Maple uses its own notation to describe external types.  This provides a generic well-defined interface for calling compiled code in any language.

The parameters arg1 through argN describe the arguments of the function to be called.  These should be specified in the order they appear in the documentation or source code for the external function.

The return value is also described by using a type descriptor, with the name RETURN as the argument identifier.

The data descriptors used to represent scalar formats usually contain a type name and size.  The size represents the number of bytes needed to represent the given hardware type.  The basic scalar types and their equivalents in C, Fortran, and Java are as follows.

The C type long is usually 4 bytes on 32-bit machines, and 8 bytes on 64-bit machines.

In addition to the basic types listed above, Maple also recognizes some compound types that can be derived from these basic types.  The following types are recognized by define_external.

Options to ARRAY are the same as those that can be passed to the Array constructor.  The only significant difference is that indexing functions must be specified with indfn=, and are not allowed unless using custom wrapper external calling.  The following options override any defaults normally assumed by the Array constructor.

Other compound types including structures, unions, and procedures can be recognized when generating wrapper libraries.

The following table describes the external types and the Maple types that can be automatically converted.  The first listed Maple type is the one to which a result of the corresponding external type is converted.

$\mathrm{last\_letter}≔\mathrm{define\_external}\left('\mathrm{last\_letter}'\,s::\mathrm{string}\,\mathrm{RETURN}::\mathrm{char}\,\mathrm{LIB}=''mylib.dll''\right)\:$

$\mathrm{last\_letter}\left(''whatever''\right)$

$''r''$

$\mathrm{times2}≔\mathrm{define\_external}\left('\mathrm{times2}'\,'x'::\mathrm{REF}\left(\mathrm{integer}\left[4\right]\right)\,\mathrm{LIB}=''libmy.so''\right)\:$

$n≔4\:$

$\mathrm{times2}\left('n'\right)\:$

$n$

$8$

$n≔5\:$

$\mathrm{times2}\left('n'\right)\:$

$n$

$5$

$\mathrm{sum\_elems}≔\mathrm{define\_external}\left('\mathrm{sum\_elems}'\,\mathrm{JAVA}\,\mathrm{CLASSPATH}=\mathrm{currentdir}\left(\right)\,\mathrm{RETURN}::\mathrm{float}\left[8\right]\,'a'::\mathrm{ARRAY}\left(\mathrm{float}\left[8\right]\right)\,'n'::\mathrm{integer}\left[4\right]\,\mathrm{LIB}=''jexttest''\right)\:$

$A≔\mathrm{Vector}\left(5\,i\mapsto i\,\mathrm{datatype}=\mathrm{float}\left[8\right]\right)\:$

$\mathrm{sum\_elems}\left(A\,5\right)$

$15$