Depth-first search and replace? — John
On Sep 19, 2014, at 7:32 AM, David P. Sanders <[email protected]> wrote: > > > El viernes, 19 de septiembre de 2014 09:26:09 UTC-5, David P. Sanders > escribió: > > > El viernes, 19 de septiembre de 2014 08:58:56 UTC-5, Isaiah escribió: > To do what you want, very briefly: > > > x.args[3] == :pi && x.args[3] = Expr(:call, :BigFloat, :pi) > > This will make more sense if you look at `xdump` output to see how Exprs are > structured > (and `xdump` is quite handy to know about in general). Try: > > > > xdump(:(big(3) + big(pi))) > ... > > > Yes, that's what I need, thanks. Now I need to iterate over the (in principle > arbitrarily complex, i.e. nested) syntax tree and do this everywhere. > Is there a standard method for this kind of iteration? > > I guess some kind of recursion. I'll give it a go... > > > > > On Fri, Sep 19, 2014 at 9:42 AM, David P. Sanders <[email protected]> wrote: > > > El viernes, 19 de septiembre de 2014 08:34:05 UTC-5, David P. Sanders > escribió: > Hi, for a package I'm writing (or, more precisely, trying to write), I need > to do the following: > > Change `:(3 + pi)` > into `:(3 + big(pi))` > or `:(BigFloat(3) + BigFloat(pi))` > > I forgot to say that I need to do this so that I can perform the calculations > with different rounding modes. > > > Basically I need to apply `BigFloat` to every symbol in the expression. (I > believe that it would be sufficient to wrap `MathConst`s in `big`, but > converting everything to BigFloat is probably a good idea.) > > This is my first foray into parsing etc. I'm guessing there's a package that > allows me to do this easily -- could someone please point it out? > Or how should I go about this? > > In principle the expressions could be more complicated, e.g. `(3 + pi) * > (2.5 - e)` > > Thanks, > David. >
