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Prepend

Status: Stable

documented, exercised by the test suite and/or worked examples, with no known limitations recorded.

Description

Prepend[expr, elem] adds elem to the beginning of expr.

Examples (2)

Every input below was run against the current Mathilda build and its output recorded.

Basic examples (2)

In[1]:= Append[<|"a" -> 1, "b" -> 2|>, "c" -> 3]
Out[1]= <|"a" -> 1, "b" -> 2, "c" -> 3|>

In[2]:= Append[<|"a" -> 1|>, "a" -> 99]
Out[2]= <|"a" -> 99|>

Implementation notes

Algorithm. builtin_prepend builds a new function node with the same head whose first element is a copy of the new element followed by copies of all original arguments. Two-argument form only; returns NULL if the first argument is an atom. (PrependTo is the mutating variant that writes the result back to a symbol's OwnValue.)

Attributes: none registered.

References

See also: Append, AssociateTo