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# Description The "append" operator currently serves as both the append operator and the concatenation operator. This dual role creates ambiguity when operating on nested lists. ```nu [1 2] ++ 3 # appends a value to a list [1 2 3] [1 2] ++ [3 4] # concatenates two lists [1 2 3 4] [[1 2] [3 4]] ++ [5 6] # does this give [[1 2] [3 4] [5 6]] # or [[1 2] [3 4] 5 6] ``` Another problem is that `++=` can change the type of a variable: ```nu mut str = 'hello ' $str ++= ['world'] ($str | describe) == list<string> ``` Note that appending is only relevant for lists, but concatenation is relevant for lists, strings, and binary values. Additionally, appending can be expressed in terms of concatenation (see example below). So, this PR changes the `++` operator to only perform concatenation. # User-Facing Changes Using the `++` operator with a list and a non-list value will now be a compile time or runtime error. ```nu mut list = [] $list ++= 1 # error ``` Instead, concatenate a list with one element: ```nu $list ++= [1] ``` Or use `append`: ```nu $list = $list | append 1 ``` # After Submitting Update book and docs. --------- Co-authored-by: Douglas <32344964+NotTheDr01ds@users.noreply.github.com>
Nushell core libraries and plugins
These sub-crates form both the foundation for Nu and a set of plugins which extend Nu with additional functionality.
Foundational libraries are split into two kinds of crates:
- Core crates - those crates that work together to build the Nushell language engine
- Support crates - a set of crates that support the engine with additional features like JSON support, ANSI support, and more.
Plugins are likewise also split into two types:
- Core plugins - plugins that provide part of the default experience of Nu, including access to the system properties, processes, and web-connectivity features.
- Extra plugins - these plugins run a wide range of different capabilities like working with different file types, charting, viewing binary data, and more.