Re: Passing Parameter as Variable vs as address of variable

Hi Patrik

Just a touch more.

When a parameter is passed from RPG, it will be passed by reference by default. In this case, there is no copying of the variable contents to another address, so no time taken to duplicate anything.

If, as Barbara mentioned, specify CONST on the parameter of the prototype, then a copy of the variable is made at a new address, and that address is passed.

Also, I did mean to say that a pointer is only a "look at what is at this address" - if you pass a pointer by value, there is no data type information included - so if you are passing a pointer to an integer, there is no check that, in fact, it is an integer. That is the danger of passing a pointer by value.

In another exchange here, you asked, why was BY VALUE added? The reason is, certain system APIs and Unix-style functions require it. An example is the access() function, which tells you whether a file can be accessed in a certain manner - many of us use it to see if an IFS object exists.

This is the C/C++ declaration -

       int access(const char/*path/, int/amode/);

You have to pass the 2nd parameter by value - and use the VALUE keyword in the prototype in RPG.

Regards
Vern