NULLITY

▶ NULLITY

If a programmatic component does not have a value, it is said to be NULL. But in Tyl its meaning is extended to mean also not exist or does not have items.

Nullity of Tyl Components

Scalar

does not have value

List

list is empty

Record

record does not have any key

Record Key

record key does not exist

Nullity check in Tyl is implemented by null system function:

print 'scalar:'

print null a

print 'assign value'

a 1

print null a

print 'list:'

data [ ]

print null data

print 'add item'

data <- 1

print null data

print 'clear list'

data ->->

print null data

print 'record:'

rec { }

print null rec

print 'add key with value'

rec ◄ 1 'a'

print null rec

print null rec 1

print 'add key without value'

rec ◄ 2

print null rec 2

scalar:
true
assign value
false

list:
true
add item
false
clear list
true

record:
true
add key with value
false
false
add key without value
true