Static Scoping vs Dynamic Scoping November 26, 2013

Many C programmers might not have heard the term ‘Static Scoping’ and ‘Dynamic Scoping’. Since C only supports Static Scoping. Static Scoping is also called Lexical/Text Scoping.

Read the following article to understand what these two scoping mean in Computer Science.

1.  Article 1

2. Article 2

3. Article 3

The above things might confuse since this dynamic scoping is not supported in many languages including C and hence you might not be able to test the same. But the point is to understand it. What Dynamic Scoping means.

 

 

 

 

Got amazed by the exppression &(((struct st *) 0) ->member_st). But finally found this is valid and C has similar implementation for ‘offsetof’ September 16, 2013

Some day back i was going through some library code in C and found expression like

 &(((some_struct_type *) 0) -> some_element_of_some_struct_type);

And started wondering what will happen to access an element located at NULL. Thought something is wrong with the code then one of my senior suggested suggested this is Ok and then found lot of information on the web. Also the same feature is available in C as MACRO offsetof.

1. Stackoverflow

2. Stackoverflow

3. C wiki

4. C examples

 

Conclusion:

* The expression ((some_struct_type *) 0) -> some_element_of_some_struct_type is invalid/undefined because we are trying to access element of some structure which is not correctly located at defined address. But the expression prefix with & becomes valid because the whole expression of getting address of member element of struct (assumed to be located at NULL) is calculated at compile time and hence dereferencing is avoided.

 

nfa to dfa conversion best explained July 26, 2010

Here is the example from ullman sethi

link

other links of programs

Finding First{},and Follow{} -Compiler February 12, 2010