I'm trying to replicate the interface of some MATLAB code I use frequently. Because functions in MATLAB have knowledge of their "output arguments", different behaviors can occur if an assignment is used or not (i.e. `a = foo()` can do something different than just `foo()`). Specifically, the interface I'm trying to replicate displays a plot with no output arguments, and otherwise returns the data.
In Python, I'd use a kwarg `plot=False`. What's the most Julian way of doing this? I have two thoughts right now: 1. Use a kwarg. `foo(...)` returns the data, `foo(..., plot=true)` creates a plot and returns nothing (or the plot handle?). 2. Create a `@plot` macro that sets a global `PLOT` boolean variable. This indicates to the functions it's configured to work with that the data should be plotted. The use would be: `@plot foo(...)`, which generates the code: ``` PLOT = true foo(...) PLOT = false ``` This could also be modified to return the plot handle at the end of the block. While I tend to like this interface more than #1, it's also more magical, which is bad. 3. Create a `@plot` macro that somehow knows how to plot each function (a registry of some kind?). Then the function needs no knowledge of how to plot itself, and the macro is just a fast way of writing in the plotting code. Use is `@plot foo(...)`, which expands to ``` data = foo(...) plotting code here... ``` 4. Create a separate function `fooplot`. `foo` returns the data. `fooplot` runs foo, and creates a plot. Out of all of these, I like option #3 best, but want to use the most Julian way of doing things as possible. Thoughts? ------ Also, is there a good way to only load the plotting package (Gadfly, Winston, etc...) when it's first used? Loading these takes a long time; it would be nice if they could only be loaded upon the first call to `plot`.
