The recursion is not the relevant point for your question " how do outputs propagate ". When I remove the recursion from the example, the "propagation" becomes more obvious. The situation of the outermost call then is: class predicates add1 : (integer*, integer* [out]). clauses add1([], []). % this ...

What you call "assignment" and "comparison" is in Visual Prolog (and any Prolog) accomplished by nothing else but the unification of terms. Formally speaking: A variable can be, and can only be, bound by a unification of terms. A unification can succeed or fail. Binding a variable to a value in a un...

@Chris: For the learning curve check the implementation of fromMsStringSeq/1-> in windowsAPI.pro, it is done there more efficient than in my code.

ah, thank you Thomas! So, we should do it like class predicates getLogicalDriveStrings : (charCount BufLen, unsigned Result [out]) -> string_list Str_list. clauses getLogicalDriveStrings(BufLen, Result) = windowsAPI::fromMsStringSeq(uncheckedConvert(windowsAPI::msStringSeq, Buf)) :- Buf = memory::al...

Maybe there is a problem in memory::getString/2-> . Because when I replaced it by my own version, it has worked out: open core class predicates getLogicalDriveStrings : (charCount BufLen, unsigned Result [out]) -> string_list Str_list. clauses getLogicalDriveStrings(BufLen, Result) = getLogicalDrive...

To track the computation you could (besides using the debugger) simply insert calls to write into the code which will produce a 'log'. To try that paste the below in file main.pro of a new console project: class listmanager predicates add1 : (integer*, integer* [out]). end class listmanager %--- imp...

That means, variables can be bound solely through the head of a called clause, without having to use " = ". Like for example in: class predicates inverse : (integer, integer [out]). clauses inverse(Num, -Num). clauses run() :- inverse(3, X), stdio::write("X = ", X). Predicate inverse /2 contains no ...

The conceptual behavior, which Thomas has explained in particular, is also described in the Language Reference in general. It often helps me to look up things there. The reference says that unification takes place in two different situations: When a predicate is called the arguments from the call ar...

Hi Kim, very different Prolog implementations exist. Only some of them are modular within a framework of object-oriented programming. Visual Prolog gives a fine example of objects and modules in a programming language. It comes with a programming environment for developing programs. The environment ...

In my class bitAddOn I give all bit counts type positive or in some cases positiveOptional . For example I have predicates getLowBitPos64 : (unsigned64 X) -> positiveOptional BitPosition. % @short Returns the position of the lowest 1-bit % @end where a result of -1 means that there is no 1-bit in X ...

Hello Harrison, defining domain expressionDOM in the face interface it works without the helper class: interface face domains expressionDOM = smiling; frowning. predicates setExpression : (expressionDOM). getExpression : () -> expressionDOM. end interface face %--- class face : face constructors new...

I recommend however that you keep using the old style syntax for bitwise and boolean operators in build 905. The new syntax has an issue in 64bit mode which affects bitCount64/1-> . For example try this in 32bit and 64bit modes: constants m1 : unsigned64 = 0x5555555555555555. m2 : unsigned64 = 0x333...

Hi choibakk, Wikipedia gives instructions how you can code a trailingZeroBits/1-> function for 64 bits: constants m1 : unsigned64 = 0x5555555555555555. m2 : unsigned64 = 0x3333333333333333. m4 : unsigned64 = 0x0F0F0F0F0F0F0F0F. class predicates bitCount64 : (unsigned64 Value) -> unsigned64 Count. cl...

I happened to see another case of the issue in build 905. When I tried to save the changes in an implementation file I got exactly same error box as posted before. It seems the issue is provoked by certain amounts of lines and characters. I have constructed the attached dummy file TestFile.pro of ab...

Hi Klim (and Thomas), the short answer is: Your code throws a syntax error in Visual Prolog (build 904) and does not work at all. More in detail, I have tried to fit the code into VIP's syntax (which differs from 'standard' Prolog) and let it do a computation which makes sense in somehow. To test my...