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Topic: Static scoping


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In the News (Mon 15 Jul 19)

  
  Static Scoping - MIT/GNU Scheme 7.7.90+
Scheme is a statically scoped language with block structure.
The fact that Scheme is statically scoped (rather than dynamically bound) means that the environment that is extended (and becomes current) when a procedure is called is the environment in which the procedure was created (i.e.
Note that with static scoping, you can tell what binding a variable reference refers to just from looking at the text of the program; the referenced binding cannot depend on how the program is used.
www.gnu.org /software/mit-scheme/documentation/mit-scheme-ref/Static-Scoping.html   (378 words)

  
  Scope (programming) - Wikipedia, the free encyclopedia
A namespace is a scope that uses the enclosing nature of the scope to group logically related identifiers under a single identifier.
Static scope is standard in modern functional languages such as ML and Haskell because it allows the programmer to reason as if variable bindings are carried out by substitution.
Correct implementation of static scope in languages with first-class nested functions can be subtle, as it requires each function value to carry with it a record of the values of the variables that it depends on (the pair of the function and this environment is called a closure).
en.wikipedia.org /wiki/Static_scoping   (1279 words)

  
 [No title]
Static and dynamic scope ------------------------ The scope of a variable is the set of program statements in which the variable's binding is visible.
Problems with dynamic scoping: (i) local variables are always visible to called subprograms (unless local variables in the called subprograms have the same name) (ii) types of nonlocal variables cannot be statically checked because it is hard to find the applicable variable declaration.
Static scoping -- the set of statements in which variable bindings are visible can be determined by looking at the program text.
www.eecis.udel.edu /~chester/courses/670-04s/scope   (929 words)

  
 Chapter 09   (Site not responding. Last check: 2007-10-07)
Chain_offset - The length of the static chain needed to reach the correct activation record instance for a nonlocal reference to a variable X is exactly the difference between the static_depth of the procedure containing the reference to X and the static_depth of the procedure containing the declaration for X. This difference is the chain_offset.
One criticism of using the static chain to access nonlocal variables is that references to variables in scopes beyond the static parent are costly.
Because the static environment of an activation of a subprogram that has been passed as a parameter may have little relationship to the static environment of the subprogram in which it is called, in many cases several display pointers must be replaced.
csci.csusb.edu /public/csci/gvaldivi/education/cs320/lec/ch09.htm   (2354 words)

  
 Chapter 04   (Site not responding. Last check: 2007-10-07)
The scope and lifetime of the variable are clearly not the same because static scope is textual, or spatial, conception whereas lifetime is a temporal concept.
Dynamic scoping is a based on the calling sequence of subprograms, not on their spatial relationship to each other and can be determined only at run time.
The disadvantages of dynamic scoping is that during the time span beginning when a subprogram begins its execution and ending when that execution ends, the local variables of the subprogram are all visible to any other executing subprogram, regardless of its textual proximity.
csci.csusb.edu /public/csci/gvaldivi/education/cs320/lec/ch04.htm   (1744 words)

  
 3
Static variables in a C subroutine are live but not in scope when other subroutines are executing.
In C or C++ a global (static external) variable declared in one source file is live but not in scope when the execution is in another source file.
In dynamic scoping, the set_x and print_x in procedure second refer to the local x, and this does not affect the global x (referenced in the main program) after returning from second.
www.mines.edu /Academic/courses/math_cs/macs400/answers/assignment3.htm   (881 words)

  
 CSE 130 Lecture Notes
The scope of an identifier is the region of the program where applied occurrences refer back to this binding occurrence, i.e., the lexical range in which that identifier is visible.
Static scoping says that the "s" local to "update" is irrelevant to the function "scale", so the vector v will be magnified tenfold, not normalized.
Under static scoping, if all function values are created at compile-time, then identifiers can be discarded at run-time, because each use of a name can be compiled into a stack offset.
users.sdsc.edu /~ludaesch/CSE130/ln13.html   (2457 words)

  
 CS 2360 - February 24, 1998   (Site not responding. Last check: 2007-10-07)
Variables and scoping in LISP The variables created in the argument list of a function definition are, as you may know, local to the function, and they are bound to values when the function is called.
Under dynamic scoping, the variables in the argument list are bound when the function is called, and the values are accessible by this function and any function called by this function (and so on) until the evaluation of this function has ceased.
You can think of a dynamically scoped variable as being local to the function in which that variable is first bound, but global to all functions called by that first function (and all functions called by those functions, and so on...).
www.cc.gatech.edu /computing/classes/cs2360/winter98/lec15.html   (2674 words)

  
 Dynamic Scoping
When a variable reference is found by a statically scoped compiler, the characteristics of the variable are found where it is declared.
Under static scoping rules, the lexical level is used in most interpreters like a static chain pointer to control the search.
Depending on which type of scoping is preferred, the user must comment out one of the lines of code in the section labeled "Option 1: Static or Dynamic Scoping" in the instructor's version of the code.
math.holycross.edu /~mule/manual/chap4.htm   (2995 words)

  
 Operational Semantics of Block-Structured Languages: Variables
Static or lexical scoping means that the scope of a variable declaration is a particular region of program text.
Under static scoping, there is a unique declaration that applies to any particular use of a variable.
Second, static allocation means that it is not possible to have different outstanding activations of a procedure using different sets of local variables and parameters.
www.cs.sfu.ca /people/Faculty/Cameron/Teaching/383/varsem.html   (782 words)

  
 CHAPTER 4
Static variables are those that are bound to memory cells before program execution begins and remain bound to those same memory cells until program execution terminates.
Dynamic scoping is based on the calling sequence of subprograms, not on their spatial relationship to each other.
Also, dynamic scoping makes programs much more difficult to read, because the calling sequence of subprograms must be known to determine the meaning of references to non-local variables.
www.engin.umd.umich.edu /CIS/course.des/cis400/maxim/lectures/chp4.htm   (1445 words)

  
 355mt2study - WSUWiki
The scope of a declaration is all the locations in the program where the name(s) bound in that declaration are visible (that is, they can be referenced).
Under dynamic scoping, all three uses of x would yield 7 as the value and the overall result would be 21.
Under static scoping, x on line 2 is bound to 2, on line 4 is bound to 7 and on line 5 is bound to 7.
wiki.wsu.edu /wsuwiki/355mt2study   (958 words)

  
 Homework 7 - Sample Solution   (Site not responding. Last check: 2007-10-07)
The role of the static and dynamic links in the activation record is not clear.
The choice of whether a programming language uses static or dynamic scoping is determined by the creator of the language.
Static scoping is far more common (dynamic scoping it doesn't even exist in C, C++, or Java) because the resulting code is easier to understand.
carbon.cudenver.edu /~traup/fa05/lec/hw7-s.html   (1299 words)

  
 MuLE Static versus Dynamic Scoping Lab
The concept of dynamic verses static scoping is concerned which set of rules to apply when finding a binding to a variable and/or changing a value bound to a variable.
Whereas, static scoping rules depend only on the static structure of the program and therefore requires searching the executing subprogram’s static parent, i.e., the defining environment first.
The gain is every procedure’s static scope is identical, i.e., every procedure is defined in the global environment and thus, have the same static parent.
mathcs.holycross.edu /~mule/labs/SLamScoping.htm   (2472 words)

  
 Block-scope | Lambda the Ultimate
Without block scoping, the scope gets enriched after a loop which declares a variable, *if there was at least one iteration*.
still in my experience dynamic scoping does not make sense outside of the language extension domain, which is why i do suspect that pragmatism on the side of the implementation is the reason for such a choice in quite a few languages.
This becomes obvious when you comparing dynamic and static typing: the former starts out with basically complete flexibility while the latter is on the other end of the spectrum, but both can be moved towards each other.
lambda-the-ultimate.org /node/1775   (1509 words)

  
 [No title]
STATIC VERSUS DYNAMIC SCOPING In a nutshell, at "definition time", when an abstraction is evaluated to give a "function value": - under static scoping the function value is a closure which saves the current environment - under dynamic scoping, only the abstraction expression is saved.
Dynamic scoping violates alpha-conversion: if the parameter name x in the abstraction for times was changed to z, both static and dynamic scoping would give 20.
It is better to use static scoping and assignment.
www.cse.ucsd.edu /classes/wi98/cse230/Feb3   (684 words)

  
 CS245 Lab 4: Scoping Rules   (Site not responding. Last check: 2007-10-07)
Write a lisp function named test-scoping to investigate the scoping rules of lisp, with respect to local variables created by let (my experiments suggest that things are a bit different with respect to global variables).
Your function should return the string "dynamic" if the lisp system running the function uses dynamic scoping and "static" if it uses static scoping.
HINT - you may want to base your test-scoping function on an example from the book that produces different results based on the type of scoping used (it is appropriate to cite the source of your program in a comment if you do this).
www.haverford.edu /cmsc/course-pages/CMSC245/lab4.html   (342 words)

  
 lua-users wiki: Lua Scoping Discussion
I don't disagree that Lua is statically scoped.
This poor substitute for static nested scoping has been adopted because it makes it easy to produce an implementation in which all non-global variables are stack allocated, however, one need not give up static nested scoping to have stack allocated non-globals.
In a statically nested scoped language, the scope of an identifier is fixed at compile-time to be the smallest block (begin/end or function/procedure body) containing the identifier's declaration.
lua-users.org /wiki/LuaScopingDiscussion   (1587 words)

  
 [No title]   (Site not responding. Last check: 2007-10-07)
The key observation is that during compilation under static scoping, the compiler processes the program text from top down, so that the order in which it enters and leaves blocks is LIFO.
But the number of static links to follow to get from the top activation record on the stack (corresponding to h) to an activation record for f is given by the offset above.
So the answer to (2) is as follows: the destination of the new static link is obtained by starting with the current activation record (at the top of the stack), and following a number of activation records given by the offset computed for (1).
www.mathcs.sjsu.edu /faculty/smithj/oldclass/152s99/static.html   (426 words)

  
 static from FOLDOC
Static analysis techniques range from the most mundane (statistics on the density of comments, for instance) to the more complex, semantics-based techniques.
It is called "static" because it will retain a value as long as power is supplied, unlike dynamic random access memory (DRAM) which must be regularly refreshed.
Statically typed languages may have strong typing or weak typing.
foldoc.org /?static   (710 words)

  
 Pluvo Documentation: Features
scoping, "Static scoping also makes it much easier to make modular code and reason about it, since its binding structure can be understood in isolation.
In contrast, dynamic scope forces the programmer to anticipate all possible dynamic contexts in which the module's code may be invoked." Dynamic scoping is relatively rare in programming languages even though it's easier to implement—Pluvo was dynamically scoped in the very early stages of its implementation.
copied and called as a prototype, as a scope it will have three bound variables: name (passed on the constructor), homepage (passed on the constructor), and details (from the prototype), the latter of which is a method.
inamidst.com /pluvo/doc/features   (1152 words)

  
 CSE 130 Lecture Notes, April 29, 2002
Under static scoping, if all function values are created at compile-time, then identifiers can be discarded at run-time, because each use of an identifier can be compiled into a stack offset.
Names refer to values in the most recently entered scope, which can only be known at runtime.
A variable with this behaviour is called a static variable in C, or called an own variable in Algol 60.
www.cs.ucsd.edu /~elkan/130/april29.html   (542 words)

  
 CS4613 Assignment 7
Life time: if static, same as the program; if instant variables, same as the object; if local variables of a method, as long as a method call.
Since variable a may often change the types of values it holds, hence the memory locations where the values are store, a must be a reference variable and its dynamically assigned value must be in a dynamically allocated memory location, i.e.
The output is 1, since the local variable x of method fa() is closer to the method fb() on the system stack when the prinln() statement is executed at runtime.
www.cs.unb.ca /profs/wdu/cs4613/a7ans.htm   (677 words)

  
 CS334 Lecture 6
Scope of a variable is the range of program instructions over which the variable is known.
Scope is associated with the static text of program.
Therefore in Pascal (for example) there are three kinds of memory: static (occupied by global variables), stack-based or automatic (occupied by parameters and local variables of procedures and functions), and heap-based or manually allocated.
www.cs.williams.edu /~kim/cs334.97/Lec6.html   (1432 words)

  
 PHP: Variable scope - Manual
The scope of a variable is the context within which it is defined.
The variable is static with respect to the function and not the class.
But it seems that the static scope is not inherited: if class "a" inherit the "db access" class, then the "connection" variable is shared among "a" instances, not among both "a" AND "db access" instances.
www.php.net /static   (5003 words)

  
 Python Warts   (Site not responding. Last check: 2007-10-07)
This was done to avoid breaking existing code whose behaviour would have changed as a result of the new scoping rules; Python 2.1 printed warnings about programs that were going to produce different results in Python 2.2 so that everyone had lots of time to fix their code.
A more detailed explanation of the rules, and a dissection of the implementation, can be found in PEP 227: "Nested Scopes".
This problem went away because of the static scoping introduced in Python 2.1 and described in the previous section.
www.amk.ca /python/writing/warts.html   (3619 words)

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