • In Riffle[list,xlist], if list and xlist are of the same length, then their elements are directly interleaved, so that the last element of the result is the last element of xlist.
  • Riffle works with SparseArray objects.

Examples

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Basic Examples  (3)

Riffle x between successive elements in a list:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x]

Riffle in x and y cyclically:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, {x, y}]

Riffle in x at every 3^(rd) position:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x, 3]

Scope  (7)

Riffle in x at every other position:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x]
Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x, {2, -2, 2}]

Include x at the beginning and end:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x, {1, -1, 2}]

Use step 3:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x, {1, -1, 3}]

Start riffling in x only at position 5:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, x, {5, -1, 2}]

Cyclically riffle in x and y:

Wolfram Language code: Riffle[{1, 2, 3, 4, 5, 6, 7, 8, 9}, {x, y}, {5, -1, 2}]

Intersperse two lists:

Wolfram Language code: Riffle[{a, b, c, d}, {x, y, z, w}]

Riffle works on SparseArray objects:

Wolfram Language code: Riffle[SparseArray[5 -> 1, 10], x]

Applications  (5)

Insert spaces between words:

Wolfram Language code: StringJoin[Riffle[{"this", "is", "an", "example"}, " "]]

Create a directory name from a path list:

Wolfram Language code: StringJoin[Riffle[{"usr", "local", "bin"}, "/"]]

Insert 0s between successive integers:

Wolfram Language code: Riffle[Range[10], 0]

Alternate positive and negative integers:

Wolfram Language code: Riffle[Range[10], -Range[10]]

Insert commas at every 4^(th) character:

Wolfram Language code: StringJoin[Riffle[Characters["4345252523535"], ",", {-4, 1, -4}]]

Properties & Relations  (1)

Riffle is related to Transpose:

Wolfram Language code: Riffle[{a, b, c, d}, x]
Wolfram Language code: Flatten[Transpose[{{a, b, c, d}, {x, x, x, x}}]]
Wolfram Research (2007), Riffle, Wolfram Language function, https://reference.wolfram.com/language/ref/Riffle.html.

Text

Wolfram Research (2007), Riffle, Wolfram Language function, https://reference.wolfram.com/language/ref/Riffle.html.

CMS

Wolfram Language. 2007. "Riffle." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Riffle.html.

APA

Wolfram Language. (2007). Riffle. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Riffle.html

BibTeX

@misc{reference.wolfram_2026_riffle, author="Wolfram Research", title="{Riffle}", year="2007", howpublished="\url{https://reference.wolfram.com/language/ref/Riffle.html}", note=[Accessed: 13-June-2026]}

BibLaTeX

@online{reference.wolfram_2026_riffle, organization={Wolfram Research}, title={Riffle}, year={2007}, url={https://reference.wolfram.com/language/ref/Riffle.html}, note=[Accessed: 13-June-2026]}