need help understanding letex

[ghyll]

[ghyll]

[Lutz]

[ghyll]

I’m new to programming, so I don’t know how one programs in Scheme or other traditional LISP implementations.

Thanks for the help with streams! Using contexts with push/pop seems like a much easier way to manage the streams than trying to manipulate letex and expand for each function.

I’d still like to understand and master letex. I was told the error message is because I’m using letex incorrectly in my `product-stream-Reuler` function (included in my original question). It seems (from the error message) that still I don’t quite understand it. I’ve read the manual and the wikibooks, and spent time playing around with the code, and no lightbulbs are going off. Am I using the wrong syntax? Am I using the correct syntax incorrectly? Or is that specific error message due to a problem somewhere else in my code?

[ralph.ronnquist]

Or maybe you're using too many single-quotes in that function?

[ghyll]

Were you referring to a specific part?

Without the single quotes, the newLISP interpreter tries to evaluate the streams using implicit indexing. This doesn't work, because (for example) there is no 998th list item in `(998 (lambda () (enum-interval-descending (- 998 1) 100)))`

http://www.newlisp.org/downloads/newlis ... rest_slice

I''ll run through the code again to make sure all of the quotes are necessary. Thanks for the suggestion.

[ralph.ronnquist]

I can't say I've gone too deep into the code, and generally as always, it's better to follow Lutz' advice. It just looked to me like there where all too many single quotes in the function; e.g. the sub expression (product-stream (num-stream 'a1) 's2) will eventually invoke the product-stream function with the second argument being the symbol s2, which then, in that function, is assigned to be the value of s2. This (unless the first argument is an empty stream) results in empty-stream? being called with a symbol whose value is a symbol (namely s2) as argument, and thus, the primitive empty? is called with that symbol as argument. Which was the basis for my rather off-handed remark.

[itistoday]