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[nix/en] Updates for Nix 2.2.0

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- nix-repl now deprecated, Nix 2 has `nix repl`
- nix language now has floats, and type-preserving arithmetic
- add note about immutable sets' attributes being un-redefinable
- descendant sets can now have attributes added to them
- fix editing loose ene in the Impurity section
This commit is contained in:
Javier Candeira 2019-08-31 22:56:08 +10:00
parent 4e8e92eb0e
commit efcd37612d
1 changed files with 24 additions and 8 deletions
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@ -4,6 +4,7 @@ filename: learn.nix
contributors: contributors:
- ["Chris Martin", "http://chris-martin.org/"] - ["Chris Martin", "http://chris-martin.org/"]
- ["Rommel Martinez", "https://ebzzry.io"] - ["Rommel Martinez", "https://ebzzry.io"]
- ["Javier Candeira", "https://candeira.com/"]
--- ---
Nix is a simple functional language developed for the Nix is a simple functional language developed for the
@ -12,7 +13,7 @@ Nix is a simple functional language developed for the
You can evaluate Nix expressions using You can evaluate Nix expressions using
[nix-instantiate](https://nixos.org/nix/manual/#sec-nix-instantiate) [nix-instantiate](https://nixos.org/nix/manual/#sec-nix-instantiate)
or [`nix-repl`](https://github.com/edolstra/nix-repl). or [`nix repl`](https://nixos.org/nix/manual/#ssec-relnotes-2.0).
``` ```
with builtins; [ with builtins; [
@ -39,18 +40,26 @@ with builtins; [
#=> "a" #=> "a"
# Integers # Integers and Floats
#========================================= #=========================================
# Integers are the only numeric type. # There are two numeric types: integers and floats
1 0 42 (-3) # Some integers 1 0 42 (-3) # Some integers
123.43 .27e13 # A couple of floats
# Operations will preserve numeric type
(4 + 6 + 12 - 2) # Addition (4 + 6 + 12 - 2) # Addition
#=> 20 #=> 20
(4 - 2.5)
#=> 1.5
(7 / 2) # Division (7 / 2) # Division
#=> 3 #=> 3
(7 / 2.0)
#=> 3.5
# Strings # Strings
@ -238,13 +247,20 @@ with builtins; [
}.a.c }.a.c
#=> { d = 2; e = 3; } #=> { d = 2; e = 3; }
# An attribute's descendants cannot be assigned in this # Sets are immutable, so you can't redefine an attribute:
# way if the attribute itself has been directly assigned. {
a = { b = 1; };
a.b = 2;
}
#=> attribute 'a.b' at (string):3:5 already defined at (string):2:11
# However, an attribute's set members can also be defined piecewise
# way even if the attribute itself has been directly assigned.
{ {
a = { b = 1; }; a = { b = 1; };
a.c = 2; a.c = 2;
} }
#=> error: attribute ‘a’ already defined #=> { a = { b = 1; c = 2; }; }
# With # With
@ -321,8 +337,8 @@ with builtins; [
#========================================= #=========================================
# Because repeatability of builds is critical to the Nix package # Because repeatability of builds is critical to the Nix package
# manager, in which, functional purity is emphasized in the Nix # manager, functional purity is emphasized in the Nix language
# language. But there are a few impurities. # used to describe Nix packages. But there are a few impurities.
# You can refer to environment variables. # You can refer to environment variables.
(getEnv "HOME") (getEnv "HOME")