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Function Grades
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Infusion

Most grades represent Infusion components - these are derived from the base grade fluid.component. However, some grades describe plain JavaScript functions - these are derived from the base grade fluid.function. The purpose of the Fluid API call fluid.defaults could be understood as providing metadata about some element of the system. In the case of a full component grade, this metadata is sufficient to allow the framework to automatically construct the creator function for the component. In the case of a function grade which describes an already existing function with a global name, the metadata supplies hints to the user about how to call the function and its purpose.

Registering a global function

A global function is registered within infusion at a stable place in its global namespace by working with the core API functions fluid.registerNamespace and fluid.setGlobalValue - in practice the latter is rarely used, in favour of directly setting members on namespace objects.

If you are working in the browser, the global object (traditionally named window) coincides with Fluid's global object (which can be retrieved from fluid.global - assuming that you have already managed to resolve the fluid object itself). If you are working in node.js, you need to make calls to fluid.registerNamespace to bring parts of the global namespace into visibility as variables local to your file.

A typical sequence could look like this:

var examples = fluid.registerNamespace("examples");

examples.linearMap = function (m, x, c) {
    return m * x + c;
}

This registers a global function named examples.linearMap into the global namespace.

Registering defaults for a global function

This function can be used as-is - however, one piece of metadata we could supply it might be an * argument map * allowing it to be invoked with named rather than positional arguments. We could do this as follows:

fluid.defaults("examples.linearMap", {
    gradeNames: "fluid.function",
    argumentMap: {
        "m": 0,
        "x": 1,
        "c": 2
    }
});

Invoking a global function with named arguments

We can then invoke our function using fluid.invokeGradedFunction as follows:

var result = fluid.invokeGradedFunction("examples.linearMap", {
    m: 1.5,
    x: 2,
    c: 1
}); // computes result of 4

This is a small but occasionally useful courtesy - especially when invoking functions from material encoded in configuration rather than in code.

Framework function grades

All of the pure function grades (that is, non-component grades) defined in the framework represent model transformation functions derived from fluid.transformFunction. These grades are fluid.standardInputTransformFunction, fluid.standardOutputTransformFunction, fluid.multiInputTransformFunction, fluid.standardTransformFunction and fluid.lens.