I have tried this out but I am not able to see any difference between those. Can some one explain the difference with an example that would be very helpful:
By definition:
$:: - literally referring to the selection made in the field in the $state.
P() - all possible (p) values of the field in the$ state
Set Modifiers with implicit field value definitions
In the above examples, all field values have been explicitly defined or defined through searches. There is however an additional way to define a set of field values by the use of a nested set definition.
In such cases, the element functions P() and E() must be used, representing the element set of possible values and the excluded values of a field, respectively. Inside the brackets, it is possible to specify one set expression and one field, e.g. P({1} Customer). These functions cannot be used in other expressions:
Examples:
sum( {$<Customer = P({1<Product={‘Shoe’}>} Customer)>} Sales ) returns the sales for current selection, but only those customers that ever have bought the product ‘Shoe’. The element function P( ) here returns a list of possible customers; those that are implied by the selection ‘Shoe’ in the field Product.
sum( {$<Customer = P({1<Product={‘Shoe’}>})>} Sales ) same as above. If the field in the element function is omitted, the function will return the possible values of the field specified in the outer assignment.
sum( {$<Customer = P({1<Product={‘Shoe’}>} Supplier)>} Sales ) returns the sales for current selection, but only those customers that ever have supplied the product ‘Shoe’. The element function P( ) here returns a list of possible suppliers; those that are implied by the selection ‘Shoe’ in the field Product. The list of suppliers is then used as a selection in the field Customer.
sum( {$<Customer = E({1<Product={‘Shoe’}>})>} Sales ) returns the sales for current selection, but only those customers that never bought the product ‘Shoe’. The element function E( ) here returns the list of excluded customers; those that are excluded by the selection ‘Shoe’ in the field Product.
I think that the difference lies on that P() can do indirect searches, not just only the current selections.
