Detect and complain if the same symbol is used for two or more concepts within the same document

[smiths]

This issue came up during the discussion in #1901.

Symbols are routinely used for different meanings in science and engineering. However, if the same symbol has more than one meaning in the same document, this is a problem. Drasil should prevent the user from making this mistake by automatically detecting if a symbol is use for more than one purpose within the same document.

[muhammadaliog3]

@smiths
do you know how to convert a sentence to a string. I need it because the error function in Haskell must have an argument of type string.

[smiths]

I'm sorry @muhammadaliog3, but I do not know the answer to your question. Maybe you can find it by looking at the code documentation:

https://jacquescarette.github.io/Drasil/docs/index.html

Alternatively, this is likely a question that @JacquesCarette or @bmaclach could answer.

[JacquesCarette]

First, you should really investigate if that Sentence is crucial, i.e. if it is inevitable that the only information you have, when you're ready to throw that error, is a Sentence. Often, it is not, and then printing is simplified.

If it is, then there are various 'rendering' functions in drasil-printer. You'll need to use the plain printer.

If you tell us the context more precisely, we can direct you to the proper functions. Often, wishing to print a Sentence is actually a sign that you're not quite doing the right thing. [And sometimes, it's a design bug in Drasil.]

[muhammadaliog3]

@JacquesCarette
I guess this is a good time to present my solution.
Say we have the the following rows in a symbols table
[(sigma, description_1),(sigma, description_2),(E, discription_3),(E, description_4)]
Here two variables have the conflicting symbol of sigma and 2 have conflicting symbol of E.

I do not believe that in the error we should simply print "Duplicate symbols found", rather we should at the very least say "Duplicate symbols found. See the following descriptions: (description_1,description_2,description_3,description_4)".

These descriptions are stored as a list of sentences. I can fold the sentences into one sentence, but to print the error I still need to convert that one sentence to a string. This is the code by the way, the line with ----HERE------------ is where I print the error.

table :: (Quantity s, MayHaveUnit s) => Stage -> [s] -> (s -> Sentence) -> LabelledContent
table st ls f
    |noDuplicate = llcc symbTableRef $
      Table [atStart symbol_, atStart description, atStart' unit_]
      (mkTable [P . (`symbol` st), f, toSentence]
      $ filteredChunks)
      (titleize tOfSymb) True
    |otherwise = error $ "Duplicate Symbols" ++ foldlSentCol descDuplicates ---HERE----------------
    where 
        filteredChunks = filter (`hasStageSymbol`st) ls
        symbolsCol = map (P . (`symbol` st)) $ filteredChunks
        descCol    = map (f)                 $ filteredChunks
        symDescPair = zip symbolsCol descCol
        symDuplicates = symbolsCol \\ (nub symbolsCol) --if you did not know (\\) is the difference between lists
        noDuplicate = symDuplicates == []
        descDuplicates = [snd x | x <- symDescPair, fst x `elem` symDuplicates]

[JacquesCarette]

That's a nice piece of Haskell. I would prefer if the error was even more verbose & precise: it should give an error for each UID/symbol/description tuple that is duplicate. So an error for (sigma, description_1),(sigma, description_2) and another for (E, discription_3),(E, description_4).

[muhammadaliog3]

But to print the errors you mentioned I would need to convert a sentence to a string. I still do not know how to do that.

[JacquesCarette]

Oh, because of the descriptions? Ok, skip those. Just do the UIDs and symbols then.