The TAG system

As mentioned above, the tagging system is what makes ReqTools very expandible, without having to change the APIs every day. The tagging system is flexible and offers also better code readability, since all values you'll pass using tagging system are preceded by the attribute name.

To better understand its features, suppose you have a function like this one:

it is a very complex function, with a lot of parameters. Almost for sure, each time you'll have to use it you'll go for the function prototype or for a line in your code already using that function for a quick help reminding all params and their right order. And there's more: once you realized that you also need the zpos parameter in you function call, you'll have to add yet another param, breaking compatibility with old code. (Please, keep in mind that this is just an example...)

Using the tagging system, you should have a function prototype like this one:

well... it is much better. But how would you pass all the parameters to the new function? The answer is simple: by using tagging system.

All you have to do pass all parameters followed by their value and separated by commas, one at a time, like this:

draw_3d_sphere ( env, SPHERE_TAG_SLICES, 10, SPHERE_TAG_RADIUS, 5, SPHERE_TAG_COLOR, &col, SPHERE_TAG_XPOS, x, SPHERE_TAG_YPOS, y, SPHERE_TAG_ZPOS, z, SPHERE_TAG_END );

As you can see there are many advantages:

• Tags can be specified in any order

  You do not have to follow the standard order of a function call, since each parameter is processed by its own.

• Some tags (parameters) can be omitted

  You do not have to pass all params everytime (unless the documentation of a particular TAG is saying so). The tagging system is like a state machine and it will use the last valid value inserted for all following calls to draw_3d_sphere.

• Tags can be added without break old code

  As you should notice, we have used a tag to specify the z-position of our 3D sphere. As our old function prototype remind us, we didn't design the z-pos attribute at the very early stage of library design, but using the tagging system we can always add new tags when there is need to: without breaking old code compatibility.

• Tags enhance code readability

  Last but not least, tagging system enhance code readability because you can see what a particular variable is actually setting in a function call.