adda markup's conflicts with ini format

10.25: news.adda/markup/conflicts with ini format:
. bzr (the ubuntu team's distrib'd cvs)
uses an ini folder with the catgories of
[/] and [groups] .
. generally the ini format can
conflict with the adda markup lang's syntax
because it uses brackets as category headers,
and the category name may consist of a single symbol character .

double-equal to mean prolonged equality

10.12: adda/lexicon/==:
. the == could be like the japanese way of
2-trees representing many trees: a forest .
. 2 equals would say the values are
equal for many moments,
ie, they are pointers to the same obj; [10.13:
or they are part of a notify&update pattern .
it could also be used as a special form of
assignment stmt:
whatever you're getting access to,
you have some way of maintaining synchronization,
as would occur if using aliases .]

meta.compiler

10.10: adda/meta.compiler:
. there should be a meta.compiler
that lets you  write a list of
transforms from adda to target lang
and then the meta compiler is
generating the compiler from this list .
. to get started, just make the usual compiler;
and, along the way,
be looking for how to generalize the process;
--
. the first step is to finalize the adda lang,
then write a translation map from general adda
to the simple adda that maps directly to c
(eg, procedures can't be nested ).

types of access constraints

10.5: todo.adda/types of access constraints:
. {rom, wom, xom, xwm} could be the keywords for the
various types of access constraint for
read-, write-, execute-, and write&execute- only-memory .
. instead of having any combo of rwx,
consider that an execute priv'
implies a read priv' .
. the original unix way had in mind
-- in addition to the self, group, world groups --
a sort of 4th group: executives
those whose activities depended upon
what file they opened .
other ideas:
. when does the system need an exe'able permission?
. if that app is an executive,
then it can execute any type it recognizes as exe'able .
todo:
. review previous ideas of
how an obj's name can include access types;
(just as it includes its datatype);
eg, f.txt mean obj"f is type"txt,
so then how does its name explain
access constraints such as (rom vs rwm)
and (in vs out) param types ?

10.21: adda/types of access constraints/intro:
. the fundamental operation of unix
revolves around this:
a user with privilege status of
{owner, member of owner's group}
is applying an app to a file,
if the app and file permissions permit it .
. a file may be located in
either a private or public space:
a private space is usable by
whoever has the owner's key .
. the key holder claims self belongs to a group;
and other users can belong to the same group .
. files can grant separate permissions for
{ owner (what the keyholder can do)
, in-group (what the owner's group can do)
, in-others (what anyone can do)
}.
. an executive is a special type of app
that uses its input data
as the source of instructions it will follow
including the decision of
what it will affect on the computer;
whereas non-exec's will decide their behavior
only from their constant program code,
along with their memory of their previous behavior,
and changes in the machine's state .
. most of these non-exec's are just editors,
affecting at most the files they are given,
some private mem, and the screen buffer .
. files should be tagged executable {xom, xwm}
only if their data is suitable for
instructing some executive .

. a user can be thought of as being
a sort of executive app .
. the user's actual executive power
is determined by which group of app's
the user is allowed to execute
which in turn is determined by
the executive apps' file permissions
and whether the file considers the user
to be {owner, in-group, others}.

. executives can be calling other executives,
just as the user calls them,
so, suppose a called executive
is considered to have the same priviledge
as the {executive, user} that called it;
then, a human user could run a public app,
and when that app tries to access
the user's private files,
this would be allowed .

. the exe'able permission is saying
that if you are an executive
you can read this even if
your caller doesn't have read permission;
likewise,
having a read permission is saying:
you can read this regardless of
whether you're an executive or not .

. so, all of that was the typical
unix permissions scheme;
an alternative is capability based security:

. an app can only access
the files that are within the folders that are
listed in the app's capability descriptor .
. file's and folders, too,
can have a capability descriptor
that can override any app's capabilities .

window config' generation and automation

9.27: adde/gui/window config' generation and automation:
. once windows are arranged in an oft-used way,
you can generate an icon representing that way,
and have it become available by menu .
. to customize your menu item,
there's a pallet of icon styles:
# a miniature of the current display,
# an abstract view with only window frames,
# and either of the above with
names of chosen apps added to the icon .
. for speedy creation of window arrangements,
there is a window drawing mode,
such that anything you do with mouse
affects only the frames of the windows,
not their content;
so, you don't need to be a sharp shooter
targeting scrollbars or tiny buttons .
. also, the windows are auto'ly tiled,
so your point selections don't have to be exact .
. a mouse-down dragged to another point
makes a rectangle, as usual;
then clicking in the resulting rectangle
brings up a list of frequently used app's and folders;
the default is a finder window .
-- todo:
that reminds how ipad
lets you scroll with multi-touch
maybe they have something for auto-tiling too?
. I remember the mac plus in 1985,
it had an easy drawing app that so inspired me .

function graph editing

8.4: adde/function graph editing:

. how is audio graphing done?
how is the gui separated from the command processor?

. each unit of mouse movement
practically represents a pixel unit
which then represents a range of data points;
the first of those points can be chosen;
or if there is a sharp spike
then find the high and low
to include every point inclusive;
ie, graph a vertical line instead of a point .

. audio graphing is like strings of words,
but instead of the words differing in length,
they are all on their side for differing height .
. range selections result in a pair of numbers:
the {begin, end} of range,
which are then sent to the processor .
. if the range was possibly modified,
the editor then has to regraph that range .
8.28:
. the editor can handle this without knowing
the particulars of the audio graphing,
because it will have an interface for
generic function editing;
or rather,
the editor and every command processor
will all speak the system language:
the system's language describes
a mathematical function
as either a set of points or a formula
along with a type specification that includes
a domain and codomain;
with an optional subdomain and inverse operator .

when software capitalists become dictators

7.4: adds/security
/when software capitalists become dictators:
. we see what a mess engineers have made of
the internet and computer security;
as chips make more decisions in our appliances,
they are like new laws imposed upon our nature;
this is where capitalists would be legislators;
and they must therefore submit to our constitution:
ie, representatives are elected,
initiatives can be brought by the people
and laws are open to public scrutiny .
. not only is opensource software not communism
(Bill Gates was misquoted as suggesting this);
but software as private capital
is sure to present an inevitable tyranny
just like a communism will
without the checks and balances of
democracy and separation of powers .

7.15: adds/robot/constitution with context casing:
. one way to balance private and public interests
is by including a context chip,
which has the ability to override other chips
whenever it senses the robot is on public property .
. it would also have final say over
the use of force the public is interested in .

TDD (Test-Driven Development)

web.adds/sw.dev.process 
/TDD (Test-Driven Development):
7.1:
"( my python web app is obs ! )
"( you forgot your TDD unit tests, pal )
. what is TDD?  Test-Driven Development
TDD != Unit Testing Dave Rolsky 2009
7.5: synth:
. in test driven development,
rather than ask "(how to impl this feature?),
we ask "(how do you prove
that a feature is impl'd?)
-- and that drives your interface design
(ie, the tests are designed even before
the interfaces, not just the bodies).
links:
sw.dev.process @ wiki
Xunit options for obj'c

agilepainrelief.com:

 I’ve been on projects where we tried to write
all of our tests after the classes were written.
Our test suite was valuable
 and prevented many regressions.
But it allowed many issues to slip through.
Weaker elements in API’s were often missed
and were changed only at a later date
at some expense.
Tightly coupled code was allowed to evolve
making some elements of the application
very difficult to test
without having to create dozens of
other (often unnecessary) objects.
As a result of all this
it became more difficult to write test cases over time.
Would TDD have solved all of these problems?
Perhaps not but it would have forced us to
confront many of them sooner.  

unit testing vs Test-driven_development
. the unit test tries to verify
all features of a given module;
 tdd (Test-driven development) is about
using tests as documentation:
. assuming you already have
libraries of utilities and datatypes,
you design the interface first
then the tests, and finally the bodies
that will make the tests pass .
. if you are writing your documentation first;
then you won't have any problems with also
writing test harnesses before the app is built .

. this is supposed to complement prototyping:
the developer often needs a semi-working model
to get ideas for a more polished model .
. the prototype is then used as the basis
for a high-reliability app
that writes the final design as a set of
user doc's, unit tests,
maint'doc's, feature tests,
and functional tests (having each function
beginning with precondition testing
and ending with postcondition testing).

. reverting to the last version that passed all tests
may often be more productive than debugging.

instead of relying on platform services directly,
they should be accessed through a wrapper,
so that functional testing can be applied .
--
See dependency inversion principle

including obj'c features

7.23: adda/oop/including obj'c features:

. in the expression"( a`b(x)`c ),
the ( a`b(x) ) means
the object"a has a procedure b(x)
that returns an object location
whose available functions include c .
. the syntax"(a`b) is not necessarily
involving self-modification;
it simply means subprogram"b has access to (a)
as an inout parameter
(the subprogram's object parameter).

. is there some efficient way of doing a`b`c
without passing pointers ?
I was thinking there was some virtual way
that doesn't really need pointers
(oop doesn't really need
all the pointers it thinks it needs)...

. if a subprogram's object param
returns a reference to something other than
the object param,
then in the c translation of same
this subprogram takes a destination param;
ie, a param that inputs a destination address
showing where the caller wants the return placed .

. why wouldn't it always take a destination param
even when returning self? ...
because the caller is already housing that obj .

7.26:
. my original concern here
was allowing the passing of references
and the use of object param's,
just like obj'c oop does,
while still using the sort of oop system
that did not generate garbage .
todo:
. I think obj'c has the convention that
even if ( a`b(x) doesn't return anything
if an object reference is expected as a return,
as is the case in "( a`b(x)`c ),
then it will use a reference to (a);
ie, ( a`b(x)`c ) would equal:
( a`b(x); a`c ) .

protecting the stack limits

7.22: adda/protecting the stack limits:

. how can one test for stack limits per platform?
if you test it once per platform
could the limit become smaller later?
it could depend on number of processes,
and current ram count ?
the user or an error could downgrade ram .
some help from addm:
. one thing that helps the stack problem
is assuming that user programs are addm code
rather than native code;
addm uses the c stack in a very limited way
and puts the user's stack entirely in the heap;
the user does call standard libraries
that in turn are native code;
but these can be designed to conserve stack space
(eg,
all recursive routines are finding some way to
serialize the large jobs;
eg, instead of giving gig's to quicksort,
the sorter breaks the job into mbyte sections,
and gives the quicksort's sections to mergesort ).
...
but can't the user can program natively? yes:
(see adda/natively coded extensions)
the user isn't restricted to addm,
so adda must be aware of some stack limits
and provide protections against overflow .

symbol table linking

7.14: 7.15: adda/symbol table linking:

. etrees (expression trees)
are tree nodes with pointers into
global and local dictionaries of symbols
(symbol tables).
. every etree module
implies access to a global symbol table,
and must specify any needed local symbol tables .
. there can be more than one local symbol table;
because, a dictionary can include procedures;
and, procedure definitions can have
local dictionaries:
the parent procedure becomes the
scope of its local dictionary,
hence the term "(nested scopes),
involving stacks of local symbol tables .
. each module has a tree of symbol tables .
. a typical scope path is:
module/subprog/nested sub/nested block/nested block .

. the 3 main uses of "(library) include
system, standard, and custom .
. the system library of an addx installation
is a service for organizing and linking
the modules that are available for reuse .
. a standard library is a module that is
declared by the system's language .
. a custom library is one added by the user .
. each module has a list of imported modules,
and a tree of symbol tables
to match its tree of nested scopes .

. when designing the pointer that is
going from etree nodes into symbol tables,
there must be an efficient coding,
and it should support efficient copying
even when it involves context changes
(re: adde/object copy & paste).

etree node variants for library symbols:
. there is first a bit to distinguish
symbol location type in {library, local}:
# library location:
. there may be many libraries in use (15-bit),
and many symbols per library (16-bit) .
# local location:
. there's often no more than
4 nested levels of locals (2bit);
and often less than 256 symbols per local (8bit).
but if node`size is in increments of 16bit chunks
that division could be 4 bits for 16 nested scopes,
and an 11-bit space for locals,
or less if the descriminant is more than 1 bit .
[7.30:
... in any case, the more space you save,
the less efficient it is to remap etree nodes
to a new symbol table after a context change .]

details of library location:
. there could be an infinity of libraries over time,
so the library codes in an etree node
don't represent specific libraries,
rather they represent a slot in the module's
list of imported or required libraries;
however, standard libraries can be specified,
since there are a finite number of them;
ie, if the code is in the range that is
reserved for standard lib's,
then that is the same code used by
the system library;
otherwise, we need to use the module's import list
to convert the symbol table's code
into one that the system library recognizes .

. the system library creates a custom lib's code
by taking a Secure Hash of its interface
. as long as that didn't change,
it would be considered the same library . 

natively coded extensions

7.22: adda/natively coded extensions:
. the adda compiler helps turn adda code
into obj'c code,
and then the user plugs that into xcode
to generate mac programs .
. there are 2 styles of user programming:
# extending addm:
. the user want's their library unit to be
seen by addm,
so that user's library unit is callable from
user's other scripts .
. this entails compiling the library unit,
recompiling addm to bind with the library unit
and relinking addm with the entire library .
. this is known as pythonic development:
a module is run as translated vm code
until it's perfected:
then it's promoted to native code
and made available in the account's library .
# building native apps:
. in building a native app,
adda code is translated to the native lang
(eg, mac speaks obj'c & cocoa).
. the native program then imports
the relevant adda libraries
and includes addm as a component
so that the program or its user
can run arbitrary adda scripts .

object copy & paste

7.14: adde/object copy & paste:

. the typical copy & paste
is a char-string operation;
whereas, an object selection
is operating over etrees (expression trees)
which are tree nodes with pointers into
dictionaries of symbols (symbol tables).
. there can be more than one symbol table;
because, a dictionary can include procedures,
and procedure definitions can have local dictionaries;
hence, a single etree can be within
the scope of multiple dictionaries
represented by stacks of local symbol tables .

. a copy becomes a module
meaning it needs its own copy of
any local symbol tables;
however, the cost of copying
depends on the destination:
if the paste location is within the source's scope
it shares all the same symbol tables .
. when some symbol tables are
not shared between source and destination
those tables must be copied;
and, affected etree nodes adjusted
to point into the new tables .

. when an arbitrary substring is selected
it can be representing fractions of etrees,
eg, given a+b+c, a selection can include
all of term-b and partials of terms {a,c} .

. there may be parts of the given language where
partial terms don't have the same meaning;
ie, there would be nothing but a
char-string translation of the object selection .
. in any case,
the quickest, most general way to define a selection
is to get links to the entire chain of symbol tables;
and, copy the entire subtree that contains
all the fragments of the selection;
then include a descriptor that shows
where the selection is beginning and ending .

. when would you want fragments and still want
the etree object rather than a char string?
for orthogonality,
we have to provide for the possibility
that one of adde's plug-in app's
can find some use for such a selection;
ie, in many cases of user interaction
the selection is for a function other than
cut or copy .

7.15:
. when designing the pointer that is
going from etree nodes into symbol tables,
there must be an efficient coding,
and it should support efficient copying
even when it involves context changes .

. both the source and destination of a copy
have scope paths:
if the scope paths aren't the same
we have to identify any scopes not shared
and copy their symbol tables
for merging with the destination .
if this is a cut instead of a copy,
there are fewer choices,
since the destination space is smaller .

. a complication of multiple nestings of scope
is the orphaned symbol from ancestor scopes:
these imply some sort of communication with
a context which no longer exists .
. we have to remind the user
that the orphan's place in the destination
may need special attention:
should it be added to the new parent scope,
or some higher scope ?
. the default location would be relative height,
ie, the same number of scopes up the path
as it was in the source location .
. in any case, we have to assist the user
in keeping track of these orphan relocations,
and make sure that all affected contexts
are adjusted to create a sensible communication
such that, the role of the source ancestor
is now provided by the new context's procedure .

tags, link-trees, and file-trees

7.3: 7.30: adde/tags, link-trees, and file-trees:
. how to integrate tags with folder systems?
placing a file in a folder is tagging it;
 a hierarchy is a tag with segments;
ie, each path name is one tag .
. while a file can be in only one folder,
it can be assigned to many tags .

. tags can be thought of as
a list of links to its members;
and, equivalently, as attributes of a file:
each file or file link can list all the tags
to which it is a member,
just as it can tell the folder path it's in .

link-trees vs file-trees:
. a file-tree is the usual folder tree,
it contains actual files rather than links;
so, a file can be a member of only one file-tree .
. the link-tree is like a file-tree
except it contains only links to files
rather than actual files;
thus, a file can belong to many link-trees,
and may be in many places
within the same link-tree .
7.30:
. the main idea for these distinctions
is that file-trees are low-level concerns;
the only reason they need to be accessed
is when the space limits require
deletions or archiving .
. most file system operations
are concerned only with organizing files,
not managing limited space,
and each activity should have its own
customized view of the file system;
so, most file accesses should be done
through link-trees .
. tags can be applied to either files or links,
depending on the tag's scope:
tags on files are global;
tags on links apply only to
a specific link-tree;
ie, each link-tree has its own set of tags:
both the ones induced by the global tags
belonging to files it's linking to,
and the tags specified by the
user of the link-tree .

binary operation aggregation

7.10: adda/cstr/binary operation aggregation:
. biop's (binary operations)
can be seen as aggregated
by a rule book showing combinations of biops
that should be considered to be
one subprogram call
ie, binding to a particular subprogram;
eg, {?, else} are both biops,
and the rule book would say that
(?, else) is a single function:
?-else(truth,proc,proc).proc
or ?-else(truth,fun,fun).fun .

references for security and speed

7.9: adda/oop/references for security and speed:
. notice how oop would rather
create a new object and modify a pointer
than modify the value of a current object .
. I call this the "(pervasive pointers).

. from an encapsulation view there is no diff',
since only the owning type
can do these mod's .
. what it does seem to uniquely do though,
is encourage the sharing of objects;
ie, if you can modify your value
then I have no interest in sharing its object
because it's no longer synonymous with
the intended value at some past time .
--
. oop is doing for every value
what c does only for arrays .
7.10:
. it does promote strong
capability-based security;
because if everything is through reference,
and ref's are encryptable,
then that is a much stronger encapsulation
unless the system is already protected
by allowing only system-compiled code .
7.11:
. another interesting property of
pervasive pointers
is that by comparing pointers,
one can tell quickly whether
even huge structures are identical;
though if the pointers aren't equal,
they might still represent equal values .
. python has a speed hack where the
first 100 ints have reserved pointers
so in the many loops controlled by small ints,
pointer compares are decisive .

local resource accesses and wrappers

7.3: adda/portability/local resource accesses and wrappers:
. wondering how adda can provide portable features
and yet also provide access to
individual platform features .
. per each platform,
represent its features as a library,
and then map adda's features to that .
. users can expect portability from
staying with the model;
and can get more into their specific platform
by importing the lib's it offers .
. additionally,
there will never be a portable model of
what paths you can modify;
instead, you have to list per system,
what volumes are available,
and whether they are writable or rom .
7.5:
. adda must include all the storage models,
and must map them to diversely contstrained models:
eg, some platform may offer nothing but a database,
so, adda must provide a hierarchical filesystem
that is implemented by a database .

go's defer statement

7.1: adda/go.lang/defer:
. go.lang has a defer
that is like a type mgt's finalization routine
only it's used by a function
for things that should happen on return .
. ideas I got from that are:
# on return: ... [7.30:
. "(on *condition*) would generally mean
rule-based vs imperative programming;
so (on return: s) would add (s) to
the list of things to do before returning .]
# self`end`+ ... [7.30:
. this is modeled after i`+ 1
which is shorthand for i= i+1 .
. the self is the current subprogram;
it already has an "(end)
listing things to do before ending;
and a (`+) would add to that list .]

Ousterhout's dichotomy

7.1: news.adda/Ousterhout's dichotomy:
. John Ousterhout, designer of Tcl,
noticed that high-level programming languages
tend to fall into two groups,
"system programming languages"
and "scripting languages".
[ie you can't have a language that is
optimal for both .
. in defence of that claim,
pypy tried to have a system language Rpython
that was as much as possible like
Python, the scripting lang;
because they wanted
a self-hosting python compiler
ie, one written in python instead of c .
[7.30: like adda,
Rpython is designed to translate into c
for the purpose of avoiding c:
system programmers can use Rpython
yet still take advantage of c compilers .]
. the closest Rpython could get to python
is a subset of it that added static typing;
because, some features that support
coder productivity
are antithetical to features that support
algorithm efficiency .
. Ousterhout was likely pointing out that
scripting lang efficiency was not so important;
because, scripts are glue for
subprograms of sufficient size,
such that most of the run time
is spent in the parts defined by the system lang .
7.30: web:
D. Ancona, M. Ancona, A Cuni, and N. Matsakis.
RPython: a Step Towards Reconciling
Dynamically and Statically Typed OO Languages.
In OOPSLA 2007 Proceedings and Companion, DLS'07:
Proceedings of the 2007 Symposium on
Dynamic Languages, pages 53-64. ACM, 2007(pdf)

. an approach that attempts to preserve
the flexibility of Python,
while still allowing for efficient execution
is limiting the use of
the more dynamic features of Python
to an initial, bootstrapping phase.
This phase is used to construct
a final RPython (Restricted Python) program
that is actually executed.
RPython is a proper subset of Python,
is statically typed,
and does not allow dynamic modification
of class or method definitions;
however, it can still take advantage of
Python features such as mixins and
first-class methods and classes.
This paper presents an overview of RPython,
including its design and its translation to
both CLI and JVM bytecode.
We show how the bootstrapping phase can be
used to implement advanced features,
like extensible classes and generative programming.
   

enum.typed record domains

6.20: adda/dstr/enum.typed record domains:
. in classic lang's like c,
arrays had very different properties
than records .
. in a polymorphic languages however,
records can be more like arrays;
because, although their components vary in type,
the various types often have the same base type;
eg, all types can print their value, etc .
. and any time a record has at least
2 components of the same type,
it could make sense to specify components with
an expression rather than a literal name,
just as is done for arrays .
today's issue is this:
. in trying to unify the concepts of
arrays and records,
there needs to be a way for records to
express their component names as being
some enumeration-type's subrange;
and then, conversely,
any time a record r declares its components' names,
that should induce an enumeration type:
r`domain
-- I'm using the term "(domain) because
arrays and records are like functions;
and, functions in math are known to
input values from a domain type
and output values from a codomain type;
ie, f: domain -> codomain;
or, in adda:
function f(x.domain).codomain,
array A#(domain).codomain
record R.(r1.co1, r2.co2, r3.co3);
R`domain = {r1, r2, r3};
R`codomain = {co1.type, co2.type, co3.type},

. assume there's the enumeration
e.type: {r1, r2, r3};
how should a record say its domain = e ?

R.(r1.co1, r2.co2, r3.co3);
R`domain`= e ?
[6.23: yes,
that lets the record be defined in the usual way,
and then also say that the domain is
not a new declaration,
but rather a reuse of some existing enum.type .]

mis:
. one thing that wouldn't work is this:
R#(e).{co1.type, co2.type, co3.type} ?
-- that would instead be saying
R is an array of enum;
and each var's possible values
are in the set:
{co1.type, co2.type, co3.type}.
--. this could be useful for when
writing programs that write programs:
many of the values they're concerned about
are parts of languages, including types .

preventing insecure inputs

6.11: adda/abi/insuring security:
[6.13: intro:
. many app's are a security threat because
they are trusted not to smash the stack or heap,
yet will do so if given mal-formed input;
the primary security defense provided by adda
is that all interactions with the stack or heap
are handled by robust system app's .]

. an app may be expecting ascii
and get unicode instead,
but adda typetags would document what was there,
and then the app could take steps to
convert to the prefered type .
[6.24:
. non-native types can have novel structures;
but they are always compositions of
native elemental type;
and, the addx system is helping app's
to read and write the data they exchange .]

oop's multi-dispatch

6.5: adda/oop/multi-dispatch/ working with obj'c:
[6.17: intro:
. according to the wiki,
the term"multi-dispatch refers to
something other than what I assumed it to be
so, I will now explain the diff's .

. everybody agrees on how polymorphism happens
when there is only one argument:
when you write f(x) you mean
x can be any type as long as
x's type defines a function f .
. you don't really know which procedure or method
is being used to define the function f
until you ask x what its type is,
then you use the f-procedure defined by that type .
. that is called dynamic dispatch;
the term "(dispatch) is being used in the same way
as "(taxi dispatcher),
whose decision of which taxi to send
depends on which taxi is free and closest;
likewise, a function call dispatcher
determines which procedure to send the arg to,
and bases its decision on
both the function name,
and the argument's type .

. if the arg is binary,
then a multi-dispatch system has to find
a procedure that is typed for that particular
combination of arg types;
and most such systems use function overloading;
ie, they overload a function's meaning;
eg,
there are many types of cars and motorcycles;
and how a collision turns out
depends on both types;
so then, for each type combination,
you have to define a new procedure
for the car-motorcycle collision function;
that means, for example,
that every time you create a new type of motorcycle,
you have to define as many new collision procedures
as there are types of cars .

. the multi-dispatch system I have in mind
does not use overloading;
rather it expects multiple args to share some supertype;
so, for the cars and motorcycles example,
they could simply share the physics type;
which defines its members as having
a mass and a velocity;
the collision procedure asks both arg's
for their mass and velocity
and then calculates new velocities for each .
. it then sends each arg a message
to change itself to the new velocity,
which each can do with its own version of
a velocitychange(x) procedure .

. that was a simple case because the multi-arg function
could be reduced to a multiple of single-arg functions;
a more complicated case can be found in numerics,
where a binary operation doesn't resolve into
2 unary operations;
. for example, say you had a numeric supertype
that includes only reals and ints;
# it can be overloading the addition function:
+(int, int),
+(real, real)
+(real, int),
+(int, real) .
# or it can use coercion:
it checks to see if types differ,
and then converts one
so both are the same type:
+(int,real) then means a call to
+(real,real);
it then checks whether the destination
is able to accept a real,
or if the destination has a function for
converting a real to its own type .

. now lets say another type, Rational,
is declared to be a subtype of numerics;
this means the supertype procedure for
handling binary operations
has to be updated:
# overloaders then have many more cases to deal with:
{int,real,rational}
x {int,real,rational}.
= 9 cases instead of 4 .
# coercers have another rule to add:
if types differ, then convert ... to ...:
{int,real} to real
{int,rational} to rational
{real, rational} to real .

. in the case of numerics there is a limit to this:
every imaginable subtype of numeric
can be expressed as subtypes of
just these subtypes:
{int, real, rational, complex}
x size-{1,2,4,8byte, huge};
so, for example,
we can declare rainbow to be a subtype of real,
and then the numeric supertype can
-- without ever knowing about rainbows --
see from its type declaration
that it must have a
convert rainbow to real procedure;
and, if a destination is type rainbow,
it again knows from the rainbow declaration
that this destination
has a real assignment procedure .
]-intro
[6.8: 6.17:
. as part of developing for mac,
obj'c features the usual dynamic dispatch .
. the sort of multi-dispatch I have in mind
would fit within mac's type-tagging system;
so for instance,
numerics would have 2 type tags:
# one says it's a subtype of mac's NSobject,
# another is private and indicates
which subtype of numeric it currently is .]

alloc'order and size

6.2: adda/mem'mgt/alloc'order and size:
. when using the c lang's dynamic mem'allocator (malloc)
the c`runtime assumes you will be
returning mem in mostly the same order as
when you obtained them .
. if this is not the case,
then there could be heap fragmentation problems .
[6.3:
. use of malloc order may be less complicated
because in modern systems there is v.mem,
so the parts of heap that are
in the way of compacting it
can simply be paged out .]

. the less mem you use at any one time,
the better chance buggy programs around you
don't blow up from exceeding mem limits .

. if needing to alloc mem in a way that could
cause heap fragmentation,
consider how much mem your program is using at once,
and whether you can break it into pieces
that do inout on temp files .

6.17: other strategies:
# at the app level:
. it's easier to find mem even in a fragmented heap
if you're decomposing your mem needs into smaller parts;
eg, instead of alloc'ing 100 contiguous words
for a 10x10 matrix,
you could do 10 alloc's of 10 words each
arranged as an array of pointer to arrays .
# at the os level:
. just as logical files are strings of
many non-contiguous physical mem blocks;
malloc could be impl'ing large mem requests
as strings of smaller mem blocks .

oop storage classes

6.1: adda/type/storage classes:
. recently it was seen how oop's class var's
can be modeled by having vars declared in
the interface type mgt's body
(the implementation module of the interface).

. the same idea can apply to declaring agg' types
(aggregates include the arrays, and records)
which can be just like an interface type
except that an agg's specification can't
declare new operators; [6.20:
ie, the definition of an interface type
is a type that declares
what operations and components
can be applied to obj's of this type;
an agg type is one that need declare only
components .]

. both the {agg', interface} type def's
can declare these 3 storage classes:
# public instance components:
in the typedef's face .
# private instance var's:
in the optional initialization function,
within the typedef's body .
# private class var's:
in the typedef's optional body .

efficiency concerns:
. if the type's face (ada`specification)
doesn't have to declare privates,
then the compiler can never know
what the actual size of an object will be;
whereas, if the face can include
something like: '(privates:0),
then the compiler can potentially know its size .
. however, given the trailer idea
(dynamically extending local mem),
knowing the size is not important anyway:
all act'rec's would have a discriminant bit
indicating the primary record variant:
the one {with, without} a pointer to trailer .
. if with trailer, then any private instance var's
would be on the trailer at that index .

6.1: adda/{begin, end} rename {init,fini}callbacks:
. what I've been calling the {init, fini} routines
should be named {begin, end}
since they mean the same thing in plain english .

a brief history of compound documents

5.7: web.adde/compound doc/problems:
. the compound doc is a really simple idea;
it works just like the way that your mac's gui
displays a window of various apps,
except that window arrangments can be
saved as documents, and windows can be borderless
as if they are part of the same document .
. but from reading opendoc's history
you'd think it was a plague .
"(. compound documents are said to be
an oversold concept:
there just aren't that many examples
beyond mixing graphics with text .)
--
. tell that to the html`object tag:
we routinely see combinations of
movies, photo's, text, script images,
and anything you have an app for .

. an amazingly bad specification or implementation
was opendoc's biggest problem:
it was very common to find
apps that could not even
open a document created by another app .
. OpenDoc attempted to solve this problem by
allowing developers to store multiple formats
to represent the same document object.
For instance, it was both possible and encouraged
to store a common format like JPEG
along with an editable binary format,
but in practice few developers
followed this recommendation.

--
. something about the plague again:
other compound doc specifications
had the same problem!
. the specification should have included
a manifest that listed what app's you need
in order to open a given document .

more compound doc' technology is history:

Dynamic Data Exchange (DDE, 1987),
allowed "conversations" between applications.
OLE(1991, (Object Linking and Embedding).)
was Microsoft's first object-based framework,
and MS`Office's first compound doc' technology;
it was built on top of DDE .
. While OLE 1 was focused on compound documents,
COM and OLE 2 (1992-93) were designed to address
software components (oop++) in general.
. OLE custom controls (OCXs, 1994)
. Internet is a new use for
OLE Custom Controls (ActiveX, 1996),
-- gradually renamed all OLE technologies to ActiveX,
except the compound document technology
that was used in Microsoft Office.
DCOM (Distributed COM, 1996)
competed with CORBA as the model for
code and service-reuse over the Internet.
difficulties getting either of these
over Internet firewalls .
MTS run-time increased scalability, robustness,
and simplified system management.

. ms`COM is often an umbrella term for
OLE, OLE Automation, ActiveX, COM+ and DCOM .

[ com is oop++ ]
COM's architect"Anthony Williams:

Object Architecture
is concerned with Dealing With the Unknown
and ensuring Type Safety in a
Dynamically Extensible Class Library;
also significant to com
was clarifying what oop`Inheritance is,
and knowing How To Use It .

Charlie Kindel 1997:

(popular) oop =
Polymorphism + (Some) Late Binding
+ (Some) Encapsulation
+ Inheritance

Component Oriented Programming (cop) =
Polymorphism + (Really) Late Binding
+ (Real, Enforced) Encapsulation
+ Interface Inheritance
+ Binary Reuse” .

C++ supports only oop not cop
so, COM must additionally specify:

* Execution environment options
(so-called Apartments)
* Inter-process Marshalling
* Remote Object Activation mechanism and protocols
* Threading models

. the C++ linkage model impedes
binary distribution and reuse .
. by using shared object linking,
the lack of binary standardisation
means there is an interoperability problem .
C++ lacks binary encapsulation:
ie, while it supports separation of
interface and implementation,
it's only at the syntax level
– not at the binary level.
implementation changes are “seen” by clients.

com provides what c++ is missing:

A “substrate” for building re-usable components.
. Interfaces are defined in COM IDL
(IDL + COM extensions for inheritance and polymorphism)
OS Neutral and (nearly) Language neutral:
. can be used from any language that can
generate/grok vtbl’s and vptrs.
. a packed bit field is returned
with every COM access .
categories define
an implementation of a given interface
that meets some set of constraints .