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scanKeys -- apply a function to each key in a hash table or database

Usage:

scanKeys(t, f)
Inputs:
- t, a hash table, or Database
- f, a function,

Description

scanKeys(t, f) applies the function f to each key in the hash table t.

i1 : t = hashTable {{1,8},{2,20},{3,4},{4,20}}

o1 = HashTable{1 => 8 }
               2 => 20
               3 => 4
               4 => 20

o1 : HashTable

i2 : scanKeys(t, print)
1
2
3
4

i3 : scanKeys(t, k -> if k>2 then print t#k)
4
20

Caveat

This function requires an immutable hash table. To scan the keys in a mutable hash table, use scan(keys t, f).

See also

hash tables
applyKeys -- apply a function to each key in a hash table
keys -- keys used in a hash table, dictionary, or database
scan -- apply a function to each element in a list or sequence
scanPairs -- apply a function to the pairs in a hash table
scanValues -- apply a function to each value in a hash table or database

Ways to use scanKeys:

scanKeys(Database,Function)
scanKeys(HashTable,Function)

For the programmer

The object scanKeys is a method function.

The source of this document is in Macaulay2Doc/ov_hashtables.m2:575:0.