Worp scripts are run in a Lua sandbox. This is simple a separate namespace in the Lua interpreter where code can be loaded without interfering with Worp itself.
Any variables and functions which are not defined local will end up being globals in the sandbox namespace. While globals are usually considered bad practice, they come in handy when using live programming: when new chunks are sent from the editor to Worp they are run in the same sandbox and can access or alter any defined variables.
An instrument in Worp is basically a function which, when called, will start generating sound at the given note and given volume. Calling the same function more than once will play more then one note for polyphonic instruments, and calling the same function for an active note with the volume set to zero will mute the note.
Worp uses midi note numbers for instruments, where 60 is defined as the middle C at 261.6 Hz. Volume is given in the range 0 to 1.
For example, the following code will play the middle C on piano for 1 second at medium volume (assuming the function piano has been defined earlier):
piano(60, 0.8) at(1, function() piano(60, 0) end)
Because Worp is all about playing notes, the 'play()' function is provided as a shorthand. Again playing the middle C for one second:
play(piano, 0.8, 1)
Time in Worp is handled by the event scheduler, which does nothing more than calling functions at a requested time. To schedule a function for future execution, use the built in function at: at(TIME, FUNCTION [, ...])
For example, the following line will print the text "Hello world" after one second:
at(1, function() print("Hello", "world") end)
The 'at()' function has a shorthand notation for functions which are defined globally:
at(1, "print", "Hello", "world")
Worp takes care not to let time slip unexpectedly. Consider the following fragment:
at(1, <i>play</i>, piano, 60, 0.3) at(1, <i>play</i>, piano, 72, 0.3)
If at() would use the current time as reference for scheduling function calls in the future, there would be no guarantee that the two notes would be played at the same time: if any time goes by between the two calls to 'at()', the two calls will be scheduled to run at a different time.
Instead, at() uses another time reference: the time the current function was scheduled to run, even if for some reason the current function was scheduled too early or too late.
The result is that the following code:
function tick() print("tick") at(1, tick) end tick()
is sure to call the tick() function at exact 1 second intervals on average, without introducing additional delay caused by the time needed to run the code.
On top of this function more complex objects such as metronomes and pattern generators can be built.