[chuck-users] passing by reference
Ge Wang
gewang at CS.Princeton.EDU
Sun Nov 27 20:13:46 EST 2005
Hi Eduard and all,
> I am trying to pass an integer by reference, but I can't get it right.
> Could any one help me on this? What I tried works fine for arrays, but
> not for integers only.
in chuck, references *cannot* be made to primitive types (int, float,
dur, time), only to objects. in function calling, primitives are always
passed by value, and non-primitives are always passed by reference (like
in Java), regardless of the usage of @. However, the compiler should
have caught the fact that a function has been declared to take an 'int @'
as argument - this is a bug, which has been fixed now and will be
included in 1.2.0.4. Additionally, arrays are always considered objects,
including arrays of primitives.
as for achieving pass-by-reference for primitive types, one way is to wrap
them in an object and pass the object:
//----------------------------------------
// slightly modified
// (@ have been removed from func args)
//-----------------------------------------
// define class to wrap int
class TheInt
{
int value;
}
// instantiate it
TheInt ti;
// set any initial values
5 => ti.value;
// call modify value
ModifyValue( ti, 10 );
// check again
<<< ti.value >>>;
fun void PrintArray( int array[] )
{
for( 0 => int i ; i < 10; i++ )
<<<"a[",i,"] = ", array[i]>>>;
}
fun int IsInArray(int array[], int num, int length )
{
if( length > array.cap() ) array.cap() => length;
if( !length ) return 0; // array is still empty
for( 0 => int i; i < length; i++ )
{
if( num == array[i] )
{
<<<num, " found in pos ", i >>>;
return 1; // num found in array
}
}
<<< num, " not found in array" >>>;
return 0; // not found
}
fun void ModifyValue( TheInt val, int newValue )
{
<<< "val is: " , val.value >>>;
newValue => val.value;
<<< "val is: " , val.value >>>;
}
fun void ModifyArray( int array[] )
{
for(0=>int i; i < array.cap(); i++)
array[i]*5 => array[i];
}
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