num: 10
num: - 5

ok num is 5

num: -3

ok num is -3

num: +3

ok num is 3

num = * 10

ok num is 30

num: / 10

ok num is 3


val: false
val: or 'value'

ok val is 'value'

val = and 'other'

ok val is 'other'


val: null
val: ? 'value'

ok val is 'value'


val: 6
val: -(10)

ok val is -10

val: - (10)
ok val is -20