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view etc/MOTIVATION @ 665:fdefd0186b75
[xemacs-hg @ 2001-09-20 06:28:42 by ben]
The great integral types renaming.
The purpose of this is to rationalize the names used for various
integral types, so that they match their intended uses and follow
consist conventions, and eliminate types that were not semantically
different from each other.
The conventions are:
-- All integral types that measure quantities of anything are
signed. Some people disagree vociferously with this, but their
arguments are mostly theoretical, and are vastly outweighed by
the practical headaches of mixing signed and unsigned values,
and more importantly by the far increased likelihood of
inadvertent bugs: Because of the broken "viral" nature of
unsigned quantities in C (operations involving mixed
signed/unsigned are done unsigned, when exactly the opposite is
nearly always wanted), even a single error in declaring a
quantity unsigned that should be signed, or even the even more
subtle error of comparing signed and unsigned values and
forgetting the necessary cast, can be catastrophic, as
comparisons will yield wrong results. -Wsign-compare is turned
on specifically to catch this, but this tends to result in a
great number of warnings when mixing signed and unsigned, and
the casts are annoying. More has been written on this
elsewhere.
-- All such quantity types just mentioned boil down to EMACS_INT,
which is 32 bits on 32-bit machines and 64 bits on 64-bit
machines. This is guaranteed to be the same size as Lisp
objects of type `int', and (as far as I can tell) of size_t
(unsigned!) and ssize_t. The only type below that is not an
EMACS_INT is Hashcode, which is an unsigned value of the same
size as EMACS_INT.
-- Type names should be relatively short (no more than 10
characters or so), with the first letter capitalized and no
underscores if they can at all be avoided.
-- "count" == a zero-based measurement of some quantity. Includes
sizes, offsets, and indexes.
-- "bpos" == a one-based measurement of a position in a buffer.
"Charbpos" and "Bytebpos" count text in the buffer, rather than
bytes in memory; thus Bytebpos does not directly correspond to
the memory representation. Use "Membpos" for this.
-- "Char" refers to internal-format characters, not to the C type
"char", which is really a byte.
-- For the actual name changes, see the script below.
I ran the following script to do the conversion. (NOTE: This script
is idempotent. You can safely run it multiple times and it will
not screw up previous results -- in fact, it will do nothing if
nothing has changed. Thus, it can be run repeatedly as necessary
to handle patches coming in from old workspaces, or old branches.)
There are two tags, just before and just after the change:
`pre-integral-type-rename' and `post-integral-type-rename'. When
merging code from the main trunk into a branch, the best thing to
do is first merge up to `pre-integral-type-rename', then apply the
script and associated changes, then merge from
`post-integral-type-change' to the present. (Alternatively, just do
the merging in one operation; but you may then have a lot of
conflicts needing to be resolved by hand.)
Script `fixtypes.sh' follows:
----------------------------------- cut ------------------------------------
files="*.[ch] s/*.h m/*.h config.h.in ../configure.in Makefile.in.in ../lib-src/*.[ch] ../lwlib/*.[ch]"
gr Memory_Count Bytecount $files
gr Lstream_Data_Count Bytecount $files
gr Element_Count Elemcount $files
gr Hash_Code Hashcode $files
gr extcount bytecount $files
gr bufpos charbpos $files
gr bytind bytebpos $files
gr memind membpos $files
gr bufbyte intbyte $files
gr Extcount Bytecount $files
gr Bufpos Charbpos $files
gr Bytind Bytebpos $files
gr Memind Membpos $files
gr Bufbyte Intbyte $files
gr EXTCOUNT BYTECOUNT $files
gr BUFPOS CHARBPOS $files
gr BYTIND BYTEBPOS $files
gr MEMIND MEMBPOS $files
gr BUFBYTE INTBYTE $files
gr MEMORY_COUNT BYTECOUNT $files
gr LSTREAM_DATA_COUNT BYTECOUNT $files
gr ELEMENT_COUNT ELEMCOUNT $files
gr HASH_CODE HASHCODE $files
----------------------------------- cut ------------------------------------
`fixtypes.sh' is a Bourne-shell script; it uses 'gr':
----------------------------------- cut ------------------------------------
#!/bin/sh
# Usage is like this:
# gr FROM TO FILES ...
# globally replace FROM with TO in FILES. FROM and TO are regular expressions.
# backup files are stored in the `backup' directory.
from="$1"
to="$2"
shift 2
echo ${1+"$@"} | xargs global-replace "s/$from/$to/g"
----------------------------------- cut ------------------------------------
`gr' in turn uses a Perl script to do its real work,
`global-replace', which follows:
----------------------------------- cut ------------------------------------
: #-*- Perl -*-
### global-modify --- modify the contents of a file by a Perl expression
## Copyright (C) 1999 Martin Buchholz.
## Copyright (C) 2001 Ben Wing.
## Authors: Martin Buchholz <martin@xemacs.org>, Ben Wing <ben@xemacs.org>
## Maintainer: Ben Wing <ben@xemacs.org>
## Current Version: 1.0, May 5, 2001
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2, or (at your option)
# any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with XEmacs; see the file COPYING. If not, write to the Free
# Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
# 02111-1307, USA.
eval 'exec perl -w -S $0 ${1+"$@"}'
if 0;
use strict;
use FileHandle;
use Carp;
use Getopt::Long;
use File::Basename;
(my $myName = $0) =~ s@.*/@@; my $usage="
Usage: $myName [--help] [--backup-dir=DIR] [--line-mode] [--hunk-mode]
PERLEXPR FILE ...
Globally modify a file, either line by line or in one big hunk.
Typical usage is like this:
[with GNU print, GNU xargs: guaranteed to handle spaces, quotes, etc.
in file names]
find . -name '*.[ch]' -print0 | xargs -0 $0 's/\bCONST\b/const/g'\n
[with non-GNU print, xargs]
find . -name '*.[ch]' -print | xargs $0 's/\bCONST\b/const/g'\n
The file is read in, either line by line (with --line-mode specified)
or in one big hunk (with --hunk-mode specified; it's the default), and
the Perl expression is then evalled with \$_ set to the line or hunk of
text, including the terminating newline if there is one. It should
destructively modify the value there, storing the changed result in \$_.
Files in which any modifications are made are backed up to the directory
specified using --backup-dir, or to `backup' by default. To disable this,
use --backup-dir= with no argument.
Hunk mode is the default because it is MUCH MUCH faster than line-by-line.
Use line-by-line only when it matters, e.g. you want to do a replacement
only once per line (the default without the `g' argument). Conversely,
when using hunk mode, *ALWAYS* use `g'; otherwise, you will only make one
replacement in the entire file!
";
my %options = ();
$Getopt::Long::ignorecase = 0;
&GetOptions (
\%options,
'help', 'backup-dir=s', 'line-mode', 'hunk-mode',
);
die $usage if $options{"help"} or @ARGV <= 1;
my $code = shift;
die $usage if grep (-d || ! -w, @ARGV);
sub SafeOpen {
open ((my $fh = new FileHandle), $_[0]);
confess "Can't open $_[0]: $!" if ! defined $fh;
return $fh;
}
sub SafeClose {
close $_[0] or confess "Can't close $_[0]: $!";
}
sub FileContents {
my $fh = SafeOpen ("< $_[0]");
my $olddollarslash = $/;
local $/ = undef;
my $contents = <$fh>;
$/ = $olddollarslash;
return $contents;
}
sub WriteStringToFile {
my $fh = SafeOpen ("> $_[0]");
binmode $fh;
print $fh $_[1] or confess "$_[0]: $!\n";
SafeClose $fh;
}
foreach my $file (@ARGV) {
my $changed_p = 0;
my $new_contents = "";
if ($options{"line-mode"}) {
my $fh = SafeOpen $file;
while (<$fh>) {
my $save_line = $_;
eval $code;
$changed_p = 1 if $save_line ne $_;
$new_contents .= $_;
}
} else {
my $orig_contents = $_ = FileContents $file;
eval $code;
if ($_ ne $orig_contents) {
$changed_p = 1;
$new_contents = $_;
}
}
if ($changed_p) {
my $backdir = $options{"backup-dir"};
$backdir = "backup" if !defined ($backdir);
if ($backdir) {
my ($name, $path, $suffix) = fileparse ($file, "");
my $backfulldir = $path . $backdir;
my $backfile = "$backfulldir/$name";
mkdir $backfulldir, 0755 unless -d $backfulldir;
print "modifying $file (original saved in $backfile)\n";
rename $file, $backfile;
}
WriteStringToFile ($file, $new_contents);
}
}
----------------------------------- cut ------------------------------------
In addition to those programs, I needed to fix up a few other
things, particularly relating to the duplicate definitions of
types, now that some types merged with others. Specifically:
1. in lisp.h, removed duplicate declarations of Bytecount. The
changed code should now look like this: (In each code snippet
below, the first and last lines are the same as the original, as
are all lines outside of those lines. That allows you to locate
the section to be replaced, and replace the stuff in that
section, verifying that there isn't anything new added that
would need to be kept.)
--------------------------------- snip -------------------------------------
/* Counts of bytes or chars */
typedef EMACS_INT Bytecount;
typedef EMACS_INT Charcount;
/* Counts of elements */
typedef EMACS_INT Elemcount;
/* Hash codes */
typedef unsigned long Hashcode;
/* ------------------------ dynamic arrays ------------------- */
--------------------------------- snip -------------------------------------
2. in lstream.h, removed duplicate declaration of Bytecount.
Rewrote the comment about this type. The changed code should
now look like this:
--------------------------------- snip -------------------------------------
#endif
/* The have been some arguments over the what the type should be that
specifies a count of bytes in a data block to be written out or read in,
using Lstream_read(), Lstream_write(), and related functions.
Originally it was long, which worked fine; Martin "corrected" these to
size_t and ssize_t on the grounds that this is theoretically cleaner and
is in keeping with the C standards. Unfortunately, this practice is
horribly error-prone due to design flaws in the way that mixed
signed/unsigned arithmetic happens. In fact, by doing this change,
Martin introduced a subtle but fatal error that caused the operation of
sending large mail messages to the SMTP server under Windows to fail.
By putting all values back to be signed, avoiding any signed/unsigned
mixing, the bug immediately went away. The type then in use was
Lstream_Data_Count, so that it be reverted cleanly if a vote came to
that. Now it is Bytecount.
Some earlier comments about why the type must be signed: This MUST BE
SIGNED, since it also is used in functions that return the number of
bytes actually read to or written from in an operation, and these
functions can return -1 to signal error.
Note that the standard Unix read() and write() functions define the
count going in as a size_t, which is UNSIGNED, and the count going
out as an ssize_t, which is SIGNED. This is a horrible design
flaw. Not only is it highly likely to lead to logic errors when a
-1 gets interpreted as a large positive number, but operations are
bound to fail in all sorts of horrible ways when a number in the
upper-half of the size_t range is passed in -- this number is
unrepresentable as an ssize_t, so code that checks to see how many
bytes are actually written (which is mandatory if you are dealing
with certain types of devices) will get completely screwed up.
--ben
*/
typedef enum lstream_buffering
--------------------------------- snip -------------------------------------
3. in dumper.c, there are four places, all inside of switch()
statements, where XD_BYTECOUNT appears twice as a case tag. In
each case, the two case blocks contain identical code, and you
should *REMOVE THE SECOND* and leave the first.
author | ben |
---|---|
date | Thu, 20 Sep 2001 06:31:11 +0000 |
parents | 3ecd8885ac67 |
children |
line wrap: on
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STUDIES FIND REWARD OFTEN NO MOTIVATOR Creativity and intrinsic interest diminish if task is done for gain By Alfie Kohn Special to the Boston Globe [reprinted with permission of the author from the Monday 19 January 1987 Boston Globe] In the laboratory, rats get Rice Krispies. In the classroom the top students get A's, and in the factory or office the best workers get raises. It's an article of faith for most of us that rewards promote better performance. But a growing body of research suggests that this law is not nearly as ironclad as was once thought. Psychologists have been finding that rewards can lower performance levels, especially when the performance involves creativity. A related series of studies shows that intrinsic interest in a task - the sense that something is worth doing for its own sake - typically declines when someone is rewarded for doing it. If a reward - money, awards, praise, or winning a contest - comes to be seen as the reason one is engaging in an activity, that activity will be viewed as less enjoyable in its own right. With the exception of some behaviorists who doubt the very existence of intrinsic motivation, these conclusions are now widely accepted among psychologists. Taken together, they suggest we may unwittingly be squelching interest and discouraging innovation among workers, students and artists. The recognition that rewards can have counter-productive effects is based on a variety of studies, which have come up with such findings as these: Young children who are rewarded for drawing are less likely to draw on their own that are children who draw just for the fun of it. Teenagers offered rewards for playing word games enjoy the games less and do not do as well as those who play with no rewards. Employees who are praised for meeting a manager's expectations suffer a drop in motivation. Much of the research on creativity and motivation has been performed by Theresa Amabile, associate professor of psychology at Brandeis University. In a paper published early last year on her most recent study, she reported on experiments involving elementary school and college students. Both groups were asked to make "silly" collages. The young children were also asked to invent stories. The least-creative projects, as rated by several teachers, were done by those students who had contracted for rewards. "It may be that commissioned work will, in general, be less creative than work that is done out of pure interest," Amabile said. In 1985, Amabile asked 72 creative writers at Brandeis and at Boston University to write poetry. Some students then were given a list of extrinsic (external) reasons for writing, such as impressing teachers, making money and getting into graduate school, and were asked to think about their own writing with respect to these reasons. Others were given a list of intrinsic reasons: the enjoyment of playing with words, satisfaction from self-expression, and so forth. A third group was not given any list. All were then asked to do more writing. The results were clear. Students given the extrinsic reasons not only wrote less creatively than the others, as judged by 12 independent poets, but the quality of their work dropped significantly. Rewards, Amabile says, have this destructive effect primarily with creative tasks, including higher-level problem-solving. "The more complex the activity, the more it's hurt by extrinsic reward," she said. But other research shows that artists are by no means the only ones affected. In one study, girls in the fifth and sixth grades tutored younger children much less effectively if they were promised free movie tickets for teaching well. The study, by James Gabarino, now president of Chicago's Erikson Institute for Advanced Studies in Child Development, showed that tutors working for the reward took longer to communicate ideas, got frustrated more easily, and did a poorer job in the end than those who were not rewarded. Such findings call into question the widespread belief that money is an effective and even necessary way to motivate people. They also challenge the behaviorist assumption that any activity is more likely to occur if it is rewarded. Amabile says her research "definitely refutes the notion that creativity can be operantly conditioned." But Kenneth McGraw, associate professor of psychology at the University of Mississippi, cautions that this does not mean behaviorism itself has been invalidated. "The basic principles of reinforcement and rewards certainly work, but in a restricted context" - restricted, that is, to tasks that are not especially interesting. Researchers offer several explanations for their surprising findings about rewards and performance. First, rewards encourage people to focus narrowly on a task, to do it as quickly as possible and to take few risks. "If they feel that 'this is something I have to get through to get the prize,' they're going to be less creative," Amabile said. Second, people come to see themselves as being controlled by the reward. They feel less autonomous, and this may interfere with performance. "To the extent one's experience of being self-determined is limited," said Richard Ryan, associate psychology professor at the University of Rochester, "one's creativity will be reduced as well." Finally, extrinsic rewards can erode intrinsic interest. People who see themselves as working for money, approval or competitive success find their tasks less pleasurable, and therefore do not do them as well. The last explanation reflects 15 years of work by Ryan's mentor at the University of Rochester, Edward Deci. In 1971, Deci showed that "money may work to buy off one's intrinsic motivation for an activity" on a long-term basis. Ten years later, Deci and his colleagues demonstrated that trying to best others has the same effect. Students who competed to solve a puzzle quickly were less likely than those who were not competing to keep working at it once the experiment was over. Control plays role There is general agreement, however, that not all rewards have the same effect. Offering a flat fee for participating in an experiment - similar to an hourly wage in the workplace - usually does not reduce intrinsic motivation. It is only when the rewards are based on performing a given task or doing a good job at it - analogous to piece-rate payment and bonuses, respectively - that the problem develops. The key, then, lies in how a reward is experienced. If we come to view ourselves as working to get something, we will no longer find that activity worth doing in its own right. There is an old joke that nicely illustrates the principle. An elderly man, harassed by the taunts of neighborhood children, finally devises a scheme. He offered to pay each child a dollar if they would all return Tuesday and yell their insults again. They did so eagerly and received the money, but he told them he could only pay 25 cents on Wednesday. When they returned, insulted him again and collected their quarters, he informed them that Thursday's rate would be just a penny. "Forget it," they said - and never taunted him again. Means to and end In a 1982 study, Stanford psychologist Mark L. Lepper showed that any task, no matter how enjoyable it once seemed, would be devalued if it were presented as a means rather than an end. He told a group of preschoolers they could not engage in one activity they liked until they first took part in another. Although they had enjoyed both activities equally, the children came to dislike the task that was a prerequisite for the other. It should not be surprising that when verbal feedback is experienced as controlling, the effect on motivation can be similar to that of payment. In a study of corporate employees, Ryan found that those who were told, "Good, you're doing as you /should/" were "significantly less intrinsically motivated than those who received feedback informationally." There's a difference, Ryan says, between saying, "I'm giving you this reward because I recognize the value of your work" and "You're getting this reward because you've lived up to my standards." A different but related set of problems exists in the case of creativity. Artists must make a living, of course, but Amabile emphasizes that "the negative impact on creativity of working for rewards can be minimized" by playing down the significance of these rewards and trying not to use them in a controlling way. Creative work, the research suggests, cannot be forced, but only allowed to happen. /Alfie Kohn, a Cambridge, MA writer, is the author of "No Contest: The Case Against Competition," recently published by Houghton Mifflin Co., Boston, MA. ISBN 0-395-39387-6. /