A second take on this can exploit a simple
principle. While Mike's code loops over all
the possibilities to create a composite
"dictionary" string containing all the
characters, almost always you need to do
less than that. You just need to search until
what you find what you want, and then
stop.
For example,
local i = 1
while char(`++i') != "a" {
*
}
di `i'
or
local i = 1
while char(`i') != "a" {
local ++i
}
di `i'
This doesn't work so easily
with ` , and you wouldn't want
to do it repeatedly, so -- without
much checking -- here is another go.
------------------------- charfind.ado
*! NJC 1.0.0 11 June 2006
program charfind
version 8.2
if `"`0''"' == `"`=char(96)''"' {
di as res "96"
exit 0
}
else {
local i = 1
while char(`i') != `"`0'"' {
local ++i
if `i' == 256 Goerror
}
di as res "`i'"
}
end
program Goerror
di as err "invalid character"
exit 498
end
-----------------------------
Nick
[email protected]
> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Nick Cox
> Sent: 10 June 2006 20:16
> To: [email protected]
> Subject: st: RE: Trying to do inverse of char(n) without Mata ascii()
>
>
> A problem with this is likely to be that the tab
> character maps to multiple spaces, so messing up
> your counting.
>
> But in terms of your immediate question, look
> again at
>
> strpos(`"`charorder'""', "a")
>
> The first five quotes read off (d = double, s = single, q = quote)
> `" left compound d.q.
> ` left s.q.
> ' right s.q.
> " d.q.
> "' right compound d.q.
> and are thus, as Stata says, not balanced.
>
> Nick
> [email protected]
>
> Mike Lacy
>
> > I was trying implement a code fragment to give the number
> of a given
> > character, i.e., the inverse of char(n) without using the
> Mata ascii
> > function. (One of my reasons for doing it is that I am
> annoyed by the
> > idea that this is not simply an ordinary function in Stata.) So, I
> > tried the following:
> >
> > *Construct a list of all the characters in order
> > local charorder = ""
> > forval i = 1/255 {
> > local c = char(`i')
> > if `i' ~= 96 { /* avoid the pesky open-quote */
> > local charorder = `"`charorder'`c'"'
> > }
> > else { /* stick in a stand in */
> > local charorder = `"`charorder'zzz"'
> > }
> > }
> > local charorder = subinstr(`"`charorder'"', "zzz", "`",1)
> > *
> > di " The whole list: " `"`charorder""'
> > * try finding something
> > di "Letter a is found at ", strpos(`"`charorder'""', "a")
> >
> > While there may well be a more elegant way to get the open-quote
> > character into a macro that also contains " and ', what I am most
> > stuck with is the very last line, in which I tried to use strpos to
> > find the position of a
> > sample character, and the response is "too few quote," which
> > presumably is the interpreter's complaint about
> > `"`charorder'""' in strpos().
> > Any suggestions here?
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
