“If I was stranded on an island and the only way to get off was to write a UI, I would die.”
– Linus Torvalds
Category Archives: Uncategorized
Minecraft circle creator
I am spending some time revisiting and documenting some of my favorite php solutions. They are all very light-weight and flexible. This first one is a minecraft circle generator. You are supposed to pull up a circle size and then use it as a template in minecraft. As you build levels upon levels, you will create large domes.
Here is an example of just starting out on the side of a hill.
The law is like a programming language
Programing languages are made up of little functions, one might pop up a box that says: “Do you really want to quit?” and will have little “Yes” or “No” buttons. You really would imagine that this would lead the program to end, but depending on how the function is written, it might not necessarily do that. It might assume that the programmer is going to make the thing end some other way. In fact, it could be made to fire up the printer. That would be really strange, but it could easily be done.
Now imagine that the total body of laws is like a computer language and that the little piece of the program (function) that asks if you want to quit is like a new piece of legislation. It could be used in unexpected, and even nonsensical, ways if judged and lawyers concluded that it could. Imagine if some law accidentally gave a legal advantage to people who periodically blew a bugle when publicly speaking. Thousands of bugles would be sold and used, no questions asked.
So if we can begin to see the law as amoral (neither moral or immoral), then we can best make use of it. This is especially true for laws regarding religion. As the conservative Supreme Court and state governments roll out more laws protecting religious freedom, expect more and more groups making odd claims to being religious. The problem is that if they build their case correctly, like a computer program that acts strange but doesn’t crash, then they “will” legally be religious. Strange days are sure to come.
Hacker Challenge/online SVG creation tool
Hacker Challenge:
I have created a little online tool that creates SVG images that can be sent to the laser printer. It is built on top of bash and so can do stuff in a pretty clear way that you can’t quite do with other tools that I have found. The example below shows off nested loops, variable assignment, and function creation. Because it is generally considered a HUGE security hole to allow shell access from cgi, I have tried to make this as secure as possible. I have even gone so far as it isolate it (for now) into its own domain and site. I have used restricted shell and allow access to a directory that only has ‘bc’ and ‘sed’ in it (which I show in the example). Can anyone point out how the nefarious hacker could foil this? Also, feel free to play with it and try to print from it. It seems like now you have to save into inkpad and create a xps file, but I printed this image out the other day. I will stop working on this site and branch off another one for development since most websites don’t change as the hacker tried to get in. Also, the real-time graphics only work in firefox, probably a minor coding error to get them to work in IE. (Someone already asked about javascript, I think that might be a way to do it, perhaps with a buffer overflow).
Go to the challenge
What every programmer should ask when designing a new language
Here are some questions a prospective language designer should ask
himself when starting the designing a programming language.
– What need are you trying to fill? Don’t fall into the trap of “a
scripting language”, because they always turn into general-purpose
languages.
– What’s the metaphor? Even though you might not be trying to build a
“pure” language, it’s worth having a model for the core language,
such as “imperative, block-structured” (C), “object oriented”
(Smalltalk), “generic object orientation” (Lisp), “functional” (ML),
“lazy” (Haskell), “logic” (Prolog), “production system” (OPS5), etc.
These different core models influence the “natural” styles of program
development in different languages even if the set of available
facilities is similar. They also help define which late-arriving
features will “fit” and which will be warts.
[Jerry Jackson]
– How many programming paradigms does your language support? How tightly
are they integrated? Which other paradigms can you integrate with the
built-in facilities? How natural is the syntax of user-defined
extensions? Many problems are much better suited to some non-standard
programming model than to the usual object-oriented/functional
approaches. For example, constraint languages allow a very concise
description (and efficient solution) of many optimization problems.
Dylan supports functional and object-oriented programming in a tightly
integrated manner, but it offers no support for non-deterministic
programming, constraint-solving, etc., and not much support to add them
to the language. If you have first-class continuations in the language
you can add one additional programming model that requires non-standard
control flow, but, in general, different extensions based on call/cc
don’t work together.
[Matthias Holzl]
– Is high performance an issue? This says something about whether you
want to implement an interpreted, a VM-based, or a natively compiled
language.
– Is high programmer productivity an issue? How important is this with
respect to performance? This decision can affect how you store
values and do function calling.
– How portable across platforms do you want the language to be? This
will relates to whether you want to compile to a VM or to machine
code, and to how well you support native libraries. It will also
affect library design for such things as graphics and GUI tools.
[Anton van Straaten]
– Do you want easily distributed executable code, i.e., do you you want
to allow code to be easily transmitted across networks and run
elsewhere, as Java does? Do you want to provide built-in support for
remote execution, like RPC/CORBA/RMI? If you are writing for a VM,
this can simplify some of these issue considerably.
[Anton van Straaten]
– What about debuggability? If you plan to compile it, you need to
think about how to store debugging information.
– How do you want to bootstrap it? This, too, says something about
what kind of back-end you might build. Perhaps you build a tiny VM
in C, then compile to C. This way, you avoid fun but time-consuming
work on code generation for modern super-scalar hardware, register
allocation, etc.
– Do you want to be able to catch type errors early or late? That says
something about your type system (whether you require that all types
be statically declared at compile-time, or allow them to be dynamic,
or have a hybrid scheme like Dylan does). In addition to the obvious
effect on performance, this decision will affects your memory model
in that completely static systems do not require tags or boxing.
– Will variables be associated with explicit type declarations?
– If yes, will these type declarations be required or optional?
– If optional, will the language use inferencing to supply unspecified
types, or simply use an all-purpose type (like Object or ‘any’)?
[Anton van Straaten]
– Will the language have any run-time type discrimination/checking at
all, or will types be completely statically determined? Some
languages considered statically typed still do some run-time checking,
such as Java.
[Anton van Straaten]
– Will any type checking happen at compile-time? Some languages with
explicit type declarations don’t always check types at compile-time,
such as old Visual Basic.
[Anton van Straaten]
– If you allow type declarations, you will want to think about whether
you want parameterized types. If you go whole hog with, say, F-bounded
polymorphism, you can get performance *and* type safety *and* ease of
use, but it’s hard to get this exactly right.
– What about namespaces? Do you want to have a simple scheme as in
Java, where classes, namespaces, and files are roughly equivalent?
Lisp-style packages? Dylan-style modules and libraries? Within a
single first-class namespace, how many second-class namespaces are
there? Java has 7 or 8: class names, function names, local variable
names, slot names, etc. Common Lisp has at least 3 (function,
variable, and class names). Dylan and Scheme have one, which greatly
simplifies things at a small loss of generality which can usually be
worked around with name conventions.
– What about encapsulation? Do you want to do information-hiding on a
per-class basis as in C++ and Java, or on a “module” basis as in Dylan?
– Is your language a functional language (that is, without side-effects)?
If so, is it an almost-functional language or a true pure functional
language? Or is there a functional core with some sort of machinery
for isolating side-effects, like monads do in Haskell?
– What kind of evaluation semantics does the language have? Eager as
in most languages, or lazy as in Haskell?
– Is your language purely lexical or do you offer dynamic variables (or,
more generally, access to the dynamic environment) as well? Dynamic
binding allows you to introduce local state for the duration of a
computation without side effects and without adding additional
parameters.
[Matthias Holzl]
– Are there different semantics for “pointer-ish” and “non-pointer-ish”
values, like in C? Or is everything a first-class object reference,
like in Lisp? Having multiple ways of referencing values can make the
user mode much more complicated. On the other hand, making everything
be object references can require boxing and/or tagging schemes that
make your compiler and FFI more complex.
– How do you want to pass arguments to functions? By name as in Algol?
By value or by reference as in C? By object reference like Lisp does?
Is there more than one convention in the language?
– Do you want first-class functions? What about lexical closures?
First-class continuations? The answer to those questions will tell
you things about heap- and stack-allocation, and will also tell you
how important it might be to do a continuation-based compiler. It
also tells you how hard your compiler has to work to avoid consing
environments unnecessarily. Lots of sophisticated language designers
go with simple closures and avoid full continuations, because
full-scale environment capture is hard to do well.
– Does your language have an unwind-protect like facility? When you
design a new language it is tempting to include call/cc because it
allows you to do define many common (and uncommon) control structures.
On the other hand you want to have a facility that allows you to
reliably relinquish resources after you are done. If you simply try to
combine call/cc and unwind-protect, you immediately get the
“impenetrable shield vs. unstoppable force” problem in your language.
Possible solutions include: no call/cc, weakened unwind-protect,
different semantics for call/cc.
[Matthias Holzl]
– How do you handle conditions/errors? Return codes or signalling? Do
you have an unwinding-only model like C++/Java or do you allow restarts
like Dylan/CL? If you do the latter do you separate conditions and
restarts like Common Lisp or do unify them like Dylan? These questions
are important, because every programming language has to deal with error
conditions, and in many cases the unwinding model is used simply because
the language designer is not aware of any other possibilities.
[Matthias Holzl]
– Do you want the language to be “object-oriented” at all, given a
broad definition of OO that includes the spectrum from single
inheritance single receiver languages as in Java to multiple
inheritance multiple receiver languages as in CLOS? Do you want
to provide genericity through some sort of template scheme?
Here is how Jonathan Rees has characterized the very fuzzy term “OO”.
1. Encapsulation — the ability to hide the implementation of a type
2. Protection — the inability of the client of a type to detect its
implementation, guaranteeing that any changes to an implementation
that preserve the behavior of the interface will not break any
clients. This also gives some measure of “security”, because things
like passwords can’t leak out.
3. Ad hoc polymorphism — functions and data structures with parameters
that can take on values of many different types.
4. Parametric polymorphism — functions and data structures that
parameterize over arbitrary values, such as “a list of anything”). ML
and Lisp both have this. Java doesn’t quite because of its non-Object
primitive types.
5. Everything is an object — all values are objects. True in Dylan, but
not in Java because of its primitive types.
6. “All you can do is send a message” (AYCDISAM) = Actors model — there
is no direct manipulation of objects, only communication with (or
invocation of) them. The presence of fields in Java violates this.
7. Specification inheritance = subtyping — there are distinct types
known to the language with the property that a value of one type is as
good as a value of another for the purposes of type correctness. An
example is Java interface inheritance.
8. Implementation inheritance/reuse — having written one pile of code, a
similar pile (such as a superset) can be generated in a controlled
manner, that is the code doesn’t have to be copied and edited. A
limited and peculiar kind of abstraction. (E.g. Java class
inheritance.)
9. Sum-of-product-of-function pattern — objects are, in effect,
restricted to be functions that take as first argument a distinguished
method key argument that is drawn from a finite set of simple names.
Some people say Lisp is OO, meaning {3,4,5,7}. Some people say Java is
OO, meaning {1,2,3,7,8,9}. E is supposed to be more OO than Java
because it has {1,2,3,4,5,7,9} and almost has 6; 8 (subclassing) is seen
as antagonistic to E’s goals and not necessary for OO. The conventional
Simula 67-like pattern of class and instance will get you {1,3,7,9},
which many people take as a definition for OO.
[Jonathan Rees]
– If the language is object-oriented, do you want it to be class-based
or prototype-based?
[Steve Dekorte]
– If you’ve got an object system, do you want it to have first-class
objects that exist in the run-time? Should the object system extend
to include all the way to the primitive types, or do you want to
special-case those like Java does? Do you want a Smalltalk/Java-style
single receiver object orientation, or a CLOS-style multi-method
generic function dispatch? If the former, do you need some sort of
static overloading like C++ has? If the latter and performance is
important, do you need some sort of Dylan-style “sealing” so that you
can do some compile-time optimizations? Do you want single
inheritance, single inheritance with interfaces, multiple
inheritance, or a hybrid single inheritance with mixins? If you’ve
got a more static type system, you’ll need to deal with casts. Do
you additionally want auto-conversion?
– If you’ve got an object system, how much of a meta-object system do
you want to expose? Do you want it to be purely reflective, or more
than that? In Dylan, we separated ‘make’ from ‘initialize’, which
was a good idea, but do you also want to separate out ‘allocate’, so
that you have control over where an object is created, e.g., in a
“persistent memory” pool that might be back-ended by a database?
– Do you need hairy CLOS-style method combination, or is a simpler
style like we did in Dylan enough? Do you care about what Gregor
Kiczales calls “aspects”, which might change your decision?
– A more general question that relates to the object system, the
meta-object system, and a different dimension of the bootstrapping
question is: do you want to implement a language which provides a
bunch of predefined and fixed constructs (such as an object system)
or do you want to provide a layered language that implements such
constructs in terms of lower-level features in the language? The
former is probably easier, but the latter can allow very flexible
customization, which tends to be traded off against standardization.
Note that even a language with a powerful built-in meta-object system
won’t necessarily allow you to replace that object system with
something else, for example, unless the language supports that sort
of thing.
[Anton van Straaten]
– How do you want to do memory management, manual or automatic (GC)?
– Do you want to support threading? Do you want to roll your own
threads or use OS threads? Do you want to support massive
concurrency like Erlang does? The answers to those questions will
tell you about aspects of the run-time, memory allocation/GC, and
performance. Oh yeah — it also tells you if you can actually take
advantage of the multiple processors sitting in most of the machines
we all have. Do you want Java-style synchronization where it is
built in to objects, or should that be handled orthogonally?
– If you have threads and continuations, how do they relate to each
other?
– How well do you want to be able to integrate with native libraries?
This decision affects your memory model, how you plan to represent
run-time type info, how function call/return works, how signalling
works, etc. By “memory model”, I also mean to include what sorts of
objects are boxed or tagged. (Opinion: the Harlqn/FunO Dylan
compiler got it wrong — I think we should have boxed everything, and
then concentrated our efforts on box/unbox optimizations. This would
have *hugely* simplified FFI issues.) Good integration with native
code probably means that you will end up using a conservative
collector, and that will effect the semantics of “finalization” (if
you have it).
– Do you want to be able to return multiple values? How about &rest
arguments? These affect function call/return, tail-call elimination,
and stack vs. heap allocation optimizations.
– What’s your order of evaluation in expressions? This affects what
sort of optimizations can be safely done.
– What compilation model do you want? Lots of include files like
C[++]? Lots of “packages” like Java? Whole-worlds like Lisp?
Separate libraries like Dylan? This affects a lot of things, not
least of which is the ability to deliver small applications. It also
informs the design of your core run-time.
– Is the core run-time tiny like Scheme’s? Small like Dylan’s? Huge
like Common Lisp’s? If you like the Common Lisp model, it’s worth
looking at EuLisp to see how to re-package it in a more layered way.
– Even in a small run-time, you need to get the basic types right. Are
your numeric types “closed” (that is, do they include reals —
rationals and irrationals — and complex numbers)? Are your string
and character types rich enough to model Unicode?
– Think hard about collections. How do the following relate to each
other: sets, tables, vectors, arrays, lists, sequences, ranges? In
Dylan, we decided too late having the tail of a list be a “cons” was
maybe not such a great idea; what about that? How do your
collections interact with your threading model?
– Think hard about iteration, especially over collections. If all
collections obey a uniform iteration protocol, it means that you can
do things like ‘for e in c …’. Note that if iterators are done in
a first-class way, this has performance implications that your
compiler needs to worry about.
– Do you want some sort of security model built into the language?
What sort of model do you want to use? A simple “checker” like the
Java VM uses, or a more sophisticated capability-based model.
– What syntax do you want? Parentheses unaccountably give lots of
people hives, but S-expressions make a lot of things much simpler.
Infix syntax is quite nice when it’s done well, but you’ve got to get
the “kernel” of that exactly right if you want your infix macro
system ever to be usable. If you decide on S-expressions, should
they be represented as lists and conses, or do you want a first-class
object for that?
– Do you want to allow syntactic extensions (macros)? Lisp-style
macros? Dylan-style pattern-matching non-procedural hygienic macros?
Scheme-style ‘syntax-case’ pattern-matching procedural hygienic
macros? This says a lot about the syntax of your language, and it
also says a lot about the model you choose for compile-time
evaluation environments.
Thanks to Robert Eaglestone
Thingiverse
http://www.thingiverse.com/
Impress your co-workers with wheezak
When you don’t know what else to do, resort to the bs language of wheezak. Note, install wheezak on your servers when no one is looking:
Now just type a bit and act alternatively perplexed and satisfied as you communicate real time with the wheezak engine:
lsa
0000000 066163 060412
lsl
0000004 066163 066012
wheezak
0000010 073550 062545 075141 065412
smack
0000020 071555 060543 065412
dogta ( dsa )
0000026 062157 063564 060440 024040 062163 060440 024412
wheezak
0000044 073550 062545 075141 065412
smack
0000054 071555 060543 065412
^C
Convenient debugging with exit, unformatted data read
The following script is an example of two things. The first is how to preset a trap to do all of your cleanup, then you can exit anywhere in your script and it will still remove your temporary files. The other is just a silly idea using grep to handle unformatted data after the exit.
Script started on Fri 23 Sep 2011 02:46:04 PM CDT # cat traptest #!/bin/bash trap "rm $$.*" INT TERM EXIT # grep -v "#" $0 ls > $$.ls # exit # Everything after this will not be executed, # but the trap above will always clean up your temp # files, so you could use exit as a debugging tool You can type all sorts of stuff here and it will be displayed, but need not be echoed. # ./traptest You can type all sorts of stuff here and it will be displayed, but need not be echoed. # exit exit Script done on Fri 23 Sep 2011 02:46:14 PM CDT
AIX 6.1 requires additional parameters on Kerberos setups
In the file methods.cfg in /usr/lib/security the following lines need to be added.
KRB5A:
program = /usr/lib/security/KRB5A
program_64 = /usr/lib/security/KRB5A_64
options = authonly,is_kadmind_compat=no,tgt_verify=no
KRB5Afiles:
options = db=BUILTIN,auth=KRB5A
Then save the file. Should allow use of the previous setup.
Wrapping text around a string with sed & functionality
Need to use sed to do a string replacement.
This:
# Comments until end of line
Should be:
<span class=comment>#Comments until end of line</span>
This can be accomplished with sed by using the ‘&’ operator which pastes in the match space.
Script started on Mon 01 Aug 2011 04:47:45 PM CDT deadlycoffee:/tmp # sed 's/^#.*.$/(&)' test | sed 's/^#$/(&)/' (#) (#) (#) this is not a comment this isn't either (## This is) (# So is this.) deadlycoffee:/tmp # exit exit Script done on Mon 01 Aug 2011 04:48:52 PM CDT
In the above example, I do a much simpler replacement, but it is the same idea.