Issue with upvars

[qw23]

I’m experiencing an issue regarding upvars. Its application is an update to the Streams library, but I’ll keep it as simple as possible for now. I do hope that someone will find a solution to the version I’m presenting here.

One use of upvars is as a parameter to be used in an embedded script. A well-known example is with the for block, e.g.:

Another example is in the “Iteration, composition” library:

In both cases the upvar (i , or #) is maintained by the HOF-block (for, or cascade ) and used by the embedded command (change) or function (+), respectively. And it works very well.

But if the evaluation of the script is somehow postponed, an issue may arise. I made a block new applicator:

… that will create an anonymous HIGHER ORDER FUNCTION (HOF), applying an embedded function on an index; the latter corresponds with the number of times the HOF was called.

So, for example:

Stand-alone, this works well. But if I create another HOF with the same block, something weird happens:

I can change the name of any upvar, so I can repair it:

… but for a library function, I don’t want the user to have to remember changing upvar names from the default.

So this is my request: can anyone think of a way to prevent this mix-up of upvars?

This links to the project.

[sarpnt]

does index need to be an upvar here? you already call the function with it. why not just create a local variable in the block instead?

[qw23]

Do you mean, something like this: … ?

It works, but it’s also a lot of hassle.

[sarpnt]

that's not what i meant, and i have no clue how that works. when i say you call the function with the variable, i mean you gave it as an input. use the input.

[qw23]

Yeah, that works, too. Still I’d prefer to use upvars for referring to any inputs to the (callback function that are supplied by the block - it’s more intuitive for the user, I think. The approach you’re advocating is (IMO) second-best, so I’ll be using that for now - i.e. until anyone invents a way around the upvars issue, or a more local variety of upvars is introduced. Thanks for thinking with me!