Some notes about programming languages
Strong typing guarantees that there will not be any errors at runtime, and that type errors will be caught at compile time. With weak typing however, type failures are possible.
The static scope of a variable is defined by the most immediately enclosing block, and excludes all enclosed blocks redefining the variable.
Static scope can be determined at compile time, and is not modified by the order in which functions are executed at run time.
Stack: as function calls are made, their activation records are added to the stack, which includes allocated space for the variables declared in that function. That activation record is popped from the stack upon return.
Heap: memory allocated remains in existence for the duration of the program, unless explicitely deallocated. Caller function passes to the callee pointers to its stack values themselves pointing to the heap.
Advantages:
The dynamic scope of a variable is defined by all functions called after its decleration, until it is redeclared by a called function.
Dynamic scope cannot be determined at compile time, and is modified by the order in which functions are executed at run time.
Stack: as activation records are created, they contain pointers to the most recent declaration of the variable. All pointers from previous stack frames are forwarded to the new stack frame.
Advantages:
Examples: LISP, Perl
Shallow binding keeps a hash table with the latest binding, and stores old values on stack. Instead, deep binding keeps a stack of bindings. Note that, shallow binding brings a major improvement in speed.