87 lines
3.1 KiB
Nix
87 lines
3.1 KiB
Nix
/* String manipulation functions. */
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let lib = import ./default.nix; in
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rec {
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inherit (builtins) stringLength substring head tail lessThan sub;
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# Concatenate a list of strings.
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concatStrings = lib.fold (x: y: x + y) "";
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# Map a function over a list and concatenate the resulting strings.
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concatMapStrings = f: list: concatStrings (map f list);
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# Place an element between each element of a list, e.g.,
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# `intersperse "," ["a" "b" "c"]' returns ["a" "," "b" "," "c"].
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intersperse = separator: list:
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if list == [] || tail list == []
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then list
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else [(head list) separator]
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++ (intersperse separator (tail list));
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# Concatenate a list of strings with a separator between each element, e.g.
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# concatStringsSep " " ["foo" "bar" "xyzzy"] == "foo bar xyzzy"
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concatStringsSep = separator: list:
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concatStrings (intersperse separator list);
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# Construct an RPATH containing the libraries for a set of packages,
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# e.g. "${pkg1}/lib:${pkg2}/lib:...".
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makeLibraryPath = paths: concatStringsSep ":" (map (path: path + "/lib") paths);
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# Dependening on the boolean `cond', return either the given string
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# or the empty string.
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optionalString = cond: string: if cond then string else "";
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# Determine whether a filename ends in the given suffix.
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hasSuffix = ext: fileName:
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let lenFileName = stringLength fileName;
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lenExt = stringLength ext;
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in !(lessThan lenFileName lenExt) &&
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substring (sub lenFileName lenExt) lenFileName fileName == ext;
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# Convert a string to a list of characters (i.e. singleton strings).
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# For instance, "abc" becomes ["a" "b" "c"]. This allows you to,
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# e.g., map a function over each character. However, note that this
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# will likely be horribly inefficient; Nix is not a general purpose
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# programming language. Complex string manipulations should, if
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# appropriate, be done in a derivation.
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stringToCharacters = s: let l = stringLength s; in
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if l == 0
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then []
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else [(substring 0 1 s)] ++ stringToCharacters (substring 1 (builtins.sub l 1) s);
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# !!! this function seems broken - it doesn't escape all special
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# characters, and in any case this should be done in a builder.
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escapeShellArg = s:
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let escapeChar = x: if x == "'" then "'\"'\"'" else x;
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in "'" + concatStrings (map escapeChar (stringToCharacters s)) + "'";
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# !!! what is this for?
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defineShList = name: list: "\n${name}=(${concatStringsSep " " (map escapeShellArg list)})\n";
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# arg: http://foo/bar/bz.ext returns bz.ext
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# !!! isn't this what the `baseNameOf' primop does?
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dropPath = s :
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if s == "" then "" else
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let takeTillSlash = left : c : s :
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if left == 0 then s
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else if (__substring left 1 s == "/") then
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(__substring (__add left 1) (__sub c 1) s)
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else takeTillSlash (__sub left 1) (__add c 1) s; in
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takeTillSlash (__sub (__stringLength s) 1) 1 s;
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# Compares strings not requiring context equality
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# Obviously, a workaround but works on all Nix versions
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eqStrings = a: b: (a+(substring 0 0 b)) == ((substring 0 0 a)+b);
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}
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