applyKeys -- apply a function to each key in a hash table

Synopsis

• Usage:

  applyKeys(H, f)

  applyKeys(H, f, g)

• Inputs:
  • H, a hash table,
  • f, a function, of one argument
  • g, a function, of two arguments, for collision handling
• Outputs:
  • a hash table, obtained by applying f to each key in H

Description

i1 : H = new HashTable from {1 => 10, 2 => 15, 3 => 20}

o1 = HashTable{1 => 10}
               2 => 15
               3 => 20

o1 : HashTable

i2 : applyKeys(H, k -> k + 100)

o2 = HashTable{101 => 10}
               102 => 15
               103 => 20

o2 : HashTable

i3 : applyKeys(H, k -> k//2, max)

o3 = HashTable{0 => 10}
               1 => 20

o3 : HashTable

i4 : applyKeys(H, k -> k//2, plus)

o4 = HashTable{0 => 10}
               1 => 35

o4 : HashTable

Caveat

See also

• hash tables
• applyPairs -- apply a function to each pair in a hash table
• applyValues -- apply a function to each value in a hash table
• keys -- keys used in a hash table, dictionary, or database
• scanKeys -- apply a function to each key in a hash table or database