ISO Pascal reference manual

6.3 Interfacing to Panos standard procedures
Using Pascal with other languages
To convert a procedure call specification given in abstract form (e.g. one
from the Panos Programmer's Reference Manual) into a form suitable for
use in a Pascal IMPORT statement, the following process should be
applied. (Note that standard procedures having procedure-type parameters
cannot be called from Pascal, and so should not be imported, and Pascal
procedures with procedure-type parameters similarly cannot be called from
a non-Pascal environment, and so should not be exported other than to
another Pascal module. This is because procedures in the calling standard
are passed purely by descriptor (they are not closures, i.e. there is no value
environment in which they expect to operate), whereas Pascal procedure
parameters are passed as full closures, and not in the standard manner.
1. Write down the abstract specification of the procedure.
2. If the type of any parameter or result includes the structure
RECORD( < format >), write a suitable record type specification in Pascal
for each such format. If the form 'RECORD( < format >) REF' occurs,
also define a type < rec_type > _ref as < rec_type > '. Rewrite the
specification using these new type names instead of the original forms, and
change the abstract syntax into the Pascal form, i.e. < param_name > :
< type >
3. If any parameters are of type STRING, then for each:
(a) decide on the maximum length of string which will be supplied to the
procedure from this module, for that parameter;
(b) define a type String < N > (if it does not already exist), where < N > is
the maximum length decided on in (a), and the type is defined as
PACKED ARRAY [1.. < N > OF Char;
(c) rewrite the parameter specification as two items: the first having the
original parameter name, but written in Pascal form, with its type
being String < N > ; the second having the parameter name with '_len'
appended, of type Integer, i.e. 'STRING: < par_name > ' is rewritten as
< par_name > : String < N >; < par_name > _len: Integer'.
4. If any parameters or results are of type HIDDEN, CARDINAL or
INTEGER, rewrite these parameter specifications as the parameter name
followed by the type Integer, e.g. 'HIDDEN: < par_name > ' becomes
< par_name > : Integer', and so on.
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