BasicList # ZZ -- get value from list, hash table, database, or string

Synopsis

Operator: #
Usage:

x#i
Inputs:
- x, a basic list, a list, hash table, or string
- i, an integer, an index or key

Description

If x is a list, x#i returns the ith element of x. The entries of the list are numbered starting with 0. If i is negative, then the entries are numbered ending with -1. If i is out of range, an error is signaled.

i1 : L = {a, b, c, b, a};

i2 : L#2

o2 = c

o2 : Symbol

i3 : L#-2

o3 = b

o3 : Symbol

If x is a hash table or database, x#i provides the value associated with the key i.

i4 : T = new HashTable from {a => 103, b => 89.4, c => 92};

i5 : T#a

o5 = 103

i6 : T#b

o6 = 89.4

o6 : RR (of precision 53)

If x is a string, x#i provides the ith character of x, if there is one. Negative indices are counted backward from the end, as with lists. If i is out of range, an error is thrown.

i7 : s = "a perfectly adequate example of a string";

i8 : s#2

o8 = p

i9 : s#-2

o9 = n

Assignment to x#i can change x if x is mutable.

i10 : V = new MutableHashTable from T;

i11 : V#a = 5;

i12 : V#d = 22.3;

i13 : peek V

o13 = MutableHashTable{a => 5   }
                       b => 89.4
                       c => 92
                       d => 22.3

Ways to use this method: