Hash problems - clashing with newLISP's own symbols

[cormullion]

I'm trying to learn about hash tables (or newLISP's way of doing them). I think I need to learn how to avoid clashes with newLISP's reserved words.



Here's a short test case:

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(context 'hash) ; create hash container

(dolist (the-word (parse "Set the controls for the heart of the sun.
It looks like it's time for a sharp exit, but don't make a hash of it!" " "))
(set 'the-word (lower-case the-word))
(replace "[^A-Za-z]" the-word "" 0) ; tidy the string
(set 'occurrences (eval (sym the-word hash))) ; number of occurrences of word in list
(if (> occurrences 0)
(set (sym the-word hash (+ 1 occurrences))) ; increase count for this word
(set (sym the-word hash ) 1 ) ; or add new word
))
(dolist (s (symbols hash))
(println (sym s hash) ":" (eval (sym s hash))))
(exit)

which gives the output:

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:1
a:1
but:1
controls:1
dont:1
hash:exit:1
hash:for:1
heart:1
it:1
its:1
like:1
looks:1
make:1
occurrences:1
of:1
s:s
hash:set:1
sharp:1
sun:1
the:1
the-word:nil
hash:time:1

invalid function : (hash:exit)


[Lutz]

I haven't looked through the code you posted (sorry I am in a hurry at the moment). But reserved words in a dictionary should work, because they get explicitely overwitten.

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newLISP v.8.7.4 on OSX, execute 'newlisp -h' for more info.

> (set (sym "exit" 'MyHash) 123)
123
> (eval (sym "exit" 'MyHash))
123
>

;; try the new shorter/faster form since 8.7.4
;; with an expanded syntax of 'context'

> (context 'MyHash "time" 456)
456
> (context 'MyHash "time")
456
>


A different problem arises when you save the context (save "myhash.txt" 'MyHash) and then load it again with (load "myhash.txt") with words like 'set'. Because of this in the projects I am invloved (indexing/parsing huge numbers of documents), we prepend every word token with a "_" underscore, but if your dictionaries are never saved to disk this should not be a problem. There must be something different going one here.  



Lutz

[Lutz]

After looking into the code I see the following:



After (context 'hash) you should go back into MAIN doing a (context 'MAIN). If not all the code will be translated under context 'hash.



So just do:

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(context 'hash) ; create hash
(context 'MAIN)

(dolist (the-word ...)


now all your code gets defined and executed under MAIN and will not clash/be overwitten with words going into your dictionary 'hash.



Lutz



ps: your code runs fine after this change

[cormullion]

Thanks again, Lutz. It looks reasonably obvious, in hindsight, but problems look harder before you see their solution!

[cormullion]

OK, now I've got a nice big 'hash' table. Is there an easy way to sort them by value?



HASH:a 1

HASH:a 3

HASH:a 2



=>



HASH:a 3

HASH:a 2

HASH:a 1



Otherwise I'll have to go through and create an array, I think...