Cascade Expressions: cascade get

Cascade Expressions

There are some places where you may use either literal value or cascade expression. These places are:

• parameter's output cell,
• parameter's input cell,
• domain attribute value,
• input level's property (source value).

There are 2 types of cascade expressions:

• cascade get - redirects evaluation to given parameter,
• cascade call - redirects evaluation to given function.

Basic information about cascade get:

• every cascade get starts with $p symbol, which means cascade to parameter,
• when cascading to parameter, you may pick any output cell you want.

Below you can see 3 basic usages of cascade expressions:

1) Cascade expression inside parameter's output cell:

2) Cascade expression used in domain attribute:

3) Cascade expression used in level source:

Cascade get

Everywhere you use Cascade get expression it redirects evaluation to given parameter and returns value from that parameter from specified output column.

Cascade get syntax

Implicit type conversion

If, within P1 parameter in level of type T1 occurs cascade get to level type T2 in P2 parameter, then:
step 1: internally cascade get will return Holder type T2"
step 2: Holder is converted into Holder

• conversion will meet Hyperon's conversion standards, see dec(), num(), str(), date(), bool() conversion methods,
• conversions may be lossy, which simply means losing the value or precision of a variable. (eg. T1 is integer while T2 is number)
  

Example

Suppose we have 2 parameters defined as follows:

Parameter par.p1:

Parameter par.p2:

As you can see, par.p2 has output level value of type integer and output level factors defined as array of type number.

See what happens when you will get value from par.p2 with risk.code equal to A, B and C:

Result of getting value from par.p2 with risk.code=A in context:

Result of getting value from par.p2 with risk.code=B in context:

Result of getting value from par.p2 with risk.code=C in context:

TIP: When parameter P1 uses cascade get to parameter P2, then P2 is evaluated with the very same context P1 was.

Avoid cycles When using cascade gets it is forbidden to create evaluation cycle. In other words:

Evaluation cycle: P1 -> P2 -> … -> P1 is not allowed.