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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> |
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| src | ||
| std | ||
| tests | ||
| Cargo.toml | ||
| CONTRIBUTING.md | ||
| LICENSE | ||
| README.md | ||
| testing.nu | ||
Welcome to the standard library of `nushell`!
The standard library is a pure-nushell collection of custom commands which
provide interactive utilities and building blocks for users writing casual scripts or complex applications.
To see what's here:
> use std
> scope commands | select name description | where name =~ "std "
#┬───────────name────────────┬───────────────────description───────────────────
0│std assert │Universal assert command
1│std assert equal │Assert $left == $right
2│std assert error │Assert that executing the code generates an error
3│std assert greater │Assert $left > $right
4│std assert greater or equal│Assert $left >= $right
... ...
─┴───────────────────────────┴─────────────────────────────────────────────────
🧰 Using the standard library in the REPL or in scripts
All commands in the standard library must be "imported" into the running environment
(the interactive read-execute-print-loop (REPL) or a .nu script) using the
use command.
You can choose to import the whole module, but then must refer to individual commands with a std prefix, e.g:
use std
std log debug "Running now"
std assert (1 == 2)
Or you can enumerate the specific commands you want to import and invoke them without the std prefix.
use std ["log debug" assert]
log debug "Running again"
assert (2 == 1)
This is probably the form of import you'll want to add to your env.nu for interactive use.
✏️ contribute to the standard library
You're invited to contribute to the standard library! See CONTRIBUTING.md for details