Prepend
Details

- Prepend works on SparseArray objects, returning ordinary lists if necessary.
- Prepend can be used on Association objects. Single new elements are specified in the form key->value. New values replace older ones if their keys are the same.
- Multiple elements to prepend to an association can be specified in the form {key1->value1,key2->value2, …}.
- Prepend[elem][expr] is equivalent to Prepend[expr,elem].
Examples
open allclose allBasic Examples (3)Summary of the most common use cases
In[1]:=1

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https://wolfram.com/xid/0bn6byi-mm6
Out[1]=1

Prepend to an Association:
In[1]:=1

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https://wolfram.com/xid/0bn6byi-iovku2
Out[1]=1

Prepend several rules to an Association:
In[1]:=1

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https://wolfram.com/xid/0bn6byi-is8nxg
Out[1]=1

Generalizations & Extensions (1)Generalized and extended use cases
Applications (4)Sample problems that can be solved with this function
Possible Issues (1)Common pitfalls and unexpected behavior
In[1]:=1

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https://wolfram.com/xid/0bn6byi-luo
Out[1]=1

In[2]:=2

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https://wolfram.com/xid/0bn6byi-jbs
Out[2]=2

Wolfram Research (1988), Prepend, Wolfram Language function, https://reference.wolfram.com/language/ref/Prepend.html (updated 2014).
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Wolfram Research (1988), Prepend, Wolfram Language function, https://reference.wolfram.com/language/ref/Prepend.html (updated 2014).
Text
Wolfram Research (1988), Prepend, Wolfram Language function, https://reference.wolfram.com/language/ref/Prepend.html (updated 2014).
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Wolfram Research (1988), Prepend, Wolfram Language function, https://reference.wolfram.com/language/ref/Prepend.html (updated 2014).
CMS
Wolfram Language. 1988. "Prepend." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/Prepend.html.
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Wolfram Language. 1988. "Prepend." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2014. https://reference.wolfram.com/language/ref/Prepend.html.
APA
Wolfram Language. (1988). Prepend. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Prepend.html
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Wolfram Language. (1988). Prepend. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Prepend.html
BibTeX
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@misc{reference.wolfram_2025_prepend, author="Wolfram Research", title="{Prepend}", year="2014", howpublished="\url{https://reference.wolfram.com/language/ref/Prepend.html}", note=[Accessed: 10-July-2025
]}
BibLaTeX
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@online{reference.wolfram_2025_prepend, organization={Wolfram Research}, title={Prepend}, year={2014}, url={https://reference.wolfram.com/language/ref/Prepend.html}, note=[Accessed: 10-July-2025
]}