.OmegahatExpression: Execute an Omegahat/Java expression

Description

This evaluates the specified expression in the Omegahat sub-system, resolving references from the Omegahat databases and the list of arguments provided in this call.

This is no longer active in the current version (0.69-0) of the package. This is done to avoid a dependency on an older version of ANTLR. If this feature is needed, use .Java instead or please ask for it to be reintroduced.

Usage

.OmegahatExpression(expr, ..., .name=NULL, .sigs="", .convert = TRUE)

Arguments

expr

A string value that is a valid Omegahat expression.

...

a collection of named arguments which are converted to Java objects and available to the Omegahat expression when it is evaluated using the names of the arguments.

.name

The name to use to store the result in the omegahat named reference database. If this is missing, an anonymous reference is returned or the value converted to an R object. If the result of the Java method can be converted, this argument can be used to prohibit this conversion and leave the Java value in Omegahat for use in future .Java calls.

.sigs

not really needed here, but can be used to control the conversion of the arguments in ...

.convert

logical value indicating whether the Omegahat interpreter should attempt to convert the result of the expression to an R object (TRUE), or alternatively just assign the value to a local database and return a reference. This is useful when one wishes to avoid converting an object back to its R counterpart because you wish to use it in subsequent .OmegahatExpression or .Java calls.

Value

The result of the Omegahat evaluation of the expression, converted from a Java object to an R object using the basic and extensible conversion mechanism between Java and R.

Details

This can be used to create functions, assign multiple values in a single call, create arrays easily, etc. One of the drawbacks of using this is that the details of the Omegahat and Java languages are exposed to the code that calls them in this manner. By using the .Java and .JavaConstructor functions, one can easily subsititute different implementations that for example, use CORBA to invoke methods in remote objects written in different languages. \ In some ways, this has similarities to substitute.

Examples

Run this code

 .OmegahatExpression("show(1::10)")
 .OmegahatExpression("show(1::z);", z=10)