Re: convert numbers
----- Original Message -----
From: <irvm at ellijay.com>
To: "EUforum" <EUforum at topica.com>
Subject: Re: convert numbers
>
>
> On Sunday 12 October 2003 04:37 am, Louis wrote:
>
> > The value() function does not simply return a number. It returns two
> > things: a success/failure message and the number. Not as easy to use in a
> > calculation as above. Although value() is more rigorous than s2n(), I
> > suspect s2n() is much faster.
>
> Indeed, your function is 5 to 8 x faster than value().
> Which makes me think that I should take a look at some of my
> programs which use value() heavily - maybe I could speed them up
> significantly by writing my own conversion routines.
But be careful as that routine allows any string to be 'converted', even those
that are not 'numeric'.
Here is the Text-To-Number routine used by win32lib's getNumber() routine.
--/func W32_TextToNumber( sequence text )
--/ret Atom or Sequence: The number represented by the text, or
{Number,ErrorPosition}
--/desc This converts the text into a number.
-- If the text contains invalid characters, zero is returned. The text can
-- have leading and trailing whitespace characters.
--
-- /b "Note 1:" You can supply Hexadecimal values if the value is preceded by
-- a '#' character, Octal values if the value is preceded by a '@' character,
-- and Binary values if the value is preceded by a '!' character. With
-- hexadecimal values, the case of the digits 'A' - 'F' is not important. Also,
-- any period character embedded in the number is used with the correct base.
--
-- /b "Note 2:" Any underscore or comma characters, that are embedded in the
text
-- number are ignored. These can be used to help visual clarity for long
numbers.
--
--/b "Note 3:" You can supply a leading or trailing, minus or plus sign.
--
--/b "Note 4:" You can supply trailing percentage sign(s). Each one present
causes
-- the resulting value to be divided by 100.
--
-- This function can optionally return information about invalid numbers. If
-- /i text has the form of {sequence, integer} then if the integer is nonzero,
-- a sequence is returned. The first element is the value converted, and the
-- second is the position in the text where conversion stopped. If no errors
-- were found then this is zero.
--
--/code
-- sequence rc
-- atom val
-- rc = W32_TextToNumber({"12.34a", 1})
-- -- rc ---> {12.34, 6} -- Error at position 6
-- rc = W32_TextToNumber({"12.34", 1})
-- -- rc ---> {12.34, 0} -- No errors.
--
-- val = W32_TextToNumber("12.34a")
-- -- val ---> 0
--
-- val = W32_TextToNumber("#f80c") --> 63500
-- val = W32_TextToNumber("#f80c.7aa") --> 63500.47900390625
-- val = W32_TextToNumber("@1703") --> 963
-- val = W32_TextToNumber("!101101") --> 45
-- val = W32_TextToNumber("12_583_891") --> 12583891
-- val = W32_TextToNumber("12_583_891%") --> 125838.91
-- val = W32_TextToNumber("12,583,891%%") --> 1258.3891
--
--/endcode
constant vDigits = ".0123456789ABCDEF"
global function W32_TextToNumber( sequence text)
-- get the numeric value of text
integer dot,sign,tstart,tend, v, note, notify
atom lhs, rhs, lh, rh
integer base, pc
atom value
dot = 0
lh = 0
lhs = 0
rh = 0
rhs = 1
sign = 0
note = 0
base = 10
pc = 1
if length(text) = 2 and
sequence(text[1]) and
integer(text[2])
then
notify = text[2]
text = text[1]
else
notify = 0
end if
-- convert the value of the text
text = upper(text)
tstart = 1
tend = length(text)
-- Ignore leading whitespace
while tstart <= tend do
if equal(text[tstart], '-') and sign = 0 then
sign = -1
elsif equal (text[tstart],'+') and sign = 0 then
sign = 1
elsif equal (text[tstart],'#') then
base = 16
elsif equal (text[tstart],'@') then
base = 8
elsif equal (text[tstart],'!') then
base = 2
elsif find(text[tstart], {'\t', ' '}) = 0 then
exit
end if
tstart += 1
end while
-- Ignore trailing whitespace
while tstart <= tend do
if equal(text[tend], '-') and sign = 0 then
sign = -1
elsif equal(text[tend],'+') and sign = 0 then
sign = 1
elsif equal(text[tend],'%') then
pc *= 100
elsif find(text[tend], {'\t', ' '}) = 0 then
exit
end if
tend -= 1
end while
-- Set the default sign.
if sign = 0 then
sign = 1
end if
for i = tstart to tend do
if lhs > 0 and find(text[i],"_,") > 0 then
-- ignore an embedded grouping characters.
else
v = find(text[i], vDigits)
-- Invalid char so force a zero return.
if v = 1 then -- A dot found.
if dot = 0 then
dot = 1
else
note = i
if notify = 0 then
sign = 0
end if
exit
end if
else
v -= 1
if v < 0 or v > base then
-- Illegal char found.
note = i
if notify = 0 then
sign = 0
end if
exit
else
if dot = 1 then
rhs *= base
rh = (rh * base) + v - 1
else
lhs += 1
lh = (lh * base) + v - 1
end if
end if
end if
end if
-- I got to the end without error!
if i = tend then
note = 0
end if
end for
if rh = 0 and pc = 1 then
-- Common situation optimised for speed.
value = lh * sign
else
value = ((lh + (rh / rhs)) * sign) / pc
end if
if notify = 0 then
return value
else
return {value, note}
end if
end function
--
Derek
|
Not Categorized, Please Help
|
|
