diff options
Diffstat (limited to 'software')
| -rw-r--r-- | software/functional programming | 52 | ||||
| -rw-r--r-- | software/git | 7 | ||||
| -rw-r--r-- | software/ruby | 67 | ||||
| -rw-r--r-- | software/scheme | 67 |
4 files changed, 193 insertions, 0 deletions
diff --git a/software/functional programming b/software/functional programming new file mode 100644 index 0000000..4720280 --- /dev/null +++ b/software/functional programming @@ -0,0 +1,52 @@ +=================================== +Functional Programming +=================================== + +Recursion +-------------- +**Partial** functions can recurse endlessly over a finite input. **Total** +functions will terminate/halt over a finite input. (TODO: check this +definition) + +Collectors +-------------- +The collector concept/pattern/paradigm is the one I am least familiar with +in functional programming. + +My current understanding is that they essentially allow allow recursive +functions to maintain something like state by wrapping immutable functions +or variables in layer after layer of functions and just holding on to +the outermost layer. For instance, the typical way to write a ``length`` +function in python would be:: + +>>> def how-long(x): +>>> l = 0 +>>> while x.has_next() +>>> l = l+1; +>>> x.pop() +>>> return l + +Using recursion, we could do:: + +>>> def how-long-recurse(x): +>>> if x.has_next() +>>> x.pop() +>>> return how-long-recurse(x) + 1 +>>> else +>>> return 0 + +Using the collector paradigm, we could do:: + +>>> def add1(x): return a+1; +>>> def how-long-col(x, col): +>>> if x.has_next() +>>> return col(0) +>>> else +>>> x.pop() +>>> return how-long-col(x, lambda a: col(add1(a))) + +The first two ways, the plus one operation is actually executed at any given +time, while with the collector implementation we're really creating a +function step by step which will give the answer at the end when it is all +executed. + diff --git a/software/git b/software/git new file mode 100644 index 0000000..cd0da69 --- /dev/null +++ b/software/git @@ -0,0 +1,7 @@ +======================= +Git +======================= + +Quick tip: when you have ``.gitignore`` ignoring everything (with a ``*`` +entry), you need to use ``git-update-index --add FILE`` to actually add the +file, instead of just ``git-add FILE``. diff --git a/software/ruby b/software/ruby new file mode 100644 index 0000000..e64f73e --- /dev/null +++ b/software/ruby @@ -0,0 +1,67 @@ +================== +Ruby +================== + +.. note:: This information is very rough, it's mostly my notes about what is + different about Ruby syntax compared to similar modern interpreted + pan-paradigm languages like Python. + +A unique intro to ruby is `"Why's Poignant Guide to Ruby"`__, a web-comic-y +short free online book by why the luck stiff. The more serious reference is +the "pickax" book. + +__ http://poignantguide.net/ + +Blocks +--------- +Blocks of code can be passed to functions, making ruby code more of a first +order data type. + +Ranges +---------- + +>>> 2..7 # => 2..7 +>>> (2..7).to_a # => [2, 3, 4, 5, 6, 7] +>>> (2...7).to_a # => [2, 3, 4, 5, 6] +>>> ('e'..'h').to_a # => ["e", "f", "g", "h"] + +Control Structures +-------------------- +Can use ``if`` after a statement:: + +>>> a = c if c > b + +Along with the usual ``break`` and ``next``, there is ``redo`` which redoes +the current loop (initial conditions may have been changed). + + +Boolean Operators +-------------------- +Anything that is not ``nill`` or ``false`` is true. To force interpretation +as boolean, use ``!!`` (not not):: + +>>> !!(nil) # => false +>>> !!(true) # => true +>>> !!('') # => true +>>> !!(0) # => true +>>> !!({}) # => true + + +Misc +---------------- +Can use nasty Perl style regular expression stuff:: + +>>> re1 = /\d+/ +>>> "There are 5 kilos of chunky bacon on the table!" =~ re1 # => 10, the index +>>> $~ # => #<MatchData:0xb7c36754> +>>> $~.pre_hash # => "There are " + +Also $1, $2, etc. + +The "splat operator", '*', either collects or expands extra arguments depending +on syntax (I think this is kind of icky):: + +>>> a, b = 1, 2, 3, 4 # a=1, b=2 +>>> a, *b = 1, 2, 3, 4 # a=1, b=[2,3,4] +>>> c, d = 5, [6, 7, 8] # c=5, d=[6,7,8] +>>> c, d = 5, *[6, 7, 8] # c=5, b=6 diff --git a/software/scheme b/software/scheme new file mode 100644 index 0000000..258343b --- /dev/null +++ b/software/scheme @@ -0,0 +1,67 @@ +================== +Scheme +================== + +``mit-scheme`` with the ``scmutils`` package is assumed; the command +``mechanics`` starts in interactive edwin prompt. + +See also notes on `The Little Schemer </k/books/littleschemer/>`__. + +Scheme Implementations +----------------------- + +Very partial list, mostly just the ones which are interesting to me. + +MIT/GNU Scheme + The 7.9.0 release (last stable as of 01/01/2009) is not R5RS compatible, + and is generally a pain in the ass to compile on new systems. The 9.0 + release should be easier to compile and distribute because it will use + a C compiler to bootstrap (true?). + +SCM + SCM is a fairly minimal, very small footprint R5RS-compatible + implementation. Apparently very portable and easy to compile. Includes + the Hobbit compiler. Part of the GNU project, maintained at MIT? + +SIOD + SIOD (scheme in one day) is a super small (75k binary?) Scheme + implementation. + +Coding in ``edwin`` +----------------------- + +..note: this section should be spun off as emacs. edwin is essentially a + scheme version of emacs. See this + `http://static.bryannewbold.com/mirror/sheets/emacs.pdf`:emacs cheatsheet: + +Common keyboard commands (usually 'M' is alt button, 'C' is ctrl, and 'S' is +meta/super/"windows"): + +========= ==================================================================== +C-x C-f Open a file, or create a new one +C-x C-s Save the file +C-x k Kill (close) a buffer +C-x C-c Exit the editor +C-g Abort a command +C-x C-e Evaluate the previous expression +M-z Evaluate the surrounding expression +M-o Evaluate the entire buffer (everything) +C-c C-c Kill evaluation after an error +C-y Paste (yank) +C-x 2 Split screen vertically +C-x 5 Split screen horizontally +C-x o Switch to next buffer window +C-x 1 Return to non-split screen +M-x Enter a command by name in minibuffer (use tab to complete) +C-x C-b Show buffer menu +C-x b Select buffer +C-x u Undo +C-y Paste +========= ==================================================================== + +Scope +-------------- + +``set!`` looks up a symbol name and permanently changes the first value it comes +across. ``let`` (and ``letrec``) create a new symbol with the given value. +But wait, you need a ``lambda`` block to make everything work? |