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authorbryan newbold <bnewbold@robocracy.org>2010-02-16 13:49:22 -0500
committerbryan newbold <bnewbold@robocracy.org>2010-02-16 13:49:22 -0500
commit14fd1caae8924a0c9fba43337c6ed47b26ba61e6 (patch)
treecd6af9f39f367f25d992b1b6f44cd60b12ba6822
parent5c8148df01fe38cb1e5bc05b9013712358661c35 (diff)
downloadknowledge-14fd1caae8924a0c9fba43337c6ed47b26ba61e6.tar.gz
knowledge-14fd1caae8924a0c9fba43337c6ed47b26ba61e6.zip
ralt to meta trick
-rw-r--r--software/haskell.page27
-rw-r--r--software/unix-tricks.page9
2 files changed, 36 insertions, 0 deletions
diff --git a/software/haskell.page b/software/haskell.page
index 6911315..8e7d9f8 100644
--- a/software/haskell.page
+++ b/software/haskell.page
@@ -21,6 +21,33 @@ lines indented to the same position as the first non-whitespace after the
stuff1
stuff2
+Lists
+--------
+Lists in haskell are homogenous: all elements must of the same type. They are
+linked lists, so cons-ing on the front is cheap and concatonating on the end
+can be expensive.
+
+Use ++ to concatonate two lists together:
+
+ ['a','b','c'] ++ ['d','e','f']
+
+Use : to cons (prepend) a single element:
+
+ 0:[1,2,3,4,5,6]
+
+Use !! to pull out an element by index (zero indexed):
+
+ ['c','a','t'] !! 1
+
+Strings are lists of characters: "baby" is equivalent to ['b','a','b','y'],
+which is equivalent to 'b':'a':'b':'y':[]. The empty set is [] and is distinct
+from [[]].
+
+A couple functions help; 'head' is like 'car' and gives the first element,
+'tail' is like 'cdr' and gives everything except the first element, 'last'
+gives the last non-empty element, and 'init' gives everything except the
+'last'. 'length' gives the number of elements, 'null' is a test to see if this
+is the empty list,
Compilation
------------
diff --git a/software/unix-tricks.page b/software/unix-tricks.page
index 533a174..41bda41 100644
--- a/software/unix-tricks.page
+++ b/software/unix-tricks.page
@@ -16,3 +16,12 @@ To fork off 10 instances of sleep with incremented lengths, 5 at a time::
$ seq 10 20 | xargs -n 1 -P 5 sleep
+Remapping a Keyboard Key to Meta
+-----------------------------------
+I like having a Meta key (aka "Windows key") for use with system keyboard
+shortcuts (change desktop etc), but some laptop keyboards don't have an extra
+button. To remap one of the Alt keys, you need to know it's code: on FreeBSD
+6.3 it was: ``Alt_R keysum 0xffea keycode 113``. To get the right mapping under
+X11, read the directions in ``/usr/X11R6/lib/X11/xkb/README``. To get the right
+mapping under the console, edit ``/usr/share/syscons/keymaps/us.iso.kbd`` and
+change 'ralt' to 'meta'.