I'm interfacing with WordNet, and some of the terms I'd like to classify (various proper names) are capitalised in the database, but the input I get may not be capitalised properly. My initial idea here is to write a predicate that produces the various capitalisations possible of an input, but I'm not sure how to go about it.
Does anyone have an idea how to go about this, or even better, a more efficient way to achieve what I would like to do?
It depends on what Prolog implementation you're using, but there may be library functions you can use.
e.g. from the SWI-Prolog reference manual:
4.22.1 Case conversion
There is nothing in the Prolog standard for converting case in textual data. The SWI-Prolog
predicates code_type/2 and char_type/2 can be used to test and convert individual
characters. We have started some additional support:
downcase_atom(+AnyCase, -LowerCase)
Converts the characters of AnyCase into lowercase as char_type/2 does (i.e. based on the
defined locale if Prolog provides locale support on the hosting platform) and unifies the
lowercase atom with LowerCase.
upcase_atom(+AnyCase, -UpperCase)
Converts, similar to downcase_atom/2, an atom to upper-case.
Since this just downcases whatever's passed to it, you can easily write a simple predicate to sanitise every input before doing any analysis.
Related
Being new to prolog I am reading existing code (as well as trying to write some code). Having some prior background in semweb I started to play with it and see something that is confusing me. Example assertion:
?- rdf_assert(ex:bob, rdf:type, foaf:'Person').
I also did find the following in the documentation:
Remember: Internally, all resources are atoms. The transformations
above are realised at compile-time using rules for goal_expansion/2
provided by the rdf_db library
Am I correct in assuming that somehow the library is treating the three URIs as atoms? I thought that the compiler would treat this as module_name:predicate, but that does not seem to be the case. If that is true, could you please provide a simple example on how this could be done in prolog?
Thanks
Prolog is not a functional language. This implies 2+3 does not evaluate to 5 and is just a term that gets meaning from the predicate that processes it. Likewise, ex:bob is just a term that has no direct relations to modules or
predicates. Only predicates such call/1 will interpret this as "call bob in the module ex".
Next to that, (SWI-)Prolog (most Prolog's, but not all) have term expansion that allows you to rewrite the term that is read before it is handed to the compiler. That is used to rewrite the argument of rdf/3: each appearance of prefix:local is expanded to a full atom. You can check that by using listing/1 on predicates that call rdf/3 using the prefix notation.
See also rdf_meta
I have a list which holds some string values.
A = [John, goes, to, party].
How can I pass this text to speech?
Can any one tell me how to do text to speech conversion in prolog?
Check out the cowsay pack. pack_install(cowsay). Look at the 'add-ons' page on SWI-Prologs website.
You will need to use the foreign language interface of your Prolog system to call an external API that does the speech synthesis. Prolog foreign language interface are not standard but Prolog system specific. Thus, without further details, is not difficult to give you more specific advise.
UPDATE: An alternative solution to the use of the foreign language interface is for the Prolog process to write the strings to standard output and to use a shell pipe to pass those strings to the Python process that reads those strings from standard input.
Whenever I see a Julia macro in use like #assert or #time I'm always wondering about the need to distinguish a macro syntactically with the # prefix. What should I be thinking of when using # for a macro? For me it adds noise and distraction to an otherwise very nice language (syntactically speaking).
I mean, for me '#' has a meaning of reference, i.e. a location like a domain or address. In the location sense # does not have a meaning for macros other than that it is a different compilation step.
The # should be seen as a warning sign which indicates that the normal rules of the language might not apply. E.g., a function call
f(x)
will never modify the value of the variable x in the calling context, but a macro invocation
#mymacro x
(or #mymacro f(x) for that matter) very well might.
Another reason is that macros in Julia are not based on textual substitution as in C, but substitution in the abstract syntax tree (which is much more powerful and avoids the unexpected consequences that textual substitution macros are notorious for).
Macros have special syntax in Julia, and since they are expanded after parse time, the parser also needs an unambiguous way to recognise them
(without knowing which macros have been defined in the current scope).
ASCII characters are a precious resource in the design of most programming languages, Julia very much included. I would guess that the choice of # mostly comes down to the fact that it was not needed for something more important, and that it stands out pretty well.
Symbols always need to be interpreted within the context they are used. Having multiple meanings for symbols, across contexts, is not new and will probably never go away. For example, no one should expect #include in a C program to go viral on Twitter.
Julia's Documentation entry Hold up: why macros? explains pretty well some of the things you might keep in mind while writing and/or using macros.
Here are a few snippets:
Macros are necessary because they execute when code is parsed,
therefore, macros allow the programmer to generate and include
fragments of customized code before the full program is run.
...
It is important to emphasize that macros receive their arguments as
expressions, literals, or symbols.
So, if a macro is called with an expression, it gets the whole expression, not just the result.
...
In place of the written syntax, the macro call is expanded at parse
time to its returned result.
It actually fits quite nicely with the semantics of the # symbol on its own.
If we look up the Wikipedia entry for 'At symbol' we find that it is often used as a replacement for the preposition 'at' (yes it even reads 'at'). And the preposition 'at' is used to express a spatial or temporal relation.
Because of that we can use the #-symbol as an abbreviation for the preposition at to refer to a spatial relation, i.e. a location like #tony's bar, #france, etc., to some memory location #0x50FA2C (e.g. for pointers/addresses), to the receiver of a message (#user0851 which twitter and other forums use, etc.) but as well for a temporal relation, i.e. #05:00 am, #midnight, #compile_time or #parse_time.
And since macros are processed at parse time (here you have it) and this is totally distinct from the other code that is evaluated at run time (yes there are many different phases in between but that's not the point here).
In addition to explicitly direct the attention to the programmer that the following code fragment is processed at parse time! as oppossed to run time, we use #.
For me this explanation fits nicely in the language.
thanks#all ;)
I'm new to Prolog and to logic paradigm development, but I think this can help me in my application. My first doubt is what can I do this with the language.
I'm doing some text processing/natural language processing and I think that my code will be clearer and easy doing it in a logical language than in Java (that is what I'm using and will integrate with Prolog).
My first goal now is discover the char type of a String (alphabetic, digit, numeric, etc...). I have four mais arguments: hasLetter, hasDigit, hasSymbol, hasPunctuation.
With Prolog, I can have one method determineType() that will return me the type based on this four attributes or it only with single tests, thinkgs like isDigit(), isAlphabetic(), etc?
The category or "type" of each character is a relation, relating a character to its type. You can code it in Prolog using a predicate. A meaningful name for such a predicate would for example be: "character_type(C, T)". In SWI-Prolog, check out the library predicates char_type/2 and code_type/2 to get this information. You can use them for obtaining the type(s) of a character (on backtracking, alternative solutions may be generated) as well as for testing whether a character belongs to a supplied category. For language processing, you may also find definite clause grammars (DCGs) useful.
The use of symbol literals is not immediately clear from what I've read up on Scala. Would anyone care to share some real world uses?
Is there a particular Java idiom being covered by symbol literals? What languages have similar constructs? I'm coming from a Python background and not sure there's anything analogous in that language.
What would motivate me to use 'HelloWorld vs "HelloWorld"?
Thanks
In Java terms, symbols are interned strings. This means, for example, that reference equality comparison (eq in Scala and == in Java) gives the same result as normal equality comparison (== in Scala and equals in Java): 'abcd eq 'abcd will return true, while "abcd" eq "abcd" might not, depending on JVM's whims (well, it should for literals, but not for strings created dynamically in general).
Other languages which use symbols are Lisp (which uses 'abcd like Scala), Ruby (:abcd), Erlang and Prolog (abcd; they are called atoms instead of symbols).
I would use a symbol when I don't care about the structure of a string and use it purely as a name for something. For example, if I have a database table representing CDs, which includes a column named "price", I don't care that the second character in "price" is "r", or about concatenating column names; so a database library in Scala could reasonably use symbols for table and column names.
If you have plain strings representing say method names in code, that perhaps get passed around, you're not quite conveying things appropriately. This is sort of the Data/Code boundary issue, it's not always easy to the draw the line, but if we were to say that in that example those method names are more code than they are data, then we want something to clearly identify that.
A Symbol Literal comes into play where it clearly differentiates just any old string data with a construct being used in the code. It's just really there where you want to indicate, this isn't just some string data, but in fact in some way part of the code. The idea being things like your IDE would highlight it differently, and given the tooling, you could refactor on those, rather than doing text search/replace.
This link discusses it fairly well.
Note: Symbols will be deprecated and then removed in Scala 3 (dotty).
Reference: http://dotty.epfl.ch/docs/reference/dropped-features/symlits.html
Because of this, I personally recommend not using Symbols anymore (at least in new scala code). As the dotty documentation states:
Symbol literals are no longer supported
it is recommended to use a plain string literal [...] instead
Python mantains an internal global table of "interned strings" with the names of all variables, functions, modules, etc. With this table, the interpreter can make faster searchs and optimizations. You can force this process with the intern function (sys.intern in python3).
Also, Java and Scala automatically use "interned strings" for faster searchs. With scala, you can use the intern method to force the intern of a string, but this process don't works with all strings. Symbols benefit from being guaranteed to be interned, so a single reference equality check is both sufficient to prove equality or inequality.