nixpkgs/lib/strings.nix
Eelco Dolstra 2d9885db9e Remove eqStrings
It's no longer needed. Also clean up some comments.
2015-07-24 15:58:34 +02:00

223 lines
6.8 KiB
Nix
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

/* String manipulation functions. */
let lib = import ./default.nix;
inherit (builtins) length;
in
rec {
inherit (builtins) stringLength substring head tail isString replaceStrings;
# Concatenate a list of strings.
concatStrings =
if builtins ? concatStringsSep then
builtins.concatStringsSep ""
else
lib.foldl' (x: y: x + y) "";
# Map a function over a list and concatenate the resulting strings.
concatMapStrings = f: list: concatStrings (map f list);
concatImapStrings = f: list: concatStrings (lib.imap f list);
# Place an element between each element of a list, e.g.,
# `intersperse "," ["a" "b" "c"]' returns ["a" "," "b" "," "c"].
intersperse = separator: list:
if list == [] || length list == 1
then list
else [(head list) separator]
++ (intersperse separator (tail list));
# Concatenate a list of strings with a separator between each element, e.g.
# concatStringsSep " " ["foo" "bar" "xyzzy"] == "foo bar xyzzy"
concatStringsSep = builtins.concatStringsSep or (separator: list:
concatStrings (intersperse separator list));
concatMapStringsSep = sep: f: list: concatStringsSep sep (map f list);
concatImapStringsSep = sep: f: list: concatStringsSep sep (lib.imap f list);
# Construct a Unix-style search path consisting of each `subDir"
# directory of the given list of packages. For example,
# `makeSearchPath "bin" ["x" "y" "z"]' returns "x/bin:y/bin:z/bin".
makeSearchPath = subDir: packages:
concatStringsSep ":" (map (path: path + "/" + subDir) packages);
# Construct a library search path (such as RPATH) containing the
# libraries for a set of packages, e.g. "${pkg1}/lib:${pkg2}/lib:...".
makeLibraryPath = makeSearchPath "lib";
# Idem for Perl search paths.
makePerlPath = makeSearchPath "lib/perl5/site_perl";
# Dependening on the boolean `cond', return either the given string
# or the empty string.
optionalString = cond: string: if cond then string else "";
# Determine whether a string has given prefix/suffix.
hasPrefix = pref: str:
substring 0 (stringLength pref) str == pref;
hasSuffix = suff: str:
let
lenStr = stringLength str;
lenSuff = stringLength suff;
in lenStr >= lenSuff &&
substring (lenStr - lenSuff) lenStr str == suff;
# Convert a string to a list of characters (i.e. singleton strings).
# For instance, "abc" becomes ["a" "b" "c"]. 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.
stringToCharacters = s:
map (p: substring p 1 s) (lib.range 0 (stringLength s - 1));
# Manipulate a string charactter by character and replace them by
# strings before concatenating the results.
stringAsChars = f: s:
concatStrings (
map f (stringToCharacters s)
);
# Escape occurrence of the elements of list in string by
# prefixing it with a backslash. For example, escape ["(" ")"]
# "(foo)" returns the string \(foo\).
escape = list: replaceChars list (map (c: "\\${c}") list);
# Escape all characters that have special meaning in the Bourne shell.
escapeShellArg = lib.escape (stringToCharacters "\\ ';$`()|<>\t*[]");
# Obsolete - use replaceStrings instead.
replaceChars = builtins.replaceStrings or (
del: new: s:
let
substList = lib.zipLists del new;
subst = c:
let found = lib.findFirst (sub: sub.fst == c) null substList; in
if found == null then
c
else
found.snd;
in
stringAsChars subst s);
# Case conversion utilities.
lowerChars = stringToCharacters "abcdefghijklmnopqrstuvwxyz";
upperChars = stringToCharacters "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
toLower = replaceChars upperChars lowerChars;
toUpper = replaceChars lowerChars upperChars;
# Appends string context from another string.
addContextFrom = a: b: substring 0 0 a + b;
# Cut a string with a separator and produces a list of strings which were
# separated by this separator. e.g.,
# `splitString "." "foo.bar.baz"' returns ["foo" "bar" "baz"].
splitString = _sep: _s:
let
sep = addContextFrom _s _sep;
s = addContextFrom _sep _s;
sepLen = stringLength sep;
sLen = stringLength s;
lastSearch = sLen - sepLen;
startWithSep = startAt:
substring startAt sepLen s == sep;
recurse = index: startAt:
let cutUntil = i: [(substring startAt (i - startAt) s)]; in
if index < lastSearch then
if startWithSep index then
let restartAt = index + sepLen; in
cutUntil index ++ recurse restartAt restartAt
else
recurse (index + 1) startAt
else
cutUntil sLen;
in
recurse 0 0;
# return the suffix of the second argument if the first argument match its
# prefix. e.g.,
# `removePrefix "foo." "foo.bar.baz"' returns "bar.baz".
removePrefix = pre: s:
let
preLen = stringLength pre;
sLen = stringLength s;
in
if hasPrefix pre s then
substring preLen (sLen - preLen) s
else
s;
removeSuffix = suf: s:
let
sufLen = stringLength suf;
sLen = stringLength s;
in
if sufLen <= sLen && suf == substring (sLen - sufLen) sufLen s then
substring 0 (sLen - sufLen) s
else
s;
# Return true iff string v1 denotes a version older than v2.
versionOlder = v1: v2: builtins.compareVersions v2 v1 == 1;
# Return true iff string v1 denotes a version equal to or newer than v2.
versionAtLeast = v1: v2: !versionOlder v1 v2;
# Get the version of the specified derivation, as specified in its
# name attribute.
getVersion = drv: (builtins.parseDrvName drv.name).version;
# Extract name with version from URL. Ask for separator which is
# supposed to start extension.
nameFromURL = url: sep:
let
components = splitString "/" url;
filename = lib.last components;
name = builtins.head (splitString sep filename);
in assert name != filename; name;
# Create an --{enable,disable}-<feat> string that can be passed to
# standard GNU Autoconf scripts.
enableFeature = enable: feat: "--${if enable then "enable" else "disable"}-${feat}";
# Create a fixed width string with additional prefix to match
# required width.
fixedWidthString = width: filler: str:
let
strw = lib.stringLength str;
reqWidth = width - (lib.stringLength filler);
in
assert strw <= width;
if strw == width then str else filler + fixedWidthString reqWidth filler str;
# Format a number adding leading zeroes up to fixed width.
fixedWidthNumber = width: n: fixedWidthString width "0" (toString n);
}