the language module's instance of the class

Parameter mapping list. This is a list of lists: [name, func], where 'name' is the parameter name (as a string), and 'func' is the expansion handler function.

The parameter name must be all lower case. During expansion, we convert the first space-delimited token within the {curly brace} parameter string to lower case, then look for an entry in the list with the matching parameter name. If we find an entry, we call its handler function.

The handler function is a pointer to a function that takes two arguments: func(params, ctx), where 'params' is the list of tokens within the {curly braces} of the substitution string, as a list of strings, where each string is a space-delimited token in the original {curly brace} string; and 'ctx' is the MessageCtx object for the expansion. The function returns a string giving the expansion of the parameter.

The parameter list must be provided by the language module, since each language's list of parameters and expansions will vary.

Parameter lookup table. This maps a parameter name to its handler function.

Some parameters expand to properties of objects involved in the command. cmdInfo() makes it easier to define the expansion functions for such parameters. We search the parameters for a Command object, and if we find it, we retrieve a particular source object and evaluate a particular property on the source object to get the result string.

For example, {the dobj} could be handled via cmdInfo('ctx, dobj', &theName, vSubject): we find the current 'dobj' object in the Command, then evaluate the &theName property on that object.

'ctx' is the MessageCtx object with the current sentence context.

'src' is the source object in the Command. This can be given as a property pointer (&actor, say), in which case we simply evaluate that property of the Command object (cmd.(src)) to get the source object. Or, it can be a string giving a NounRole name (dobj, iobj, acc), in which case we'll retrieve the current object for the noun role from the Command. Or, it can be a string with a number, in which case we'll use the number as an index into the argument list.

'objProp' is the property of the source object to evaluate to get the expansion string.

'role' is vSubject if this is a noun phrase with subject usage (in most languages, this is a noun phrase in the nominative case; in English this is called subjective case). It's vObject for any other noun phrase role (direct object, prepositional object, etc). If the role isn't clear from the context (the case marking of the parameter, or the position), use vAmbig to mark it as ambiguous.

construction - build the lookup table

Expand a parameter string. 'ctx' is a MessageCtx object with the current sentence context. This contains the message expansion arguments (ctx.args), the Command object from the arguments (ctx.cmd), and information on the grammar elements of the sentence. 'params' is the list of space-delimited tokens within the curly-brace parameter string. Returns the string to substitute for the parameter in the message output.

if anything went wrong, return nil to indicate we failed to find an expansion