"> Implementation -- State List

Implementation--
State List and Entries
Variable Change List and Entries

State List and Entries:

The State List holds information concerning variables' states. State list entries reference the variable in the Symbol Table to which the entry applies. They also contain a string representation which is applicable in some way to the value of the variable. Usually, this string in the variable's current value although, in some places, it refers to the new value of the variable. The state list is used primarily in the Search Tree nodes to represent the current state of the simulation.

Variable Change List and Entries:

The Variable Change List is a special state list that holds expressions that evaluate to a new value for the variable referenced instead of the current value of the variable. The expressions are evaluated at the time of execution to come up with a value for the variable. Each evaluation of the expression may come up with a different value depending on the current values of the variables used in the espression. Variable change lists are a part of the Slice List entries expressing the changes in variables occuring in the slice.

Functionality for state lists includes the standard List functions as well as finding program counter variables, finding a given variable, comparing two state lists to see if they represent the same state, copying one state list to another and printing a state list.

Functionality for state list entries includes setting and retrieving the symbol reference and value, getting the symbol's name or type, checking to see if a given symbol's name and type are the ones referenced by the entry, comparing two state list entrys' symbols, copying a state list entry to another state list and printing a state list entry.

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Andrew Tompkins
Beaverton, OR 97006
Last rev: 18 APR 02
URL:
http://home.comcast.net/~andytom/simplan.docs/control/state.list.html

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