product(a, attr)
product(a)
Returns the product of the specified attr for tuples in relation a.
If the relation has only one attribute then it is used and no attr need be specified.
Beware projecting over the desired attr instead of passing the attr since these could give very different results when duplicate values are present.
Examples
None
product($S[SNO="S0"], STATUS)1
Some
product($S, STATUS)3600000
Beware, not the same
product($S{STATUS})6000