# Class: Sass::Util::SubsetMap

- Inherits:
- Object
- Object
- Sass::Util::SubsetMap

- Defined in:
- /home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb

## Overview

A map from sets to values. A value is set by providing a set (the "set-set") and a value, which is then recorded as corresponding to that set. Values are accessed by providing a set (the "get-set") and returning all values that correspond to set-sets that are subsets of the get-set.

SubsetMap preserves the order of values as they're inserted.

## Instance Method Summary (collapse)

- - (Array)
**[]**(set)Same as #get, but doesn't return the subsets of the argument for which values were found.

- -
**[]=**(set, value)Associates a value with a set.

- -
**each_value**{|Object| ... }Iterates over each value in the subset map.

- - (Boolean)
**empty?**Whether or not this SubsetMap has any key-value pairs.

- - (Array<(Object, #to_set)>)
**get**(set)Returns all values associated with subsets of

`set`

. - - (SubsetMap)
**initialize**constructorCreates a new, empty SubsetMap.

## Constructor Details

### - (`SubsetMap`) **initialize**

Creates a new, empty SubsetMap.

23 24 25 26 | ```
# File '/home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb', line 23
def initialize
@hash = {}
@vals = []
end
``` |

## Instance Method Details

### - (`Array`) **[]**(set)

Same as #get, but doesn't return the subsets of the argument for which values were found.

96 97 98 | ```
# File '/home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb', line 96
def [](set)
get(set).map {|v, _| v}
end
``` |

### - **[]=**(set, value)

Associates a value with a set. When `set`

or any of its supersets is accessed, `value`

will be among the values returned.

Note that if the same `set`

is passed to this method multiple times, all given `value`

s will be associated with that `set`

.

This runs in `O(n)`

time, where `n`

is the size of `set`

.

47 48 49 50 51 52 53 54 55 56 | ```
# File '/home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb', line 47
def []=(set, value)
raise ArgumentError.new("SubsetMap keys may not be empty.") if set.empty?
index = @vals.size
@vals << value
set.each do |k|
@hash[k] ||= []
@hash[k] << [set, set.to_set, index]
end
end
``` |

### - **each_value** {|Object| ... }

Iterates over each value in the subset map. Ignores keys completely. If multiple keys have the same value, this will return them multiple times.

104 105 106 | ```
# File '/home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb', line 104
def each_value
@vals.each {|v| yield v}
end
``` |

### - (`Boolean`) **empty?**

Whether or not this SubsetMap has any key-value pairs.

31 32 33 | ```
# File '/home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb', line 31
def empty?
@hash.empty?
end
``` |

### - (`Array<(Object, #to_set)>`) **get**(set)

Returns all values associated with subsets of `set`

.

In the worst case, this runs in `O(m*max(n, log m))`

time, where `n`

is the size of `set`

and `m`

is the number of associations in the map. However, unless many keys in the map overlap with `set`

, `m`

will typically be much smaller.

73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 | ```
# File '/home/nweiz/code/sass-site/.sass/lib/sass/util/subset_map.rb', line 73
def get(set)
res = set.map do |k|
subsets = @hash[k]
next unless subsets
subsets.map do |subenum, subset, index|
next unless subset.subset?(set)
[index, subenum]
end
end.flatten(1)
res.compact!
res.uniq!
res.sort!
res.map! {|i, s| [@vals[i], s]}
res
end
``` |