what's an lvalue? (was Re: Help with casts)

[Jonathan I. Kamens]

In article <1991Feb21.040145.8678 at cec1.wustl.edu>, abed at saturn.wustl.edu (Abed M. Hammoud) writes:
|> 	This is probably not a smart question...so please forgive me..
|> 	I am new to C, and I have been a couple of times encountering
|> 	the term lvalue...I looked it up in K&R C book but I still don't
|> 	get it...could some body please help me with a small description.

  From pages 64-65 of the March 1988 edition of the dragon book ("Compilers,
principles, techniques, and tools," by Alfred V. Aho, Ravi Sethi, and Jeffrey
D. Ullman):

L-values and R-values

There is a distinction between the meaning of identifiers on the left and
right sides of an assignment.  In each of the assignments

	i := 5;
	i := i + 1;

the right side specifies an integer value, while the left side specifies where
the value is to be stored.  Similarly, if p and q are pointers to characters,
and

	p^ :- q^;

the right side q^ specifies a character, while p^ specifies where the
character is to be stored.  The terms l-value and r-value refer to values that
are appropriate on the left and right side of an assignment, respectively. 
That is, r-values are what we usually think of as "values," while l-values are
locations.


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