Memory allocation: Difference between revisions

=={{header|SNOBOL4}}==

In SNOBOL4, simple data values are just created and assigned to variables. Here, three separate strings are concatenated and stored as a newly allocated string variable:

<lang snobol4> newstring = "This is creating and saving" " a new single string " "starting with three separate strings."</lang>

Empty arrays are created by using the built-in function (the size is determined when it is created):

<lang snobol4> newarray = array(100)</lang>

Empty tables are similarly created using the built-in function (new entries can be simply added at any later time by just storing them into the table):

<lang snobol4> newtable = table()</lang>

User-defined datatypes (usually, multi-field structures) are defined using the data() built-in function (which creates the constructor and field access functions):

<lang snobol4> data("listnode(next,prev,datafield1,datafield2)")</lang>

Then you allocate a new example of the defined listnode data item by using the constructor the data() function created:

<lang snobol4> newnode = listnode(,,"string data value1",17)</lang>

The example thus created can be updated using the field access functions also created by the data() function:

<lang snobol4> datafield1(newnode) = "updated data value 1"</lang>

You don't need to explicitly de-allocate memory. When you leave a function which has declared local variables, data stored in those local variables is released upon return. You can also just store a null string into a variable, releasing the value that was stored in that variable previously:

<lang snobol4> newnode = </lang>

SNOBOL4 automatically garbage collects released data items on an as-needed basis, and moves allocated items to consolidate all released space (so memory fragmentation is never a problem). You can explicitly garbage collect if you really want to:

<lang snobol4> collect()