Re: [NTG-context] How to define such a function in lua? Sorry I don't have a name on it.

4 Dec 2008


      On Thu, Dec 4, 2008 at 5:28 PM, Hans Hagen  wrote:
...
Zhichu Chen wrote:
...
Hi,
I'm learning to use luatex these days, one day actually. It's very
interesting. Although reference manuals are available, I still don't
know how to implement my designation.
The thing is, I know there's a "self" variable for object-oriented
programming, like
==================================================================
\startluacode
testdata = { a = 0,
             b = 0,
             c = 0,
             plus = function (self)
                        self.c = self.a + self.b
                    end
           }
mytest = testdata
mytest.a=10
mytest.b=100
mytest:plus()
tex.print(mytest.c)
\stopluacode
==================================================================
OK, but what if I wanna do something more, like substract? I would
like to use another object, like
==================================================================
\startluacode
testdata = { a = 0,
             b = 0,
             c = 0,
             calc = Calc
           }
Calc     = { plus = function (self)
                        self.c = self.a + self.b
                    end,
             substract = function (self)
                        self.c = self.a - self.b
                    end
           }
mytest = testdata
mytest.a=10
mytest.b=100
mytest.calc:plus()
tex.print(mytest.c)
\stopluacode
==================================================================
Of course this won't work, for the "self" in Calc refers to mytest.calc
rather than mytest. How to implement things like that?
Calc     = { add = function (self)
                        self.c = self.a + self.b
                    end,
             substract = function (self)
                        self.c = self.a - self.b
                    end
           }
testdata = { a = 0,
             b = 0,
             c = 0,
             calc = function(self,f) return Calc[f](self) end
           }
mytest = testdata
mytest.a=10
mytest.b=100
Calc.add(testdata)
print(mytest.c)
testdata:calc("substract")
print(mytest.c)
Thanks
but it might make more sense to look into metatables (i assume that you
own the programming in lua book which explains that)
I don't have one :(, I'll take a good at it later.
Hans
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                                          Hans Hagen | PRAGMA ADE
              Ridderstraat 27 | 8061 GH Hasselt | The Netherlands
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                                             | www.pragma-pod.nl
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-- 
Best Regards
Chen
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          Zhi-chu Chen | Shanghai Synchrotron Radiation Facility
         No. 2019 | Jialuo Rd. | Jiading | Shanghai | P.R. China
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                                               | www.sinap.ac.cn
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