new ()-#{}
Returns a new, empty mapping group.
1> maps:new ().
#{}
to_list (M), [{K1,v1}, ..., {KN,VN}]
Converts all keys and values in the mapping group M to a list of key values. The keys are sorted in ascending order in the generated list.
1> M = #{age = +, name + DMM}.
#{age = 18,name = DMM}
2> maps:to_list (M).
[{AGE,18},{NAME,DMM}]
From_list ([{k1,v1},..., {KN,VN}]), M
Converts a list of key-value pairs into a mapping group M. If the same key appears more than once, the last value associated with the list is used, and the preceding values are ignored.
1> T = [{age,18},{name,dmm},{age,19}].
[{age,18},{name,dmm},{age,19}]
2> maps:from_list (T).
#{age = 19,name = DMM}
size (Map), Integer () >= 0
Returns the number of entries in the Mapping group.
1> Map = #{42 = value_two,1337 = "Value One", "a" and "= 1}".
#{42 = value_two,1337 = "Value One", "a" and "= 1}"
2> maps:size (MAP).
3
Is_key (Key, MAP), BOOL ()
Returns true if the mapping group contains an entry with key keys, otherwise false is returned.
1> Map = #{"All" and "= value".
#{"+" = value}
2> Maps:is_key ("a", Map).
True
3> Maps:is_key (Value,map).
False
get (Key, Map), Val
Returns the value associated with the Key in the mapping group, or throws an exception error.
1> Map = #{42 = value_two,1337 = "Value One", "a" and "= 1}".
#{42 = value_two,1337 = "Value One", "a" and "= 1}"
2> Maps:get ("a", Map).
1
3> Maps:get (2,map).
* * Exception error: {badkey,2}
in function MAPS:GET/2
Called as maps:get (2,#{42 = value_two,1337 = "Value One", "a" and "= 1}")
get (Key, Map, Default), Value | Default
Returns the value associated with the key in the mapping group, and throws a default value if no key is available.
1> Map = #{Key1 = val1, Key2 = Val2}.
#{key1 = Val1,key2 = Val2}
2> Maps:get (Key1, Map, "Default value").
Val1
3> Maps:get (Key3, Map, "Default value").
"Default value"
Find (Key, Map), {OK, Value} | Error
Returns the value associated with the Key in the mapping group, otherwise returns an error.
1> Map = #{"Hi" = 42}.
#{"HI" = 42}
2> maps:find ("Hi", Map).
{ok,42}
3> maps:find ("HI", Map).
Error
keys (MAP), [Key1,.. KeyN]
Returns a list of the keys contained in the mapping group, sorted in ascending order.
1> Map = #{42 = value_three,1337 = "Value", "a" and "= 1}".
#{42 = value_three,1337 = "Value", "a" and "= 1}"
2> Maps:keys (MAP).
[42,1337, "a"]
Remove (Key, M), M1
Returns a new mapping group M1 except for keys that are key, except that the others are identical to M.
1> Map = #{"a" = 1}.
#{"A" = 1}
2> Maps:remove ("a", Map).
#{}
3> Maps:remove ("B", Map).
#{"A" = 1}
with ([Key1,.., KeyN], Map1), Map2
Returns a new mapping group MAP2, which is an assignment of MAP1, but has only the elements of these keys in the [Key1, ..., KeyN] list.
1> Map = #{42 = value_three,1337 = "Value", "a" and "= 1}".
#{42 = value_three,1337 = "Value", "a" and "= 1}"
2> Maps:with (["A", "a", "a", "other"],map).
#{42 = Value_three, "a" = 1}
without ([Key1,..., keyn],m), M1
Returns a new mapping group M1, which is a copy of M, except for the elements of these keys in the list with [Key1, ..., KeyN].
1> Map = #{42 = value_three,1337 = "Value", "a" and "= 1}".
#{42 = value_three,1337 = "Value", "a" and "= 1}"
2> Maps:without (["A", "a", "a", "other"],map).
#{1337 = "Value"}
Erlang Standard library Maps