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nixpkgs-immich/lib/strings.nix
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immich sync
2024-09-17 10:23:40 -06:00

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/**
String manipulation functions.
*/
{ lib }:
let
inherit (builtins) length;
inherit (lib.trivial) warnIf;
asciiTable = import ./ascii-table.nix;
in
rec {
inherit (builtins)
compareVersions
elem
elemAt
filter
fromJSON
genList
head
isInt
isList
isAttrs
isPath
isString
match
parseDrvName
readFile
replaceStrings
split
storeDir
stringLength
substring
tail
toJSON
typeOf
unsafeDiscardStringContext
;
/**
Concatenate a list of strings.
# Type
```
concatStrings :: [string] -> string
```
# Examples
:::{.example}
## `lib.strings.concatStrings` usage example
```nix
concatStrings ["foo" "bar"]
=> "foobar"
```
:::
*/
concatStrings = builtins.concatStringsSep "";
/**
Map a function over a list and concatenate the resulting strings.
# Inputs
`f`
: 1\. Function argument
`list`
: 2\. Function argument
# Type
```
concatMapStrings :: (a -> string) -> [a] -> string
```
# Examples
:::{.example}
## `lib.strings.concatMapStrings` usage example
```nix
concatMapStrings (x: "a" + x) ["foo" "bar"]
=> "afooabar"
```
:::
*/
concatMapStrings = f: list: concatStrings (map f list);
/**
Like `concatMapStrings` except that the f functions also gets the
position as a parameter.
# Inputs
`f`
: 1\. Function argument
`list`
: 2\. Function argument
# Type
```
concatImapStrings :: (int -> a -> string) -> [a] -> string
```
# Examples
:::{.example}
## `lib.strings.concatImapStrings` usage example
```nix
concatImapStrings (pos: x: "${toString pos}-${x}") ["foo" "bar"]
=> "1-foo2-bar"
```
:::
*/
concatImapStrings = f: list: concatStrings (lib.imap1 f list);
/**
Place an element between each element of a list
# Inputs
`separator`
: Separator to add between elements
`list`
: Input list
# Type
```
intersperse :: a -> [a] -> [a]
```
# Examples
:::{.example}
## `lib.strings.intersperse` usage example
```nix
intersperse "/" ["usr" "local" "bin"]
=> ["usr" "/" "local" "/" "bin"].
```
:::
*/
intersperse =
separator:
list:
if list == [] || length list == 1
then list
else tail (lib.concatMap (x: [separator x]) list);
/**
Concatenate a list of strings with a separator between each element
# Inputs
`sep`
: Separator to add between elements
`list`
: List of input strings
# Type
```
concatStringsSep :: string -> [string] -> string
```
# Examples
:::{.example}
## `lib.strings.concatStringsSep` usage example
```nix
concatStringsSep "/" ["usr" "local" "bin"]
=> "usr/local/bin"
```
:::
*/
concatStringsSep = builtins.concatStringsSep;
/**
Maps a function over a list of strings and then concatenates the
result with the specified separator interspersed between
elements.
# Inputs
`sep`
: Separator to add between elements
`f`
: Function to map over the list
`list`
: List of input strings
# Type
```
concatMapStringsSep :: string -> (a -> string) -> [a] -> string
```
# Examples
:::{.example}
## `lib.strings.concatMapStringsSep` usage example
```nix
concatMapStringsSep "-" (x: toUpper x) ["foo" "bar" "baz"]
=> "FOO-BAR-BAZ"
```
:::
*/
concatMapStringsSep =
sep:
f:
list: concatStringsSep sep (map f list);
/**
Same as `concatMapStringsSep`, but the mapping function
additionally receives the position of its argument.
# Inputs
`sep`
: Separator to add between elements
`f`
: Function that receives elements and their positions
`list`
: List of input strings
# Type
```
concatIMapStringsSep :: string -> (int -> a -> string) -> [a] -> string
```
# Examples
:::{.example}
## `lib.strings.concatImapStringsSep` usage example
```nix
concatImapStringsSep "-" (pos: x: toString (x / pos)) [ 6 6 6 ]
=> "6-3-2"
```
:::
*/
concatImapStringsSep =
sep:
f:
list: concatStringsSep sep (lib.imap1 f list);
/**
Concatenate a list of strings, adding a newline at the end of each one.
Defined as `concatMapStrings (s: s + "\n")`.
# Inputs
`list`
: List of strings. Any element that is not a string will be implicitly converted to a string.
# Type
```
concatLines :: [string] -> string
```
# Examples
:::{.example}
## `lib.strings.concatLines` usage example
```nix
concatLines [ "foo" "bar" ]
=> "foo\nbar\n"
```
:::
*/
concatLines = concatMapStrings (s: s + "\n");
/**
Repeat a string `n` times,
and concatenate the parts into a new string.
# Inputs
`n`
: 1\. Function argument
`s`
: 2\. Function argument
# Type
```
replicate :: int -> string -> string
```
# Examples
:::{.example}
## `lib.strings.replicate` usage example
```nix
replicate 3 "v"
=> "vvv"
replicate 5 "hello"
=> "hellohellohellohellohello"
```
:::
*/
replicate = n: s: concatStrings (lib.lists.replicate n s);
/**
Remove leading and trailing whitespace from a string `s`.
Whitespace is defined as any of the following characters:
" ", "\t" "\r" "\n"
# Inputs
`s`
: The string to trim
# Type
```
trim :: string -> string
```
# Examples
:::{.example}
## `lib.strings.trim` usage example
```nix
trim " hello, world! "
=> "hello, world!"
```
:::
*/
trim = trimWith {
start = true;
end = true;
};
/**
Remove leading and/or trailing whitespace from a string `s`.
To remove both leading and trailing whitespace, you can also use [`trim`](#function-library-lib.strings.trim)
Whitespace is defined as any of the following characters:
" ", "\t" "\r" "\n"
# Inputs
`config` (Attribute set)
: `start`
: Whether to trim leading whitespace (`false` by default)
: `end`
: Whether to trim trailing whitespace (`false` by default)
`s`
: The string to trim
# Type
```
trimWith :: { start :: Bool; end :: Bool } -> String -> String
```
# Examples
:::{.example}
## `lib.strings.trimWith` usage example
```nix
trimWith { start = true; } " hello, world! "}
=> "hello, world! "
trimWith { end = true; } " hello, world! "}
=> " hello, world!"
```
:::
*/
trimWith =
{
start ? false,
end ? false,
}:
s:
let
# Define our own whitespace character class instead of using
# `[:space:]`, which is not well-defined.
chars = " \t\r\n";
# To match up until trailing whitespace, we need to capture a
# group that ends with a non-whitespace character.
regex =
if start && end then
"[${chars}]*(.*[^${chars}])[${chars}]*"
else if start then
"[${chars}]*(.*)"
else if end then
"(.*[^${chars}])[${chars}]*"
else
"(.*)";
# If the string was empty or entirely whitespace,
# then the regex may not match and `res` will be `null`.
res = match regex s;
in
optionalString (res != null) (head res);
/**
Construct a Unix-style, colon-separated search path consisting of
the given `subDir` appended to each of the given paths.
# Inputs
`subDir`
: Directory name to append
`paths`
: List of base paths
# Type
```
makeSearchPath :: string -> [string] -> string
```
# Examples
:::{.example}
## `lib.strings.makeSearchPath` usage example
```nix
makeSearchPath "bin" ["/root" "/usr" "/usr/local"]
=> "/root/bin:/usr/bin:/usr/local/bin"
makeSearchPath "bin" [""]
=> "/bin"
```
:::
*/
makeSearchPath =
subDir:
paths:
concatStringsSep ":" (map (path: path + "/" + subDir) (filter (x: x != null) paths));
/**
Construct a Unix-style search path by appending the given
`subDir` to the specified `output` of each of the packages.
If no output by the given name is found, fallback to `.out` and then to
the default.
# Inputs
`output`
: Package output to use
`subDir`
: Directory name to append
`pkgs`
: List of packages
# Type
```
makeSearchPathOutput :: string -> string -> [package] -> string
```
# Examples
:::{.example}
## `lib.strings.makeSearchPathOutput` usage example
```nix
makeSearchPathOutput "dev" "bin" [ pkgs.openssl pkgs.zlib ]
=> "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r-dev/bin:/nix/store/wwh7mhwh269sfjkm6k5665b5kgp7jrk2-zlib-1.2.8/bin"
```
:::
*/
makeSearchPathOutput =
output:
subDir:
pkgs: makeSearchPath subDir (map (lib.getOutput output) pkgs);
/**
Construct a library search path (such as RPATH) containing the
libraries for a set of packages
# Inputs
`packages`
: List of packages
# Type
```
makeLibraryPath :: [package] -> string
```
# Examples
:::{.example}
## `lib.strings.makeLibraryPath` usage example
```nix
makeLibraryPath [ "/usr" "/usr/local" ]
=> "/usr/lib:/usr/local/lib"
pkgs = import <nixpkgs> { }
makeLibraryPath [ pkgs.openssl pkgs.zlib ]
=> "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r/lib:/nix/store/wwh7mhwh269sfjkm6k5665b5kgp7jrk2-zlib-1.2.8/lib"
```
:::
*/
makeLibraryPath = makeSearchPathOutput "lib" "lib";
/**
Construct an include search path (such as C_INCLUDE_PATH) containing the
header files for a set of packages or paths.
# Inputs
`packages`
: List of packages
# Type
```
makeIncludePath :: [package] -> string
```
# Examples
:::{.example}
## `lib.strings.makeIncludePath` usage example
```nix
makeIncludePath [ "/usr" "/usr/local" ]
=> "/usr/include:/usr/local/include"
pkgs = import <nixpkgs> { }
makeIncludePath [ pkgs.openssl pkgs.zlib ]
=> "/nix/store/9rz8gxhzf8sw4kf2j2f1grr49w8zx5vj-openssl-1.0.1r-dev/include:/nix/store/wwh7mhwh269sfjkm6k5665b5kgp7jrk2-zlib-1.2.8-dev/include"
```
:::
*/
makeIncludePath = makeSearchPathOutput "dev" "include";
/**
Construct a binary search path (such as $PATH) containing the
binaries for a set of packages.
# Inputs
`packages`
: List of packages
# Type
```
makeBinPath :: [package] -> string
```
# Examples
:::{.example}
## `lib.strings.makeBinPath` usage example
```nix
makeBinPath ["/root" "/usr" "/usr/local"]
=> "/root/bin:/usr/bin:/usr/local/bin"
```
:::
*/
makeBinPath = makeSearchPathOutput "bin" "bin";
/**
Normalize path, removing extraneous /s
# Inputs
`s`
: 1\. Function argument
# Type
```
normalizePath :: string -> string
```
# Examples
:::{.example}
## `lib.strings.normalizePath` usage example
```nix
normalizePath "/a//b///c/"
=> "/a/b/c/"
```
:::
*/
normalizePath = s:
warnIf
(isPath s)
''
lib.strings.normalizePath: The argument (${toString s}) is a path value, but only strings are supported.
Path values are always normalised in Nix, so there's no need to call this function on them.
This function also copies the path to the Nix store and returns the store path, the same as "''${path}" will, which may not be what you want.
This behavior is deprecated and will throw an error in the future.''
(
builtins.foldl'
(x: y: if y == "/" && hasSuffix "/" x then x else x+y)
""
(stringToCharacters s)
);
/**
Depending on the boolean `cond', return either the given string
or the empty string. Useful to concatenate against a bigger string.
# Inputs
`cond`
: Condition
`string`
: String to return if condition is true
# Type
```
optionalString :: bool -> string -> string
```
# Examples
:::{.example}
## `lib.strings.optionalString` usage example
```nix
optionalString true "some-string"
=> "some-string"
optionalString false "some-string"
=> ""
```
:::
*/
optionalString =
cond:
string: if cond then string else "";
/**
Determine whether a string has given prefix.
# Inputs
`pref`
: Prefix to check for
`str`
: Input string
# Type
```
hasPrefix :: string -> string -> bool
```
# Examples
:::{.example}
## `lib.strings.hasPrefix` usage example
```nix
hasPrefix "foo" "foobar"
=> true
hasPrefix "foo" "barfoo"
=> false
```
:::
*/
hasPrefix =
pref:
str:
# Before 23.05, paths would be copied to the store before converting them
# to strings and comparing. This was surprising and confusing.
warnIf
(isPath pref)
''
lib.strings.hasPrefix: The first argument (${toString pref}) is a path value, but only strings are supported.
There is almost certainly a bug in the calling code, since this function always returns `false` in such a case.
This function also copies the path to the Nix store, which may not be what you want.
This behavior is deprecated and will throw an error in the future.
You might want to use `lib.path.hasPrefix` instead, which correctly supports paths.''
(substring 0 (stringLength pref) str == pref);
/**
Determine whether a string has given suffix.
# Inputs
`suffix`
: Suffix to check for
`content`
: Input string
# Type
```
hasSuffix :: string -> string -> bool
```
# Examples
:::{.example}
## `lib.strings.hasSuffix` usage example
```nix
hasSuffix "foo" "foobar"
=> false
hasSuffix "foo" "barfoo"
=> true
```
:::
*/
hasSuffix =
suffix:
content:
let
lenContent = stringLength content;
lenSuffix = stringLength suffix;
in
# Before 23.05, paths would be copied to the store before converting them
# to strings and comparing. This was surprising and confusing.
warnIf
(isPath suffix)
''
lib.strings.hasSuffix: The first argument (${toString suffix}) is a path value, but only strings are supported.
There is almost certainly a bug in the calling code, since this function always returns `false` in such a case.
This function also copies the path to the Nix store, which may not be what you want.
This behavior is deprecated and will throw an error in the future.''
(
lenContent >= lenSuffix
&& substring (lenContent - lenSuffix) lenContent content == suffix
);
/**
Determine whether a string contains the given infix
# Inputs
`infix`
: 1\. Function argument
`content`
: 2\. Function argument
# Type
```
hasInfix :: string -> string -> bool
```
# Examples
:::{.example}
## `lib.strings.hasInfix` usage example
```nix
hasInfix "bc" "abcd"
=> true
hasInfix "ab" "abcd"
=> true
hasInfix "cd" "abcd"
=> true
hasInfix "foo" "abcd"
=> false
```
:::
*/
hasInfix = infix: content:
# Before 23.05, paths would be copied to the store before converting them
# to strings and comparing. This was surprising and confusing.
warnIf
(isPath infix)
''
lib.strings.hasInfix: The first argument (${toString infix}) is a path value, but only strings are supported.
There is almost certainly a bug in the calling code, since this function always returns `false` in such a case.
This function also copies the path to the Nix store, which may not be what you want.
This behavior is deprecated and will throw an error in the future.''
(builtins.match ".*${escapeRegex infix}.*" "${content}" != null);
/**
Convert a string `s` to a list of characters (i.e. singleton strings).
This allows you to, e.g., map a function over each character. However,
note that this will likely be horribly inefficient; Nix is not a
general purpose programming language. Complex string manipulations
should, if appropriate, be done in a derivation.
Also note that Nix treats strings as a list of bytes and thus doesn't
handle unicode.
# Inputs
`s`
: 1\. Function argument
# Type
```
stringToCharacters :: string -> [string]
```
# Examples
:::{.example}
## `lib.strings.stringToCharacters` usage example
```nix
stringToCharacters ""
=> [ ]
stringToCharacters "abc"
=> [ "a" "b" "c" ]
stringToCharacters "🦄"
=> [ "<EFBFBD>" "<EFBFBD>" "<EFBFBD>" "<EFBFBD>" ]
```
:::
*/
stringToCharacters = s:
genList (p: substring p 1 s) (stringLength s);
/**
Manipulate a string character by character and replace them by
strings before concatenating the results.
# Inputs
`f`
: Function to map over each individual character
`s`
: Input string
# Type
```
stringAsChars :: (string -> string) -> string -> string
```
# Examples
:::{.example}
## `lib.strings.stringAsChars` usage example
```nix
stringAsChars (x: if x == "a" then "i" else x) "nax"
=> "nix"
```
:::
*/
stringAsChars =
# Function to map over each individual character
f:
# Input string
s: concatStrings (
map f (stringToCharacters s)
);
/**
Convert char to ascii value, must be in printable range
# Inputs
`c`
: 1\. Function argument
# Type
```
charToInt :: string -> int
```
# Examples
:::{.example}
## `lib.strings.charToInt` usage example
```nix
charToInt "A"
=> 65
charToInt "("
=> 40
```
:::
*/
charToInt = c: builtins.getAttr c asciiTable;
/**
Escape occurrence of the elements of `list` in `string` by
prefixing it with a backslash.
# Inputs
`list`
: 1\. Function argument
`string`
: 2\. Function argument
# Type
```
escape :: [string] -> string -> string
```
# Examples
:::{.example}
## `lib.strings.escape` usage example
```nix
escape ["(" ")"] "(foo)"
=> "\\(foo\\)"
```
:::
*/
escape = list: replaceStrings list (map (c: "\\${c}") list);
/**
Escape occurrence of the element of `list` in `string` by
converting to its ASCII value and prefixing it with \\x.
Only works for printable ascii characters.
# Inputs
`list`
: 1\. Function argument
`string`
: 2\. Function argument
# Type
```
escapeC = [string] -> string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeC` usage example
```nix
escapeC [" "] "foo bar"
=> "foo\\x20bar"
```
:::
*/
escapeC = list: replaceStrings list (map (c: "\\x${ toLower (lib.toHexString (charToInt c))}") list);
/**
Escape the `string` so it can be safely placed inside a URL
query.
# Inputs
`string`
: 1\. Function argument
# Type
```
escapeURL :: string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeURL` usage example
```nix
escapeURL "foo/bar baz"
=> "foo%2Fbar%20baz"
```
:::
*/
escapeURL = let
unreserved = [ "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z" "0" "1" "2" "3" "4" "5" "6" "7" "8" "9" "-" "_" "." "~" ];
toEscape = builtins.removeAttrs asciiTable unreserved;
in
replaceStrings (builtins.attrNames toEscape) (lib.mapAttrsToList (_: c: "%${fixedWidthString 2 "0" (lib.toHexString c)}") toEscape);
/**
Quote `string` to be used safely within the Bourne shell.
# Inputs
`string`
: 1\. Function argument
# Type
```
escapeShellArg :: string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeShellArg` usage example
```nix
escapeShellArg "esc'ape\nme"
=> "'esc'\\''ape\nme'"
```
:::
*/
escapeShellArg = arg: "'${replaceStrings ["'"] ["'\\''"] (toString arg)}'";
/**
Quote all arguments to be safely passed to the Bourne shell.
# Inputs
`args`
: 1\. Function argument
# Type
```
escapeShellArgs :: [string] -> string
```
# Examples
:::{.example}
## `lib.strings.escapeShellArgs` usage example
```nix
escapeShellArgs ["one" "two three" "four'five"]
=> "'one' 'two three' 'four'\\''five'"
```
:::
*/
escapeShellArgs = concatMapStringsSep " " escapeShellArg;
/**
Test whether the given `name` is a valid POSIX shell variable name.
# Inputs
`name`
: 1\. Function argument
# Type
```
string -> bool
```
# Examples
:::{.example}
## `lib.strings.isValidPosixName` usage example
```nix
isValidPosixName "foo_bar000"
=> true
isValidPosixName "0-bad.jpg"
=> false
```
:::
*/
isValidPosixName = name: match "[a-zA-Z_][a-zA-Z0-9_]*" name != null;
/**
Translate a Nix value into a shell variable declaration, with proper escaping.
The value can be a string (mapped to a regular variable), a list of strings
(mapped to a Bash-style array) or an attribute set of strings (mapped to a
Bash-style associative array). Note that "string" includes string-coercible
values like paths or derivations.
Strings are translated into POSIX sh-compatible code; lists and attribute sets
assume a shell that understands Bash syntax (e.g. Bash or ZSH).
# Inputs
`name`
: 1\. Function argument
`value`
: 2\. Function argument
# Type
```
string -> ( string | [string] | { ${name} :: string; } ) -> string
```
# Examples
:::{.example}
## `lib.strings.toShellVar` usage example
```nix
''
${toShellVar "foo" "some string"}
[[ "$foo" == "some string" ]]
''
```
:::
*/
toShellVar = name: value:
lib.throwIfNot (isValidPosixName name) "toShellVar: ${name} is not a valid shell variable name" (
if isAttrs value && ! isStringLike value then
"declare -A ${name}=(${
concatStringsSep " " (lib.mapAttrsToList (n: v:
"[${escapeShellArg n}]=${escapeShellArg v}"
) value)
})"
else if isList value then
"declare -a ${name}=(${escapeShellArgs value})"
else
"${name}=${escapeShellArg value}"
);
/**
Translate an attribute set `vars` into corresponding shell variable declarations
using `toShellVar`.
# Inputs
`vars`
: 1\. Function argument
# Type
```
toShellVars :: {
${name} :: string | [ string ] | { ${key} :: string; };
} -> string
```
# Examples
:::{.example}
## `lib.strings.toShellVars` usage example
```nix
let
foo = "value";
bar = foo;
in ''
${toShellVars { inherit foo bar; }}
[[ "$foo" == "$bar" ]]
''
```
:::
*/
toShellVars = vars: concatStringsSep "\n" (lib.mapAttrsToList toShellVar vars);
/**
Turn a string `s` into a Nix expression representing that string
# Inputs
`s`
: 1\. Function argument
# Type
```
escapeNixString :: string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeNixString` usage example
```nix
escapeNixString "hello\${}\n"
=> "\"hello\\\${}\\n\""
```
:::
*/
escapeNixString = s: escape ["$"] (toJSON s);
/**
Turn a string `s` into an exact regular expression
# Inputs
`s`
: 1\. Function argument
# Type
```
escapeRegex :: string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeRegex` usage example
```nix
escapeRegex "[^a-z]*"
=> "\\[\\^a-z]\\*"
```
:::
*/
escapeRegex = escape (stringToCharacters "\\[{()^$?*+|.");
/**
Quotes a string `s` if it can't be used as an identifier directly.
# Inputs
`s`
: 1\. Function argument
# Type
```
escapeNixIdentifier :: string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeNixIdentifier` usage example
```nix
escapeNixIdentifier "hello"
=> "hello"
escapeNixIdentifier "0abc"
=> "\"0abc\""
```
:::
*/
escapeNixIdentifier = s:
# Regex from https://github.com/NixOS/nix/blob/d048577909e383439c2549e849c5c2f2016c997e/src/libexpr/lexer.l#L91
if match "[a-zA-Z_][a-zA-Z0-9_'-]*" s != null
then s else escapeNixString s;
/**
Escapes a string `s` such that it is safe to include verbatim in an XML
document.
# Inputs
`s`
: 1\. Function argument
# Type
```
escapeXML :: string -> string
```
# Examples
:::{.example}
## `lib.strings.escapeXML` usage example
```nix
escapeXML ''"test" 'test' < & >''
=> "&quot;test&quot; &apos;test&apos; &lt; &amp; &gt;"
```
:::
*/
escapeXML = builtins.replaceStrings
["\"" "'" "<" ">" "&"]
["&quot;" "&apos;" "&lt;" "&gt;" "&amp;"];
# warning added 12-12-2022
replaceChars = lib.warn "lib.replaceChars is a deprecated alias of lib.replaceStrings." builtins.replaceStrings;
# Case conversion utilities.
lowerChars = stringToCharacters "abcdefghijklmnopqrstuvwxyz";
upperChars = stringToCharacters "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
/**
Converts an ASCII string `s` to lower-case.
# Inputs
`s`
: The string to convert to lower-case.
# Type
```
toLower :: string -> string
```
# Examples
:::{.example}
## `lib.strings.toLower` usage example
```nix
toLower "HOME"
=> "home"
```
:::
*/
toLower = replaceStrings upperChars lowerChars;
/**
Converts an ASCII string `s` to upper-case.
# Inputs
`s`
: The string to convert to upper-case.
# Type
```
toUpper :: string -> string
```
# Examples
:::{.example}
## `lib.strings.toUpper` usage example
```nix
toUpper "home"
=> "HOME"
```
:::
*/
toUpper = replaceStrings lowerChars upperChars;
/**
Appends string context from string like object `src` to `target`.
:::{.warning}
This is an implementation
detail of Nix and should be used carefully.
:::
Strings in Nix carry an invisible `context` which is a list of strings
representing store paths. If the string is later used in a derivation
attribute, the derivation will properly populate the inputDrvs and
inputSrcs.
# Inputs
`src`
: The string to take the context from. If the argument is not a string,
it will be implicitly converted to a string.
`target`
: The string to append the context to. If the argument is not a string,
it will be implicitly converted to a string.
# Type
```
addContextFrom :: string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.addContextFrom` usage example
```nix
pkgs = import <nixpkgs> { };
addContextFrom pkgs.coreutils "bar"
=> "bar"
```
The context can be displayed using the `toString` function:
```nix
nix-repl> builtins.getContext (lib.strings.addContextFrom pkgs.coreutils "bar")
{
"/nix/store/m1s1d2dk2dqqlw3j90jl3cjy2cykbdxz-coreutils-9.5.drv" = { ... };
}
```
:::
*/
addContextFrom = src: target: substring 0 0 src + target;
/**
Cut a string with a separator and produces a list of strings which
were separated by this separator.
# Inputs
`sep`
: 1\. Function argument
`s`
: 2\. Function argument
# Type
```
splitString :: string -> string -> [string]
```
# Examples
:::{.example}
## `lib.strings.splitString` usage example
```nix
splitString "." "foo.bar.baz"
=> [ "foo" "bar" "baz" ]
splitString "/" "/usr/local/bin"
=> [ "" "usr" "local" "bin" ]
```
:::
*/
splitString = sep: s:
let
splits = builtins.filter builtins.isString (builtins.split (escapeRegex (toString sep)) (toString s));
in
map (addContextFrom s) splits;
/**
Return a string without the specified prefix, if the prefix matches.
# Inputs
`prefix`
: Prefix to remove if it matches
`str`
: Input string
# Type
```
removePrefix :: string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.removePrefix` usage example
```nix
removePrefix "foo." "foo.bar.baz"
=> "bar.baz"
removePrefix "xxx" "foo.bar.baz"
=> "foo.bar.baz"
```
:::
*/
removePrefix =
prefix:
str:
# Before 23.05, paths would be copied to the store before converting them
# to strings and comparing. This was surprising and confusing.
warnIf
(isPath prefix)
''
lib.strings.removePrefix: The first argument (${toString prefix}) is a path value, but only strings are supported.
There is almost certainly a bug in the calling code, since this function never removes any prefix in such a case.
This function also copies the path to the Nix store, which may not be what you want.
This behavior is deprecated and will throw an error in the future.''
(let
preLen = stringLength prefix;
in
if substring 0 preLen str == prefix then
# -1 will take the string until the end
substring preLen (-1) str
else
str);
/**
Return a string without the specified suffix, if the suffix matches.
# Inputs
`suffix`
: Suffix to remove if it matches
`str`
: Input string
# Type
```
removeSuffix :: string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.removeSuffix` usage example
```nix
removeSuffix "front" "homefront"
=> "home"
removeSuffix "xxx" "homefront"
=> "homefront"
```
:::
*/
removeSuffix =
suffix:
str:
# Before 23.05, paths would be copied to the store before converting them
# to strings and comparing. This was surprising and confusing.
warnIf
(isPath suffix)
''
lib.strings.removeSuffix: The first argument (${toString suffix}) is a path value, but only strings are supported.
There is almost certainly a bug in the calling code, since this function never removes any suffix in such a case.
This function also copies the path to the Nix store, which may not be what you want.
This behavior is deprecated and will throw an error in the future.''
(let
sufLen = stringLength suffix;
sLen = stringLength str;
in
if sufLen <= sLen && suffix == substring (sLen - sufLen) sufLen str then
substring 0 (sLen - sufLen) str
else
str);
/**
Return true if string `v1` denotes a version older than `v2`.
# Inputs
`v1`
: 1\. Function argument
`v2`
: 2\. Function argument
# Type
```
versionOlder :: String -> String -> Bool
```
# Examples
:::{.example}
## `lib.strings.versionOlder` usage example
```nix
versionOlder "1.1" "1.2"
=> true
versionOlder "1.1" "1.1"
=> false
```
:::
*/
versionOlder = v1: v2: compareVersions v2 v1 == 1;
/**
Return true if string v1 denotes a version equal to or newer than v2.
# Inputs
`v1`
: 1\. Function argument
`v2`
: 2\. Function argument
# Type
```
versionAtLeast :: String -> String -> Bool
```
# Examples
:::{.example}
## `lib.strings.versionAtLeast` usage example
```nix
versionAtLeast "1.1" "1.0"
=> true
versionAtLeast "1.1" "1.1"
=> true
versionAtLeast "1.1" "1.2"
=> false
```
:::
*/
versionAtLeast = v1: v2: !versionOlder v1 v2;
/**
This function takes an argument `x` that's either a derivation or a
derivation's "name" attribute and extracts the name part from that
argument.
# Inputs
`x`
: 1\. Function argument
# Type
```
getName :: String | Derivation -> String
```
# Examples
:::{.example}
## `lib.strings.getName` usage example
```nix
getName "youtube-dl-2016.01.01"
=> "youtube-dl"
getName pkgs.youtube-dl
=> "youtube-dl"
```
:::
*/
getName = let
parse = drv: (parseDrvName drv).name;
in x:
if isString x
then parse x
else x.pname or (parse x.name);
/**
This function takes an argument `x` that's either a derivation or a
derivation's "name" attribute and extracts the version part from that
argument.
# Inputs
`x`
: 1\. Function argument
# Type
```
getVersion :: String | Derivation -> String
```
# Examples
:::{.example}
## `lib.strings.getVersion` usage example
```nix
getVersion "youtube-dl-2016.01.01"
=> "2016.01.01"
getVersion pkgs.youtube-dl
=> "2016.01.01"
```
:::
*/
getVersion = let
parse = drv: (parseDrvName drv).version;
in x:
if isString x
then parse x
else x.version or (parse x.name);
/**
Extract name and version from a URL as shown in the examples.
Separator `sep` is used to determine the end of the extension.
# Inputs
`url`
: 1\. Function argument
`sep`
: 2\. Function argument
# Type
```
nameFromURL :: String -> String
```
# Examples
:::{.example}
## `lib.strings.nameFromURL` usage example
```nix
nameFromURL "https://nixos.org/releases/nix/nix-1.7/nix-1.7-x86_64-linux.tar.bz2" "-"
=> "nix"
nameFromURL "https://nixos.org/releases/nix/nix-1.7/nix-1.7-x86_64-linux.tar.bz2" "_"
=> "nix-1.7-x86"
```
:::
*/
nameFromURL = url: sep:
let
components = splitString "/" url;
filename = lib.last components;
name = head (splitString sep filename);
in assert name != filename; name;
/**
Create a `"-D<feature>:<type>=<value>"` string that can be passed to typical
CMake invocations.
# Inputs
`feature`
: The feature to be set
`type`
: The type of the feature to be set, as described in
https://cmake.org/cmake/help/latest/command/set.html
the possible values (case insensitive) are:
BOOL FILEPATH PATH STRING INTERNAL
`value`
: The desired value
# Type
```
cmakeOptionType :: string -> string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.cmakeOptionType` usage example
```nix
cmakeOptionType "string" "ENGINE" "sdl2"
=> "-DENGINE:STRING=sdl2"
```
:::
*/
cmakeOptionType = let
types = [ "BOOL" "FILEPATH" "PATH" "STRING" "INTERNAL" ];
in type: feature: value:
assert (elem (toUpper type) types);
assert (isString feature);
assert (isString value);
"-D${feature}:${toUpper type}=${value}";
/**
Create a -D<condition>={TRUE,FALSE} string that can be passed to typical
CMake invocations.
# Inputs
`condition`
: The condition to be made true or false
`flag`
: The controlling flag of the condition
# Type
```
cmakeBool :: string -> bool -> string
```
# Examples
:::{.example}
## `lib.strings.cmakeBool` usage example
```nix
cmakeBool "ENABLE_STATIC_LIBS" false
=> "-DENABLESTATIC_LIBS:BOOL=FALSE"
```
:::
*/
cmakeBool = condition: flag:
assert (lib.isString condition);
assert (lib.isBool flag);
cmakeOptionType "bool" condition (lib.toUpper (lib.boolToString flag));
/**
Create a -D<feature>:STRING=<value> string that can be passed to typical
CMake invocations.
This is the most typical usage, so it deserves a special case.
# Inputs
`feature`
: The feature to be set
`value`
: The desired value
# Type
```
cmakeFeature :: string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.cmakeFeature` usage example
```nix
cmakeFeature "MODULES" "badblock"
=> "-DMODULES:STRING=badblock"
```
:::
*/
cmakeFeature = feature: value:
assert (lib.isString feature);
assert (lib.isString value);
cmakeOptionType "string" feature value;
/**
Create a -D<feature>=<value> string that can be passed to typical Meson
invocations.
# Inputs
`feature`
: The feature to be set
`value`
: The desired value
# Type
```
mesonOption :: string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.mesonOption` usage example
```nix
mesonOption "engine" "opengl"
=> "-Dengine=opengl"
```
:::
*/
mesonOption = feature: value:
assert (lib.isString feature);
assert (lib.isString value);
"-D${feature}=${value}";
/**
Create a -D<condition>={true,false} string that can be passed to typical
Meson invocations.
# Inputs
`condition`
: The condition to be made true or false
`flag`
: The controlling flag of the condition
# Type
```
mesonBool :: string -> bool -> string
```
# Examples
:::{.example}
## `lib.strings.mesonBool` usage example
```nix
mesonBool "hardened" true
=> "-Dhardened=true"
mesonBool "static" false
=> "-Dstatic=false"
```
:::
*/
mesonBool = condition: flag:
assert (lib.isString condition);
assert (lib.isBool flag);
mesonOption condition (lib.boolToString flag);
/**
Create a -D<feature>={enabled,disabled} string that can be passed to
typical Meson invocations.
# Inputs
`feature`
: The feature to be enabled or disabled
`flag`
: The controlling flag
# Type
```
mesonEnable :: string -> bool -> string
```
# Examples
:::{.example}
## `lib.strings.mesonEnable` usage example
```nix
mesonEnable "docs" true
=> "-Ddocs=enabled"
mesonEnable "savage" false
=> "-Dsavage=disabled"
```
:::
*/
mesonEnable = feature: flag:
assert (lib.isString feature);
assert (lib.isBool flag);
mesonOption feature (if flag then "enabled" else "disabled");
/**
Create an --{enable,disable}-<feature> string that can be passed to
standard GNU Autoconf scripts.
# Inputs
`flag`
: 1\. Function argument
`feature`
: 2\. Function argument
# Type
```
enableFeature :: bool -> string -> string
```
# Examples
:::{.example}
## `lib.strings.enableFeature` usage example
```nix
enableFeature true "shared"
=> "--enable-shared"
enableFeature false "shared"
=> "--disable-shared"
```
:::
*/
enableFeature = flag: feature:
assert lib.isBool flag;
assert lib.isString feature; # e.g. passing openssl instead of "openssl"
"--${if flag then "enable" else "disable"}-${feature}";
/**
Create an --{enable-<feature>=<value>,disable-<feature>} string that can be passed to
standard GNU Autoconf scripts.
# Inputs
`flag`
: 1\. Function argument
`feature`
: 2\. Function argument
`value`
: 3\. Function argument
# Type
```
enableFeatureAs :: bool -> string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.enableFeatureAs` usage example
```nix
enableFeatureAs true "shared" "foo"
=> "--enable-shared=foo"
enableFeatureAs false "shared" (throw "ignored")
=> "--disable-shared"
```
:::
*/
enableFeatureAs = flag: feature: value:
enableFeature flag feature + optionalString flag "=${value}";
/**
Create an --{with,without}-<feature> string that can be passed to
standard GNU Autoconf scripts.
# Inputs
`flag`
: 1\. Function argument
`feature`
: 2\. Function argument
# Type
```
withFeature :: bool -> string -> string
```
# Examples
:::{.example}
## `lib.strings.withFeature` usage example
```nix
withFeature true "shared"
=> "--with-shared"
withFeature false "shared"
=> "--without-shared"
```
:::
*/
withFeature = flag: feature:
assert isString feature; # e.g. passing openssl instead of "openssl"
"--${if flag then "with" else "without"}-${feature}";
/**
Create an --{with-<feature>=<value>,without-<feature>} string that can be passed to
standard GNU Autoconf scripts.
# Inputs
`flag`
: 1\. Function argument
`feature`
: 2\. Function argument
`value`
: 3\. Function argument
# Type
```
withFeatureAs :: bool -> string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.withFeatureAs` usage example
```nix
withFeatureAs true "shared" "foo"
=> "--with-shared=foo"
withFeatureAs false "shared" (throw "ignored")
=> "--without-shared"
```
:::
*/
withFeatureAs = flag: feature: value:
withFeature flag feature + optionalString flag "=${value}";
/**
Create a fixed width string with additional prefix to match
required width.
This function will fail if the input string is longer than the
requested length.
# Inputs
`width`
: 1\. Function argument
`filler`
: 2\. Function argument
`str`
: 3\. Function argument
# Type
```
fixedWidthString :: int -> string -> string -> string
```
# Examples
:::{.example}
## `lib.strings.fixedWidthString` usage example
```nix
fixedWidthString 5 "0" (toString 15)
=> "00015"
```
:::
*/
fixedWidthString = width: filler: str:
let
strw = lib.stringLength str;
reqWidth = width - (lib.stringLength filler);
in
assert lib.assertMsg (strw <= width)
"fixedWidthString: requested string length (${
toString width}) must not be shorter than actual length (${
toString strw})";
if strw == width then str else filler + fixedWidthString reqWidth filler str;
/**
Format a number adding leading zeroes up to fixed width.
# Inputs
`width`
: 1\. Function argument
`n`
: 2\. Function argument
# Type
```
fixedWidthNumber :: int -> int -> string
```
# Examples
:::{.example}
## `lib.strings.fixedWidthNumber` usage example
```nix
fixedWidthNumber 5 15
=> "00015"
```
:::
*/
fixedWidthNumber = width: n: fixedWidthString width "0" (toString n);
/**
Convert a float to a string, but emit a warning when precision is lost
during the conversion
# Inputs
`float`
: 1\. Function argument
# Type
```
floatToString :: float -> string
```
# Examples
:::{.example}
## `lib.strings.floatToString` usage example
```nix
floatToString 0.000001
=> "0.000001"
floatToString 0.0000001
=> trace: warning: Imprecise conversion from float to string 0.000000
"0.000000"
```
:::
*/
floatToString = float: let
result = toString float;
precise = float == fromJSON result;
in lib.warnIf (!precise) "Imprecise conversion from float to string ${result}"
result;
/**
Check whether a value `val` can be coerced to a string.
:::{.warning}
Soft-deprecated function. While the original implementation is available as
`isConvertibleWithToString`, consider using `isStringLike` instead, if suitable.
:::
# Inputs
`val`
: 1\. Function argument
# Type
```
isCoercibleToString :: a -> bool
```
*/
isCoercibleToString = lib.warnIf (lib.isInOldestRelease 2305)
"lib.strings.isCoercibleToString is deprecated in favor of either isStringLike or isConvertibleWithToString. Only use the latter if it needs to return true for null, numbers, booleans and list of similarly coercibles."
isConvertibleWithToString;
/**
Check whether a list or other value `x` can be passed to toString.
Many types of value are coercible to string this way, including `int`, `float`,
`null`, `bool`, `list` of similarly coercible values.
# Inputs
`val`
: 1\. Function argument
# Type
```
isConvertibleWithToString :: a -> bool
```
*/
isConvertibleWithToString = let
types = [ "null" "int" "float" "bool" ];
in x:
isStringLike x ||
elem (typeOf x) types ||
(isList x && lib.all isConvertibleWithToString x);
/**
Check whether a value can be coerced to a string.
The value must be a string, path, or attribute set.
String-like values can be used without explicit conversion in
string interpolations and in most functions that expect a string.
# Inputs
`x`
: 1\. Function argument
# Type
```
isStringLike :: a -> bool
```
*/
isStringLike = x:
isString x ||
isPath x ||
x ? outPath ||
x ? __toString;
/**
Check whether a value `x` is a store path.
# Inputs
`x`
: 1\. Function argument
# Type
```
isStorePath :: a -> bool
```
# Examples
:::{.example}
## `lib.strings.isStorePath` usage example
```nix
isStorePath "/nix/store/d945ibfx9x185xf04b890y4f9g3cbb63-python-2.7.11/bin/python"
=> false
isStorePath "/nix/store/d945ibfx9x185xf04b890y4f9g3cbb63-python-2.7.11"
=> true
isStorePath pkgs.python
=> true
isStorePath [] || isStorePath 42 || isStorePath {} || …
=> false
```
:::
*/
isStorePath = x:
if isStringLike x then
let str = toString x; in
substring 0 1 str == "/"
&& dirOf str == storeDir
else
false;
/**
Parse a string as an int. Does not support parsing of integers with preceding zero due to
ambiguity between zero-padded and octal numbers. See toIntBase10.
# Inputs
`str`
: A string to be interpreted as an int.
# Type
```
toInt :: string -> int
```
# Examples
:::{.example}
## `lib.strings.toInt` usage example
```nix
toInt "1337"
=> 1337
toInt "-4"
=> -4
toInt " 123 "
=> 123
toInt "00024"
=> error: Ambiguity in interpretation of 00024 between octal and zero padded integer.
toInt "3.14"
=> error: floating point JSON numbers are not supported
```
:::
*/
toInt =
let
matchStripInput = match "[[:space:]]*(-?[[:digit:]]+)[[:space:]]*";
matchLeadingZero = match "0[[:digit:]]+";
in
str:
let
# RegEx: Match any leading whitespace, possibly a '-', one or more digits,
# and finally match any trailing whitespace.
strippedInput = matchStripInput str;
# RegEx: Match a leading '0' then one or more digits.
isLeadingZero = matchLeadingZero (head strippedInput) == [];
# Attempt to parse input
parsedInput = fromJSON (head strippedInput);
generalError = "toInt: Could not convert ${escapeNixString str} to int.";
in
# Error on presence of non digit characters.
if strippedInput == null
then throw generalError
# Error on presence of leading zero/octal ambiguity.
else if isLeadingZero
then throw "toInt: Ambiguity in interpretation of ${escapeNixString str} between octal and zero padded integer."
# Error if parse function fails.
else if !isInt parsedInput
then throw generalError
# Return result.
else parsedInput;
/**
Parse a string as a base 10 int. This supports parsing of zero-padded integers.
# Inputs
`str`
: A string to be interpreted as an int.
# Type
```
toIntBase10 :: string -> int
```
# Examples
:::{.example}
## `lib.strings.toIntBase10` usage example
```nix
toIntBase10 "1337"
=> 1337
toIntBase10 "-4"
=> -4
toIntBase10 " 123 "
=> 123
toIntBase10 "00024"
=> 24
toIntBase10 "3.14"
=> error: floating point JSON numbers are not supported
```
:::
*/
toIntBase10 =
let
matchStripInput = match "[[:space:]]*0*(-?[[:digit:]]+)[[:space:]]*";
matchZero = match "0+";
in
str:
let
# RegEx: Match any leading whitespace, then match any zero padding,
# capture possibly a '-' followed by one or more digits,
# and finally match any trailing whitespace.
strippedInput = matchStripInput str;
# RegEx: Match at least one '0'.
isZero = matchZero (head strippedInput) == [];
# Attempt to parse input
parsedInput = fromJSON (head strippedInput);
generalError = "toIntBase10: Could not convert ${escapeNixString str} to int.";
in
# Error on presence of non digit characters.
if strippedInput == null
then throw generalError
# In the special case zero-padded zero (00000), return early.
else if isZero
then 0
# Error if parse function fails.
else if !isInt parsedInput
then throw generalError
# Return result.
else parsedInput;
/**
Read a list of paths from `file`, relative to the `rootPath`.
Lines beginning with `#` are treated as comments and ignored.
Whitespace is significant.
:::{.warning}
This function is deprecated and should be avoided.
:::
:::{.note}
This function is not performant and should be avoided.
:::
# Inputs
`rootPath`
: 1\. Function argument
`file`
: 2\. Function argument
# Type
```
readPathsFromFile :: string -> string -> [string]
```
# Examples
:::{.example}
## `lib.strings.readPathsFromFile` usage example
```nix
readPathsFromFile /prefix
./pkgs/development/libraries/qt-5/5.4/qtbase/series
=> [ "/prefix/dlopen-resolv.patch" "/prefix/tzdir.patch"
"/prefix/dlopen-libXcursor.patch" "/prefix/dlopen-openssl.patch"
"/prefix/dlopen-dbus.patch" "/prefix/xdg-config-dirs.patch"
"/prefix/nix-profiles-library-paths.patch"
"/prefix/compose-search-path.patch" ]
```
:::
*/
readPathsFromFile = lib.warn "lib.readPathsFromFile is deprecated, use a list instead."
(rootPath: file:
let
lines = lib.splitString "\n" (readFile file);
removeComments = lib.filter (line: line != "" && !(lib.hasPrefix "#" line));
relativePaths = removeComments lines;
absolutePaths = map (path: rootPath + "/${path}") relativePaths;
in
absolutePaths);
/**
Read the contents of a file removing the trailing \n
# Inputs
`file`
: 1\. Function argument
# Type
```
fileContents :: path -> string
```
# Examples
:::{.example}
## `lib.strings.fileContents` usage example
```nix
$ echo "1.0" > ./version
fileContents ./version
=> "1.0"
```
:::
*/
fileContents = file: removeSuffix "\n" (readFile file);
/**
Creates a valid derivation name from a potentially invalid one.
# Inputs
`string`
: 1\. Function argument
# Type
```
sanitizeDerivationName :: String -> String
```
# Examples
:::{.example}
## `lib.strings.sanitizeDerivationName` usage example
```nix
sanitizeDerivationName "../hello.bar # foo"
=> "-hello.bar-foo"
sanitizeDerivationName ""
=> "unknown"
sanitizeDerivationName pkgs.hello
=> "-nix-store-2g75chlbpxlrqn15zlby2dfh8hr9qwbk-hello-2.10"
```
:::
*/
sanitizeDerivationName =
let okRegex = match "[[:alnum:]+_?=-][[:alnum:]+._?=-]*";
in
string:
# First detect the common case of already valid strings, to speed those up
if stringLength string <= 207 && okRegex string != null
then unsafeDiscardStringContext string
else lib.pipe string [
# Get rid of string context. This is safe under the assumption that the
# resulting string is only used as a derivation name
unsafeDiscardStringContext
# Strip all leading "."
(x: elemAt (match "\\.*(.*)" x) 0)
# Split out all invalid characters
# https://github.com/NixOS/nix/blob/2.3.2/src/libstore/store-api.cc#L85-L112
# https://github.com/NixOS/nix/blob/2242be83c61788b9c0736a92bb0b5c7bbfc40803/nix-rust/src/store/path.rs#L100-L125
(split "[^[:alnum:]+._?=-]+")
# Replace invalid character ranges with a "-"
(concatMapStrings (s: if lib.isList s then "-" else s))
# Limit to 211 characters (minus 4 chars for ".drv")
(x: substring (lib.max (stringLength x - 207) 0) (-1) x)
# If the result is empty, replace it with "unknown"
(x: if stringLength x == 0 then "unknown" else x)
];
/**
Computes the Levenshtein distance between two strings `a` and `b`.
Complexity O(n*m) where n and m are the lengths of the strings.
Algorithm adjusted from https://stackoverflow.com/a/9750974/6605742
# Inputs
`a`
: 1\. Function argument
`b`
: 2\. Function argument
# Type
```
levenshtein :: string -> string -> int
```
# Examples
:::{.example}
## `lib.strings.levenshtein` usage example
```nix
levenshtein "foo" "foo"
=> 0
levenshtein "book" "hook"
=> 1
levenshtein "hello" "Heyo"
=> 3
```
:::
*/
levenshtein = a: b: let
# Two dimensional array with dimensions (stringLength a + 1, stringLength b + 1)
arr = lib.genList (i:
lib.genList (j:
dist i j
) (stringLength b + 1)
) (stringLength a + 1);
d = x: y: lib.elemAt (lib.elemAt arr x) y;
dist = i: j:
let c = if substring (i - 1) 1 a == substring (j - 1) 1 b
then 0 else 1;
in
if j == 0 then i
else if i == 0 then j
else lib.min
( lib.min (d (i - 1) j + 1) (d i (j - 1) + 1))
( d (i - 1) (j - 1) + c );
in d (stringLength a) (stringLength b);
/**
Returns the length of the prefix that appears in both strings `a` and `b`.
# Inputs
`a`
: 1\. Function argument
`b`
: 2\. Function argument
# Type
```
commonPrefixLength :: string -> string -> int
```
*/
commonPrefixLength = a: b:
let
m = lib.min (stringLength a) (stringLength b);
go = i: if i >= m then m else if substring i 1 a == substring i 1 b then go (i + 1) else i;
in go 0;
/**
Returns the length of the suffix common to both strings `a` and `b`.
# Inputs
`a`
: 1\. Function argument
`b`
: 2\. Function argument
# Type
```
commonSuffixLength :: string -> string -> int
```
*/
commonSuffixLength = a: b:
let
m = lib.min (stringLength a) (stringLength b);
go = i: if i >= m then m else if substring (stringLength a - i - 1) 1 a == substring (stringLength b - i - 1) 1 b then go (i + 1) else i;
in go 0;
/**
Returns whether the levenshtein distance between two strings `a` and `b` is at most some value `k`.
Complexity is O(min(n,m)) for k <= 2 and O(n*m) otherwise
# Inputs
`k`
: Distance threshold
`a`
: String `a`
`b`
: String `b`
# Type
```
levenshteinAtMost :: int -> string -> string -> bool
```
# Examples
:::{.example}
## `lib.strings.levenshteinAtMost` usage example
```nix
levenshteinAtMost 0 "foo" "foo"
=> true
levenshteinAtMost 1 "foo" "boa"
=> false
levenshteinAtMost 2 "foo" "boa"
=> true
levenshteinAtMost 2 "This is a sentence" "this is a sentense."
=> false
levenshteinAtMost 3 "This is a sentence" "this is a sentense."
=> true
```
:::
*/
levenshteinAtMost = let
infixDifferAtMost1 = x: y: stringLength x <= 1 && stringLength y <= 1;
# This function takes two strings stripped by their common pre and suffix,
# and returns whether they differ by at most two by Levenshtein distance.
# Because of this stripping, if they do indeed differ by at most two edits,
# we know that those edits were (if at all) done at the start or the end,
# while the middle has to have stayed the same. This fact is used in the
# implementation.
infixDifferAtMost2 = x: y:
let
xlen = stringLength x;
ylen = stringLength y;
# This function is only called with |x| >= |y| and |x| - |y| <= 2, so
# diff is one of 0, 1 or 2
diff = xlen - ylen;
# Infix of x and y, stripped by the left and right most character
xinfix = substring 1 (xlen - 2) x;
yinfix = substring 1 (ylen - 2) y;
# x and y but a character deleted at the left or right
xdelr = substring 0 (xlen - 1) x;
xdell = substring 1 (xlen - 1) x;
ydelr = substring 0 (ylen - 1) y;
ydell = substring 1 (ylen - 1) y;
in
# A length difference of 2 can only be gotten with 2 delete edits,
# which have to have happened at the start and end of x
# Example: "abcdef" -> "bcde"
if diff == 2 then xinfix == y
# A length difference of 1 can only be gotten with a deletion on the
# right and a replacement on the left or vice versa.
# Example: "abcdef" -> "bcdez" or "zbcde"
else if diff == 1 then xinfix == ydelr || xinfix == ydell
# No length difference can either happen through replacements on both
# sides, or a deletion on the left and an insertion on the right or
# vice versa
# Example: "abcdef" -> "zbcdez" or "bcdefz" or "zabcde"
else xinfix == yinfix || xdelr == ydell || xdell == ydelr;
in k: if k <= 0 then a: b: a == b else
let f = a: b:
let
alen = stringLength a;
blen = stringLength b;
prelen = commonPrefixLength a b;
suflen = commonSuffixLength a b;
presuflen = prelen + suflen;
ainfix = substring prelen (alen - presuflen) a;
binfix = substring prelen (blen - presuflen) b;
in
# Make a be the bigger string
if alen < blen then f b a
# If a has over k more characters than b, even with k deletes on a, b can't be reached
else if alen - blen > k then false
else if k == 1 then infixDifferAtMost1 ainfix binfix
else if k == 2 then infixDifferAtMost2 ainfix binfix
else levenshtein ainfix binfix <= k;
in f;
}
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