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4.4.2 Argument functions

Specific Scilab functions or C or Fortran routines can be used as an argument
of some high-level primitives (such as `ode`, `optim`, `dassl`...).
These fonctions are called argument functions or externals.
The calling sequence of this function or routine is imposed by
the high-level primitive which sets the argument of this function or
routine.
For example the function `costfunc` is an argument of
the `optim` primitive. Its calling sequence must be:
`[f,g,ind]=costfunc(x,ind)` as imposed by the `optim` primitive.
The following non-linear primitives in Scilab need argument functions
or subroutines:
`ode`, `optim`, `impl`, `dassl`, `intg`,
`odedc`, `fsolve`.
For problems where computation time is important, it is recommended
to use C or Fortran subroutines. Examples of such
subroutines are given in the directory `SCIDIR/routines/default`.
See the README file there for more details.

When such a subroutine is written it must be linked to Scilab.
This link operation can be done dynamically by the `link`
command. It is also possible to introduce the code in a more
permanent manner by inserting it in a specific interface in
`SCIDIR/routines/default` and rebuild a new Scilab by a
`make all` command in the Scilab directory.

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** Previous:** 4.4.1 Nonlinear Primitives
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