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tupleSet

Set the value of an element of a tuple from its position.
If the position is out of range, the function will return nil.

This function should be reserved to the advanced developers only, a bad use can do something unwanted. A good use should be safe.

Usually, two cases can occur :

• You can set with any type, even if it is different than the old type. Depending on what you wish to do, this may don't be a problem. But remember you that for all futures treatments the type has changed. This may be harmless ... or not.

  Look this code, it works fine :

  typeof TUPLE = [I I I];;
  
  fun displayTuple (a, n)=
  	if n < 0 then
  		0
  	else
  	(
  		_fooId tupleGet a n nil;
  		displayTuple a n-1
  	);;
  	
  fun main ()=
  	_showconsole;
  	set TUPLE = [1 5 4];
  	_fooS "TUPLE";
  	_fooId tupleGet TUPLE 1 nil;
  	displayTuple TUPLE (tupleSize TUPLE)-1;
  	tupleSet TUPLE 1 "string";
  	_fooS tupleGet TUPLE 1 nil;
  	displayTuple TUPLE (tupleSize TUPLE)-1;
  	0;;

  The type displayTuple is fun [u0 I] I and _fooId accepts all types. However, in some complex process, a modified type can be dangerous.
  Finally, even if the type of TUPLE is [I I I], Scol " accepts " this change to [I S I] during the execution (because the prototype of the tuple in tupleGet is u0 during the compilation and Scol ignores types to the execution).

  Other example :

  fun main ()=
  	_showconsole;
  	let 0 -> a in
  	let tupleSet a 0 "string" -> b in
  	(
  	_fooId a;	// 0
  	_fooId b;	// 0
  	_fooS tupleGet b 0 nil;	// string
  	);

  tupleSet returns an integer because 'a' is an integer (even if it is not a tuple ! tupleSet returns the same type), therefore b is an integer : _fooId b is correct.
  tupleGet b 0 nil returns the first and unique element of b, a string. It is correct with _fooS.

  Now, a "little" change :
  

  fun main ()=
  	_showconsole;
  	let 0 -> a in
  	let tupleSet a 0 "string" -> b in
  	(
  	_fooId a;
  	_fooS b;	// change _fooId by _fooS
  	_fooS tupleGet b 0 nil;
  	);

  Here, this code crashes :

  >>> ERROR - Type mismatch (detail):
Found: [I S S]
Expected: [I I u0]
<<<

  Indeed, b (see above) is considered by Scol like an integer, not like a string.

  Developers to be careful what they do !

• If you change the old value by a new value of the same type, you should have no problem.

Prototype :

fun [u0 I u1] u0

• u0 : a tuple. If this argument is not a tuple, the application can have an undefined behavior (see 2nd and 3rd examples above).
• I : a position. If the position is out of range, nil will be returned
• u1 : a new value

Return : u0 the same tuple or nil if error

See also :

tupleGet

tupleSize

Example :

fun setTuple (tuple, c)=
	set tuple = tupleSet tuple 0 c;		// set the first element to 'c'
	if c < tupleGet tuple 1 nil then	// set the second element if the condition is true
		set tuple = tupleSet tuple 1 c + tupleGet tuple 1 nil;	// old value + 'c'
	else
		nil;
	0;;

fun initTuple (tuple, a, b)=
	set tuple = [a b b];
	// others things to do
	0;;

Note

The first element has always the index 0.