RE: lex parsing floating point values

[Mike Spencer <mike@...>]

hey that's really great, thankyou Peter.

i got a lot of replies back saying make the data file a Lua script, which i
would do if the data file was solely for my own purposes.

but for the time being a general purpose parser is much more useful to me as
it can parse any kind of ascii file with floating point values in it. e.g.
exported data from 3d packages.

the 'autotable' and 'metatable' stuff looks good, so i'll be taking at look
at that also.

thanks all.

-----Original Message-----
From: Peter Shook [mailto:pshook@hotmail.com]
Sent: 28 May 2003 20:54
To: lua@bazar2.conectiva.com.br
Subject: Re: lex parsing floating point values


Mike Spencer wrote:
>
>but i would also like to know how to parse floating point using lex

Try this:

$ cat test
1
1.0
.01
x -1 junk
-.01
-1.68587e-007
Particles = 100
Emitter.delay = 0.001
Emitter.delayFuzz = 0

$ lua lex_number.lua test
1
number='1' start=1 end=2

1.0
number='1.0' start=1 end=4

.01
number='.01' start=1 end=4

x -1 junk
number='-1' start=3 end=5

-.01
number='-.01' start=1 end=5

-1.68587e-007
number='-1.68587e-007' start=1 end=14

Particles = 100
number='100' start=13 end=16

Emitter.delay = 0.001
number='0.001' start=17 end=22

Emitter.delayFuzz = 0
number='0' start=21 end=22


$ cat lex_number.lua

function number(str)
  local s = string.find(str, '%-?%.?%d')
  if s then
    local b,e1,e2,e3,e4
    b,e1 = string.find(str, '^%-?%d+%.%d*', s)  -- D+ . D*
    b,e2 = string.find(str, '^%-?%d*%.%d+', s)  -- D* . D+
    b,e3 = string.find(str, '^%-?%d+', s)       -- D+
    local c = e1 or e2 or e3
    b,e4 = string.find(str, '^[Ee][+-]?%d+', c+1)
    local e = e4 or c
    return string.sub(str, s, e), s, e+1
  end
end

function printf(...) io.write(string.format(unpack(arg))) end

local filename = arg[1]

for l in io.lines(filename) do
  print(l)
  local n, s, e = number(l)
  if n then
    printf("number='%s' start=%d end=%d\n\n", n, s, e)
  end
end

- Peter Shook

_________________________________________________________________
Add photos to your e-mail with MSN 8. Get 2 months FREE*.  
http://join.msn.com/?page=features/featuredemail