Re: Why does lua interpreter need = in front of variables?
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- Subject: Re: Why does lua interpreter need = in front of variables?
- From: Niklas Frykholm <niklas@...>
- Date: 2007年10月16日 09:31:14 +0200
Matthew Wilson wrote:
I am learning lua after using python for the last few years.
In the lua toplevel, why do I either have to either put a "=" in front
of a variable
You might be interested in this. It is a little side project of mine
that makes lua work nicer in "calculator mode". It does away with the
need to type "=" in front of expressions, provides nicer output for
tables, enables you to "save" and "load" calculator sessions, and some
other stuff.
Just save the code in a lua file (e.g., calc.lua) and start it with "lua
calc.lua"...
---
function string:rep(n)
local out = ""
for i=1,n do out = out .. self end
return out
end
function string:left(n)
return self .. (" "):rep(n - self:len())
end
local function sort(t)
local sorted = {}
for k,v in pairs(t) do sorted[#sorted+1] = k end
table.sort(sorted)
local index = 0
return function ()
index = index + 1
local k = sorted[index]
return k, t[k]
end
end
local function line_representation(x,seen)
if type(x) == "table" then
if not seen then seen = {} end
if seen[x] then return "..." end
seen[x] = true
local r = "{"
for k,v in sort(x) do
r = r .. line_representation(k,seen) .. '=' ..
line_representation(v,seen) .. ', '
if r:len() > 40 then
r = r:sub(1,40)
r = r .. '...'
break
end
end
r = r .. '}'
return r
elseif type(x) == "string" then
x = string.gsub(x, '\n', '\\n')
x = string.gsub(x, '\r', '\\r')
x = string.gsub(x, '\t', '\\t')
if x:len() > 40 then
x = x:sub(1,40) .. '...'
end
return x
elseif type(x) == "function" then
local info = debug.getinfo(x)
if info.source:sub(1,1) == '@' then
local file = info.source:sub(2)
local f = io.open(file)
for i=1,info.linedefined-1 do f:read() end
local x = f:read() .. f:read() .. f:read()
return line_representation(x)
else
return line_representation(info.source)
end
else
return tostring(x)
end
end
local function ascii_table(t)
local out = ''
local klen = 20
local vlen = 20
for k,v in pairs(t) do
local kl = line_representation(k):len() + 2
local vl = line_representation(v):len() + 2
if kl > klen then klen = kl end
if vl > vlen then vlen = vl end
end
out = out .. ("-"):rep(klen+vlen+5) .. "\n"
for k,v in pairs(t) do
out = out .. "| " .. line_representation(k):left(klen) .. "| " ..
line_representation(v):left(vlen) .."|\n"
end
out = out .. ("-"):rep(klen+vlen+5) .. "\n"
return out
end
local function full_representation(x, seen)
if type(x) == "function" then
local info = debug.getinfo(x)
if info.source:sub(1,1) == '@' then
local file = info.source:sub(2)
local f = io.open(file)
for i=1,info.linedefined-1 do f:read() end
local nest = 0
local out = ""
while true do
local r = f:read()
if not r then return out end
out = out .. r .. "\n"
for w in r:gmatch("%a*") do
if w == "do" or w == "if" or w == "repeat" or w ==
"function" then
nest = nest + 1
elseif w == "end" then
nest = nest - 1
end
end
if nest == 0 then break end
end
return out
else
return info.source
end
elseif type(x) == "table" then
return ascii_table(x)
else
return tostring(x)
end
end
SESSION = {}
function save(file)
local f = io.open(file, 'w')
for _,line in ipairs(SESSION) do
f:write(line)
f:write("\n")
end
f:close()
error "Saved."
end
function load(file)
local f = io.open(file, 'r')
while true do
local line = f:read()
if not line then break end
loadstring(line)()
SESSION[#SESSION + 1] = line
end
f:close()
error "Loaded."
end
function world()
local prepend
while true do
local line
if prepend then
io.write ">> "
line = prepend .. '\n' .. io.read()
prepend = nil
else
io.write "$ "
line = io.read()
end
local src = "_ = " .. line
local assign = "_"
local f,e = loadstring(src)
if not f then
src = line
assign = nil
f,e = loadstring(src)
end
if f then
local ok,res = pcall(f)
if ok then
SESSION[#SESSION + 1] = src
end
if not ok then
print(res)
elseif assign then
print( full_representation(_G[assign]) )
end
elseif e:match("near '<eof>'") then
prepend = line
else
print(e)
end
end
end
world()