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[REBOL] Re: Binding operators

From: fsievert::uos::de at: 10-Sep-2001 9:06

> On Sunday 09 September 2001 01:26, Frank Sievertsen wrote: > > -> When there is an operator-word, but it does not hold an operator, the > > interpreter will throw an error. > > If the interpreter always throws an error when an operator word is not > actually an operator then the 'and' argument to the reportA function should > fail as well, should it not? > > I've tried another test and it looks like the operator word will only work as > the first argument to a function.
There = behind an evaluated value. The interpreter is looking for op!s, after it evaluted something. One example: reporta -> function -> searching for one argument reporta and -> evaluating and (integer!) -> looking if there is an op!-word folliwing, no evaluating reporta. But: reportc -> function -> searching for one argument reportc 9 -> evaluating 9 -> looking if there is an op!-word following, YES: reportc 9 and -> invalid operator and! It has nothing to do with "second" or "first" argument. Example: reportc (9) (and) should work, because there is no following op!-word. And (9 and) will fail.
> > I'm afraid infix operators are almost a kludge in REBOL. Words > > such as +, *, AND etc. are probably handled before the actual > > execution. > > Yeah, that's what I've done with my own scripting language. I move the > operator to make it prefix for the interpreter. REBOL must work a little > differently otherwise none of the report functions would work, but perhaps > the infix fiddling interacts badly with the argument fetching.
The reason, why 'and works as an prefix, too, is that op!s are any-function!s, too. They are not handled as an op!, but as an any-function! in that case. I don't see a bug here, but I think it is not a good idea to detect op!s by the word! that holds them. It would be better (but slower) to detect them by the datatype!. CU, Frank