Re: LuaTeX 1.0.3 announcement

[Alan Braslau <alan.braslau@cea.fr>]

On Sat, 18 Feb 2017 14:59:14 +0100
luigi scarso <luigi.scarso@gmail.com> wrote:

> On Sat, Feb 18, 2017 at 2:27 PM, Henri Menke <henrimenke@gmail.com>
> wrote:
> > On 02/18/2017 09:42 AM, luigi scarso wrote:  
> >> On Sat, Feb 18, 2017 at 9:11 AM, Henri Menke
> >> <henrimenke@gmail.com> wrote:  
> >>> On 02/17/2017 08:57 PM, luigi scarso wrote:
> >>> How can I use the FFI?  There is nothing in the latest docs.
> >>> Thanks for all the efforts!  
> >> luatex ffi is beyond the "experimental state", and aims to  be
> >> compatible with luatexjit ffi.  
> >
> > So it has the same interface?  There seems to be no documentation
> > about it in the most recent manual from luatex.org  
> yes, "aims to be compatible" means same interface and functionality,
> but there is still lot of work to do,
> apart the dynamic  loading of the library and the C parser.
> But it's usable for testing.
> 

Luigi has shown me a simple and useful application of ffi:

\startluacode

ffi=require("ffi")
ffi.cdef[[
double j0(double x);
double j1(double x);
double jn(double x);
-- ...
]]

\stopluacode

These libm functions can then be used in lua as:

ffi.C.j0(x)

for example.

In my case, I pass them to MetaPost as:

\startMPdefinitions

vardef jzero primary x =
  scantokens(lua("mp.quoted(ffi.C.j0(" & decimal x & "))"))
enddef ;

\stopMPdefinitions

This experimental code appears to work quite well.

Thank you Luigi and Hans!

Alan
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