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-- shows how to trace assigments to global variables
-- a tostring that quotes strings. note the use of the original tostring.
local tostring=function(a)
if tag(a)==tag("") then
return format("%q",a)
else
return %tostring(a)
end
end
local T=newtag()
local Tlog=function (name,old,new)
local t=getinfo(3,"Sl")
local line=t.currentline
write(t.source)
if line>=0 then write(":",line) end
write(" -- ",name," is now ",%tostring(new)," (was ",%tostring(old),")","\n")
end
local Tgetnew=function (name)
local t=settag({},%T)
rawset(globals(),name,t)
return nil
end
local Tsetnew=function (name,old,new)
%Tlog(name,old,new)
local t=settag({value=new},%T)
rawset(globals(),name,t)
return t
end
local Tsetglobal=function (name,old,new)
%Tlog(name,old.value,new)
old.value=new
end
local Tgetglobal=function (x,value)
return value.value
end
settagmethod(T,"getglobal",Tgetglobal)
settagmethod(T,"setglobal",Tsetglobal)
-- to trace only selected variables, use the following function
-- and comment the next two calls to settagmethod
function trace(name)
local t=settag({value=rawget(globals(),name)},%T)
rawset(globals(),name,t)
end
settagmethod(tag(nil),"getglobal",Tgetnew)
settagmethod(tag(nil),"setglobal",Tsetnew)
-- an example
trace"a"
print(a)
a=1
b=2
c=3
a=10
b=20
c=30
trace"b"
b="lua"
c={}
a=print
c=nil
c=100
print(a,b,c,d)
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