array(3erl) Erlang Module Definition array(3erl)
NAME
array - Functional, extendible arrays.
DESCRIPTION
Functional, extendible arrays. Arrays can have fixed size, or can grow
automatically as needed. A default value is used for entries that have
not been explicitly set.
Arrays uses zero-based indexing. This is a deliberate design choice and
differs from other Erlang data structures, for example, tuples.
Unless specified by the user when the array is created, the default
value is the atom undefined. There is no difference between an unset
entry and an entry that has been explicitly set to the same value as
the default one (compare reset/2). If you need to differentiate between
unset and set entries, ensure that the default value cannot be confused
with the values of set entries.
The array never shrinks automatically. If an index I has been used to
set an entry successfully, all indices in the range [0,I] stay accessi-
ble unless the array size is explicitly changed by calling resize/2.
Examples:
Create a fixed-size array with entries 0-9 set to undefined:
A0 = array:new(10).
10 = array:size(A0).
Create an extendible array and set entry 17 to true, causing the array
to grow automatically:
A1 = array:set(17, true, array:new()).
18 = array:size(A1).
Read back a stored value:
true = array:get(17, A1).
Accessing an unset entry returns default value:
undefined = array:get(3, A1)
Accessing an entry beyond the last set entry also returns the default
value, if the array does not have fixed size:
undefined = array:get(18, A1).
"Sparse" functions ignore default-valued entries:
A2 = array:set(4, false, A1).
[{4, false}, {17, true}] = array:sparse_to_orddict(A2).
An extendible array can be made fixed-size later:
A3 = array:fix(A2).
A fixed-size array does not grow automatically and does not allow ac-
cesses beyond the last set entry:
{'EXIT',{badarg,_}} = (catch array:set(18, true, A3)).
{'EXIT',{badarg,_}} = (catch array:get(18, A3)).
DATA TYPES
array(Type)
A functional, extendible array. The representation is not docu-
mented and is subject to change without notice. Notice that ar-
rays cannot be directly compared for equality.
array() = array(term())
array_indx() = integer() >= 0
array_opts() = array_opt() | [array_opt()]
array_opt() =
{fixed, boolean()} |
fixed |
{default, Type :: term()} |
{size, N :: integer() >= 0} |
(N :: integer() >= 0)
indx_pairs(Type) = [indx_pair(Type)]
indx_pair(Type) = {Index :: array_indx(), Type}
EXPORTS
default(Array :: array(Type)) -> Value :: Type
Gets the value used for uninitialized entries.
See also new/2.
fix(Array :: array(Type)) -> array(Type)
Fixes the array size. This prevents it from growing automati-
cally upon insertion.
See also set/3 and relax/1.
foldl(Function, InitialAcc :: A, Array :: array(Type)) -> B
Types:
Function =
fun((Index :: array_indx(), Value :: Type, Acc :: A) ->
B)
Folds the array elements using the specified function and ini-
tial accumulator value. The elements are visited in order from
the lowest index to the highest. If Function is not a function,
the call fails with reason badarg.
See also foldr/3, map/2, sparse_foldl/3.
foldr(Function, InitialAcc :: A, Array :: array(Type)) -> B
Types:
Function =
fun((Index :: array_indx(), Value :: Type, Acc :: A) ->
B)
Folds the array elements right-to-left using the specified func-
tion and initial accumulator value. The elements are visited in
order from the highest index to the lowest. If Function is not a
function, the call fails with reason badarg.
See also foldl/3, map/2.
from_list(List :: [Value :: Type]) -> array(Type)
Equivalent to from_list(List, undefined).
from_list(List :: [Value :: Type], Default :: term()) ->
array(Type)
Converts a list to an extendible array. Default is used as the
value for uninitialized entries of the array. If List is not a
proper list, the call fails with reason badarg.
See also new/2, to_list/1.
from_orddict(Orddict :: indx_pairs(Value :: Type)) -> array(Type)
Equivalent to from_orddict(Orddict, undefined).
from_orddict(Orddict :: indx_pairs(Value :: Type),
Default :: Type) ->
array(Type)
Converts an ordered list of pairs {Index, Value} to a corre-
sponding extendible array. Default is used as the value for
uninitialized entries of the array. If Orddict is not a proper,
ordered list of pairs whose first elements are non-negative in-
tegers, the call fails with reason badarg.
See also new/2, to_orddict/1.
get(I :: array_indx(), Array :: array(Type)) -> Value :: Type
Gets the value of entry I. If I is not a non-negative integer,
or if the array has fixed size and I is larger than the maximum
index, the call fails with reason badarg.
If the array does not have fixed size, the default value for any
index I greater than size(Array)-1 is returned.
See also set/3.
is_array(X :: term()) -> boolean()
Returns true if X is an array, otherwise false. Notice that the
check is only shallow, as there is no guarantee that X is a
well-formed array representation even if this function returns
true.
is_fix(Array :: array()) -> boolean()
Checks if the array has fixed size. Returns true if the array is
fixed, otherwise false.
See also fix/1.
map(Function, Array :: array(Type1)) -> array(Type2)
Types:
Function = fun((Index :: array_indx(), Type1) -> Type2)
Maps the specified function onto each array element. The ele-
ments are visited in order from the lowest index to the highest.
If Function is not a function, the call fails with reason
badarg.
See also foldl/3, foldr/3, sparse_map/2.
new() -> array()
Creates a new, extendible array with initial size zero.
See also new/1, new/2.
new(Options :: array_opts()) -> array()
Creates a new array according to the specified otions. By de-
fault, the array is extendible and has initial size zero. Array
indices start at 0.
Options is a single term or a list of terms, selected from the
following:
N::integer() >= 0 or {size, N::integer() >= 0}:
Specifies the initial array size; this also implies {fixed,
true}. If N is not a non-negative integer, the call fails
with reason badarg.
fixed or {fixed, true}:
Creates a fixed-size array. See also fix/1.
{fixed, false}:
Creates an extendible (non-fixed-size) array.
{default, Value}:
Sets the default value for the array to Value.
Options are processed in the order they occur in the list, that
is, later options have higher precedence.
The default value is used as the value of uninitialized entries,
and cannot be changed once the array has been created.
Examples:
array:new(100)
creates a fixed-size array of size 100.
array:new({default,0})
creates an empty, extendible array whose default value is 0.
array:new([{size,10},{fixed,false},{default,-1}])
creates an extendible array with initial size 10 whose default
value is -1.
See also fix/1, from_list/2, get/2, new/0, new/2, set/3.
new(Size :: integer() >= 0, Options :: array_opts()) -> array()
Creates a new array according to the specified size and options.
If Size is not a non-negative integer, the call fails with rea-
son badarg. By default, the array has fixed size. Notice that
any size specifications in Options override parameter Size.
If Options is a list, this is equivalent to new([{size, Size} |
Options], otherwise it is equivalent to new([{size, Size} | [Op-
tions]]. However, using this function directly is more effi-
cient.
Example:
array:new(100, {default,0})
creates a fixed-size array of size 100, whose default value is
0.
See also new/1.
relax(Array :: array(Type)) -> array(Type)
Makes the array resizable. (Reverses the effects of fix/1.)
See also fix/1.
reset(I :: array_indx(), Array :: array(Type)) -> array(Type)
Resets entry I to the default value for the array. If the value
of entry I is the default value, the array is returned un-
changed. Reset never changes the array size. Shrinking can be
done explicitly by calling resize/2.
If I is not a non-negative integer, or if the array has fixed
size and I is larger than the maximum index, the call fails with
reason badarg; compare set/3
See also new/2, set/3.
resize(Array :: array(Type)) -> array(Type)
Changes the array size to that reported by sparse_size/1. If the
specified array has fixed size, also the resulting array has
fixed size.
See also resize/2, sparse_size/1.
resize(Size :: integer() >= 0, Array :: array(Type)) ->
array(Type)
Change the array size. If Size is not a non-negative integer,
the call fails with reason badarg. If the specified array has
fixed size, also the resulting array has fixed size.
set(I :: array_indx(), Value :: Type, Array :: array(Type)) ->
array(Type)
Sets entry I of the array to Value. If I is not a non-negative
integer, or if the array has fixed size and I is larger than the
maximum index, the call fails with reason badarg.
If the array does not have fixed size, and I is greater than
size(Array)-1, the array grows to size I+1.
See also get/2, reset/2.
size(Array :: array()) -> integer() >= 0
Gets the number of entries in the array. Entries are numbered
from 0 to size(Array)-1. Hence, this is also the index of the
first entry that is guaranteed to not have been previously set.
See also set/3, sparse_size/1.
sparse_foldl(Function, InitialAcc :: A, Array :: array(Type)) -> B
Types:
Function =
fun((Index :: array_indx(), Value :: Type, Acc :: A) ->
B)
Folds the array elements using the specified function and ini-
tial accumulator value, skipping default-valued entries. The el-
ements are visited in order from the lowest index to the high-
est. If Function is not a function, the call fails with reason
badarg.
See also foldl/3, sparse_foldr/3.
sparse_foldr(Function, InitialAcc :: A, Array :: array(Type)) -> B
Types:
Function =
fun((Index :: array_indx(), Value :: Type, Acc :: A) ->
B)
Folds the array elements right-to-left using the specified func-
tion and initial accumulator value, skipping default-valued en-
tries. The elements are visited in order from the highest index
to the lowest. If Function is not a function, the call fails
with reason badarg.
See also foldr/3, sparse_foldl/3.
sparse_map(Function, Array :: array(Type1)) -> array(Type2)
Types:
Function = fun((Index :: array_indx(), Type1) -> Type2)
Maps the specified function onto each array element, skipping
default-valued entries. The elements are visited in order from
the lowest index to the highest. If Function is not a function,
the call fails with reason badarg.
See also map/2.
sparse_size(Array :: array()) -> integer() >= 0
Gets the number of entries in the array up until the last non-
default-valued entry. That is, returns I+1 if I is the last non-
default-valued entry in the array, or zero if no such entry ex-
ists.
See also resize/1, size/1.
sparse_to_list(Array :: array(Type)) -> [Value :: Type]
Converts the array to a list, skipping default-valued entries.
See also to_list/1.
sparse_to_orddict(Array :: array(Type)) ->
indx_pairs(Value :: Type)
Converts the array to an ordered list of pairs {Index, Value},
skipping default-valued entries.
See also to_orddict/1.
to_list(Array :: array(Type)) -> [Value :: Type]
Converts the array to a list.
See also from_list/2, sparse_to_list/1.
to_orddict(Array :: array(Type)) -> indx_pairs(Value :: Type)
Converts the array to an ordered list of pairs {Index, Value}.
See also from_orddict/2, sparse_to_orddict/1.
Ericsson AB stdlib 3.13 array(3erl)