selectPairs -- select a part of a hash table by pairs

Synopsis

• Usage:

  selectPairs(x, f)

  selectPairs(n, x, f)

• Inputs:
  • n, an integer,
  • x, a hash table, must be immutable;
  • f, a function,
• Outputs:
  • a hash table, containing all (or n, if it is given) key-value pairs (k,v) from x for which f(k,v) evaluates to true.

Description

i1 : x = hashTable{(1, 2), (2, 4), (3, 6), (4, 8), (5, 10)}

o1 = HashTable{1 => 2 }
               2 => 4
               3 => 6
               4 => 8
               5 => 10

o1 : HashTable

i2 : selectPairs(x, (k,v) -> odd(k + v))

o2 = HashTable{1 => 2 }
               3 => 6
               5 => 10

o2 : HashTable

i3 : selectPairs(2, x, (k, v) -> odd(k + v))

o3 = HashTable{1 => 2}
               3 => 6

o3 : HashTable

See also

• selectValues -- select part of a hash table
• selectKeys -- select a part of a hash table by keys