Hi Craig - thanks for the reply. Yes, that’s what I’m having to do - but since my app allows the user to write formulae directly, I need to cheat so the user writes
ln(x) and I intervene and redirect this to my adjusted version of the function, myLn. Luckily at the heart of the my app is a parser which can host this intervention, so it’s almost OK - as long as the user doesn’t take the option to look at the parser output. Still, it would have been nice to be able to redefine it: of course, if I did that I would either have to recode the fundamentals of the original function or somehow access it despite having replaced it from the point of view of the outside world. Graham > On 5 Jan 2015, at 15:41, dunb...@aol.com wrote: > > Graham > > > I thought the ability of HC to allow this was a plus. The best example was > the "round" function, which, with a ".5" in the decimal portion of an > argument, alternately rounded the integer portion up or down depending on > whether that integer was odd or even. > > > Most people, like me, intercepted that function, and always rounded a ".5" > up, like I was taught. > > > Anyway, when you ask for a "trick", why not just create "myLn". After all, > you are the author. > > > Craig > > > > -----Original Message----- > From: Graham Samuel <livf...@mac.com> > To: How to use LiveCode <use-livecode@lists.runrev.com> > Sent: Mon, Jan 5, 2015 7:55 am > Subject: Is there a way to replace a built-in function? > > > On the face of it, it’s impossible to replace a built-in function in LC. For > example, take the function ln(x) - that’s natural logarithm. I’d like to > redefine ln(x), but I can’t because the compiler won’t let me use a reserved > word in a function definition. > > I wonder if anyone can suggest a trick to allow a redefinition like this. If > not, then roll on Widgets. > > Graham > > PS In case you want to know why I want to redefine this function, it’s for > the > following reason. Generally, mathematicians say that ln(0) is undefined, > whereas the limit as x approaches zero is minus infinity. This is a bit > subtle, > and LiveCode takes no real notice of this, so that in LC, ln(0) yields > “-inf”. > Despite a contrary definition in the LC dictionary, this text is then > regarded > as a number, which can cause confusion, at least to me. So my new ln(x) would > yield undefined for ln(0) and would use a symbol for minus infinity which LC > would not then recognise as a number. > _______________________________________________ _______________________________________________ use-livecode mailing list use-livecode@lists.runrev.com Please visit this url to subscribe, unsubscribe and manage your subscription preferences: http://lists.runrev.com/mailman/listinfo/use-livecode
