* New functions: id, any, all, same as in Haskell.

* Function `sourceFilesBySuffices' to import all files matching given
  extensions in a directory.

svn path=/nixpkgs/trunk/; revision=10072
This commit is contained in:
Eelco Dolstra 2008-01-04 15:06:16 +00:00
parent 7a3501953c
commit 8c615616c7

View file

@ -9,6 +9,12 @@ in
rec {
# Identity function.
id = x: x;
# !!! need documentation...
innerSumArgs = f : x : y : (if y == null then (f x)
else (innerSumArgs f (x // y)));
sumArgs = f : innerSumArgs f {};
@ -19,6 +25,7 @@ rec {
f (tail (tail l));
pairMap = innerPairMap [];
# "Fold" a binary function `op' between successive elements of
# `list' with `nul' as the starting value, i.e., `fold op nul [x_1
# x_2 ... x_n] == op x_1 (op x_2 ... (op x_n nul))'. (This is
@ -65,14 +72,12 @@ rec {
# "y"] applied to some set e returns e.x.y, if it exists. The
# default value is returned otherwise.
getAttr = attrPath: default: e:
let {
attr = head attrPath;
body =
if attrPath == [] then e
else if builtins ? hasAttr && builtins.hasAttr attr e
then getAttr (tail attrPath) default (builtins.getAttr attr e)
else default;
};
let attr = head attrPath;
in
if attrPath == [] then e
else if builtins ? hasAttr && builtins.hasAttr attr e
then getAttr (tail attrPath) default (builtins.getAttr attr e)
else default;
# Filter a list using a predicate; that is, return a list containing
@ -95,15 +100,33 @@ rec {
else head found;
# Return true iff function `pred' returns true for at least element
# of `list'.
any = pred: list:
if list == [] then false
else if pred (head list) then true
else any pred (tail list);
# Return true iff function `pred' returns true for all elements of
# `list'.
all = pred: list:
if list == [] then true
else if pred (head list) then all pred (tail list)
else false;
# Return true if each element of a list is equal, false otherwise.
eqLists = xs: ys:
if xs == [] && ys == [] then true
else if xs == [] || ys == [] then false
else head xs == head ys && eqLists (tail xs) (tail ys);
# Workaround, but works in stable Nix now.
eqStrings = a: b: (a+(substring 0 0 b)) == ((substring 0 0 a)+b);
# Determine whether a filename ends in the given suffix.
hasSuffix = ext: fileName:
let lenFileName = stringLength fileName;
@ -125,6 +148,15 @@ rec {
in src: builtins.filterSource filter src;
# Get all files ending with the specified suffices from the given
# directory. E.g. `sourceFilesBySuffices ./dir [".xml" ".c"]'.
sourceFilesBySuffices = path: exts:
let filter = name: type:
let base = baseNameOf (toString name);
in type != "directory" && any (ext: hasSuffix ext base) exts;
in builtins.filterSource filter path;
# Return a singleton list or an empty list, depending on a boolean
# value. Useful when building lists with optional elements
# (e.g. `++ optional (system == "i686-linux") flashplayer').