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lib/trivial: Update function comments for doc generation

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Expands on some of the function comments and add some of the
special syntaxes recognised by nixdoc.
This commit is contained in:
Vincent Ambo 2018-10-27 16:40:04 +02:00
parent 8070a6333f
commit c2a744b9af
1 changed files with 87 additions and 30 deletions
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117
lib/trivial.nix
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@ -9,23 +9,37 @@ rec {
Type: id :: a -> a
*/
id = x: x;
id =
# The value to return
x: x;
/* The constant function
Ignores the second argument.
Or: Construct a function that always returns a static value.
Ignores the second argument. If called with only one argument,
constructs a function that always returns a static value.
Type: const :: a -> b -> a
Example:
let f = const 5; in f 10
=> 5
*/
const = x: y: x;
const =
# Value to return
x:
# Value to ignore
y: x;
## Named versions corresponding to some builtin operators.
/* Concatenate two lists */
/* Concatenate two lists
Type: concat :: [a] -> [a] -> [a]
Example:
concat [ 1 2 ] [ 3 4 ]
=> [ 1 2 3 4 ]
*/
concat = x: y: x ++ y;
/* boolean “or” */
@ -53,27 +67,40 @@ rec {
bitNot = builtins.sub (-1);
/* Convert a boolean to a string.
Note that toString on a bool returns "1" and "".
This function uses the strings "true" and "false" to represent
boolean values. Calling `toString` on a bool instead returns "1"
and "" (sic!).
Type: boolToString :: bool -> string
*/
boolToString = b: if b then "true" else "false";
/* Merge two attribute sets shallowly, right side trumps left
mergeAttrs :: attrs -> attrs -> attrs
Example:
mergeAttrs { a = 1; b = 2; } { b = 3; c = 4; }
=> { a = 1; b = 3; c = 4; }
*/
mergeAttrs = x: y: x // y;
mergeAttrs =
# Left attribute set
x:
# Right attribute set (higher precedence for equal keys)
y: x // y;
/* Flip the order of the arguments of a binary function.
Type: flip :: (a -> b -> c) -> (b -> a -> c)
Example:
flip concat [1] [2]
=> [ 2 1 ]
*/
flip = f: a: b: f b a;
/* Apply function if argument is non-null.
/* Apply function if the supplied argument is non-null.
Example:
mapNullable (x: x+1) null
@ -81,7 +108,11 @@ rec {
mapNullable (x: x+1) 22
=> 23
*/
mapNullable = f: a: if isNull a then a else f a;
mapNullable =
# Function to call
f:
# Argument to check for null before passing it to `f`
a: if isNull a then a else f a;
# Pull in some builtins not included elsewhere.
inherit (builtins)
@ -92,21 +123,27 @@ rec {
## nixpks version strings
# The current full nixpkgs version number.
/* Returns the current full nixpkgs version number. */
version = release + versionSuffix;
# The current nixpkgs version number as string.
/* Returns the current nixpkgs release number as string. */
release = lib.strings.fileContents ../.version;
# The current nixpkgs version suffix as string.
/* Returns the current nixpkgs version suffix as string. */
versionSuffix =
let suffixFile = ../.version-suffix;
in if pathExists suffixFile
then lib.strings.fileContents suffixFile
else "pre-git";
# Attempt to get the revision nixpkgs is from
revisionWithDefault = default:
/* Attempts to return the the current revision of nixpkgs and
returns the supplied default value otherwise.
Type: revisionWithDefault :: string -> string
*/
revisionWithDefault =
# Default value to return if revision can not be determined
default:
let
revisionFile = "${toString ./..}/.git-revision";
gitRepo = "${toString ./..}/.git";
@ -117,14 +154,20 @@ rec {
nixpkgsVersion = builtins.trace "`lib.nixpkgsVersion` is deprecated, use `lib.version` instead!" version;
# Whether we're being called by nix-shell.
/* Determine whether the function is being called from inside a Nix
shell.
Type: inNixShell :: bool
*/
inNixShell = builtins.getEnv "IN_NIX_SHELL" != "";
## Integer operations
# Return minimum/maximum of two numbers.
/* Return minimum of two numbers. */
min = x: y: if x < y then x else y;
/* Return maximum of two numbers. */
max = x: y: if x > y then x else y;
/* Integer modulus
@ -158,8 +201,9 @@ rec {
second subtype, compare elements of a single subtype with `yes`
and `no` respectively.
Example:
Type: (a -> bool) -> (a -> a -> int) -> (a -> a -> int) -> (a -> a -> int)
Example:
let cmp = splitByAndCompare (hasPrefix "foo") compare compare; in
cmp "a" "z" => -1
@ -170,31 +214,44 @@ rec {
# while
compare "fooa" "a" => 1
*/
splitByAndCompare = p: yes: no: a: b:
splitByAndCompare =
# Predicate
p:
# Comparison function if predicate holds for both values
yes:
# Comparison function if predicate holds for neither value
no:
# First value to compare
a:
# Second value to compare
b:
if p a
then if p b then yes a b else -1
else if p b then 1 else no a b;
/* Reads a JSON file. */
/* Reads a JSON file.
Type :: path -> any
*/
importJSON = path:
builtins.fromJSON (builtins.readFile path);
## Warnings
/* See https://github.com/NixOS/nix/issues/749. Eventually we'd like these
to expand to Nix builtins that carry metadata so that Nix can filter out
the INFO messages without parsing the message string.
# See https://github.com/NixOS/nix/issues/749. Eventually we'd like these
# to expand to Nix builtins that carry metadata so that Nix can filter out
# the INFO messages without parsing the message string.
#
# Usage:
# {
# foo = lib.warn "foo is deprecated" oldFoo;
# }
#
# TODO: figure out a clever way to integrate location information from
# something like __unsafeGetAttrPos.
Usage:
{
foo = lib.warn "foo is deprecated" oldFoo;
}
TODO: figure out a clever way to integrate location information from
something like __unsafeGetAttrPos.
*/
warn = msg: builtins.trace "WARNING: ${msg}";
info = msg: builtins.trace "INFO: ${msg}";