Expression PropertyPublished string
The expression to be evaluated.
Value PropertyPublicRead Only extended
The resultant value of the expression.
IsBuiltIn FunctionPublic (FuncName: string): boolean
Determines whether the argument is a recognised built-in function.
NamedValues PropertyPublished TssNamedValues
A structure for holding named values, often constants such as pi and e, but it can hold any values that you want.
OnGetValue PropertyPublished TssGetValueEvent
An event called to retrieve the value of a user-defined variable. For example, if the expression was 2 * A then this event would be called to retrieve the value of A (unless A was pre-defined in the list of NamedValues.
OnChange PropertyPublished TNotifyEvent
Invoked when the expression is changed.


This type allows the definitions of constants and frequently used variables.

Add ProcedurePublic (name: string; value: extended)
Adds a named value. Will first delete any existing value with the same name.
Delete ProcedurePublic (name: string)
Deletes a named value. Performs no action if the name is not present.
Clear ProcedurePublic ()
Deletes all named values.
IndexOf FunctionPublic (name: string): integer
Returns the index of a value from its name. Returns -1 if the value is not present.
Assign ProcedurePublic (Source: TPersistent)
Copies a second TssNamedValues to the current one.
BeginUpdate ProcedurePublic ()
Starts buffering changes. The OnChange event will not be called until EndUpdate has been called for each time BeginUpdate was called.
EndUpdate ProcedurePublic ()
Finishes buffering changes. EndUpdate should be called once for each BeginUpdate.
IsValidName FunctionPublic (name: string): boolean
Determines whether name is valid. Only alphanumeric and underscore characters are allowed in value names.
ValueByName PropertyPublicRead Only [name: string]: extended
A value from its name.
ValueByIndex PropertyPublicRead Only [index: integer]: extended
A value from its index.
Values PropertyPublicRead Only [index: integer]: TssNamedValue
The array of named values.
Count PropertyPublicRead Only integer
The number of named values defined.
OnChange PropertyPublished TNotifyEvent
Invoked when the value is changed.
CaseSensitive PropertyPublished boolean
Whether named values should be case-sensitive or not, e.g. whether variables PI and pi should be considered different or the same.


TssGetValueEvent procedure(Sender: TObject; Identifier: string; var Value: extended; var Undefined: boolean) of object
EssExpressionError An exception raised if the expression contains an error.