Passing Parameters by Reference (2015-07-14 02:36 by toml_12953 #76538)
BASIC has an option switch to choose between passing paramters by reference or passing them by value (ISO standard). Does this apply to FUNCTIONs as well as SUBs? If so how do I specify in my program that the parameters are to be passed by reference? I'd really like to be able to modify arrays passed to a function and have the changes visible even after the function has ended. The option doesn't seem to affect the way parameters are passed at all. I see no difference whichever way I set the option.
Re: Passing Parameters by Reference (2015-07-14 21:20 by Kazuo SHIRAISHI #76544)
[Reply To Message #76538]
Subs can be passed the parameters by values in such a manner
10 SUB s(x)
20 LET x=2
30 END SUB
40 LET n=1
50 CALL s((n))
60 PRINT n
70 END
But FUNCTIONs do not have such an expedient.
DEFs have an option whether parameters shall be passed by reference on Decimal BASIC, but this not legitimate in Full BASIC.
Re: Passing Parameters by Reference (2015-07-14 22:41 by toml_12953 #76545)
[Reply To Message #76544]
> [Reply To Message #76538]
> Subs can be passed the parameters by values in such a manner
> 10 SUB s(x)
> 20 LET x=2
> 30 END SUB
> 40 LET n=1
> 50 CALL s((n))
> 60 PRINT n
> 70 END
> But FUNCTIONs do not have such an expedient.
> DEFs have an option whether parameters shall be passed by reference on Decimal BASIC, but this not legitimate in Full BASIC.
>
I do know about SUBs but the parameter passing option isn't necessary for those. I need the option in the menu to change the way parameters are passed to FUNCTIONs:
DECLARE EXTERNAL FUNCTION f
DIM a(10)
LET a(5)=3
LET b=f(a)
PRINT a(5)
END
EXTERNAL FUNCTION f(x())
LET x(5)=-1
LET f = 0
END FUNCTION
If parameters are passed by reference, this should print -1. It prints 3 no matter which way I set the parameter option.
Re: Passing Parameters by Reference (2015-07-19 11:41 by SHIRAISHI Kazuo #76561)
Full BASIC standard denies functions to have an argument that refers a variabale.
Decimal BASIC's option on DEF statements does not afect FUNCTION ～ END FNCTION, because it is difficult to write a function in a DEF statement which changes the value of the parameter variable, that is, allowing parameters passed by refference in a function defined in a DEF statement seldom harm the Full BASIC standard.
toml_12953 #76538)
