Re: Reading Particular contents from file
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- Subject: Re: Reading Particular contents from file
- From: Tom N Harris <telliamed@...>
- Date: 2012年1月27日 01:56:46 -0500
On 01/25/2012 09:21 AM, Sandeep Ghai wrote:
Hello everyone,
I am doing file handling using Lua programming. But I need some help
where I got stuck.
I want to read particular line from the file.
consider the following file:-
...
I want to read 'x',and 'y' values whenever I pass argument to read
'nodes' and similarly for other contents(like constraint,forces etc) too.
After then I want to pass all these things directly into database,to
gather all the similar things from number of files.
Please help me in syntax. I am a beginner in Lua Programming.
Thank you in advance.
While the more professional thing to do would be to use LPEG, this is a
fast and only slightly error-prone way to get it done with string.match
and tail-calls as a state machine. Call parse_data_description with a
file handle and it will produce a table. Then move it into the database
with whatever backend you're using. I guessed at what fields may be
optional, so you'll want to tweak the 'material or "beam"' like expressions.
local headings
local function parse_problem_description(T, F)
local line = F:read()
if not line then
return T
end
if headings[line] then
return headings[line](T, F)
end
local title = string.match(line, '^title="([^"]*)"')
if title then
T.title = title
end
return parse_problem_description(T, F)
end
local function parse_nodes(T, F)
local line = F:read()
if not line then
return T
end
if headings[line] then
return headings[line](T, F)
end
local i,x,y = string.match(line, '^(%d+) +x=(%d+) +y=(%d+)')
if i then
i,x,y = tonumber(i),tonumber(x),tonumber(y)
local constraint = string.match(line, 'constraint=(%a+)')
local force = string.match(line, 'force=(%a+)')
T.nodes[i] = {
x = x,
y = y,
constraint = constraint or 'free',
force = force
}
end
return parse_nodes(T, F)
end
local function parse_beam_elements(T, F)
local line = F:read()
if not line then
return T
end
if headings[line] then
return headings[line](T, F)
end
local i,n1,n2 = string.match(line, '^(%d+) +nodes=%[(%d+),(%d+)%]')
if i then
i,n1,n2 = tonumber(i),tonumber(n1),tonumber(n2)
local material = string.match(line, 'material=(%a+)')
T.elements[i] = {
nodes = {n1,n2},
material = material or 'beam'
}
end
return parse_beam_elements(T, F)
end
headings = {
['problem description'] = parse_problem_description;
['nodes'] = parse_nodes;
['beam elements'] = parse_beam_elements;
}
function parse_data_description(F)
local T = { title="", nodes = {}, elements = {} }
return parse_problem_description(T, F)
end
--
- tom
telliamed@whoopdedo.org