HP SunSoft Pascal 4.0 Manuale Utente Scaricare il pdf (Pagina 117)

The C–Pascal Interface 93

Pascal Set Types

In Pascal, a set type is implemented as a bit vector, which is similar to a C

short-word array, where each short-word contains two bytes. Thus, sets are

bit-vectors, and they are allocated in multiples of 16 bits. To ﬁnd out the size

of a set, enter the following code:

Direct access to individual elements of a set is highly machine-dependent and

should be avoided.

General Parameter Passing in C and Pascal

A few general rules apply to parameter passing:

• C passes all arrays by reference since C strings are arrays.

• C passes all structures by value.

• In C, if you want to pass anything else by reference, then you must

explicitly prepend the reference ampersand (&), or pass an explicit pointer.

• Pascal passes all parameters by value unless you explicitly state that they

are var, in out, or out parameters, in which case they are passed by

reference.

Procedure Calls: C–Pascal

Here are examples of how a C main program calls a Pascal procedure:

ceiling( ord( highest_element ) / 16 )

The Pascal procedure, Samp, in

the ﬁle Samp.p. Note the

procedure deﬁnition.

procedure Samp(var i: integer; var r: real);

begin

i := 9;

r := 9.9

end; { Samp }

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HP SunSoft Pascal 4.0 Manuale Utente Pagina 117