The Cfluviurrh Programming Language
===================================
Version 1.0
_Cfluviurrh_ is, as far as I am aware, the first programming language designed
for writing programs that can *feel*. Cfluviurrh defines a mechanism by which
a program can be instructed to experience particular emotions.
You might, thus, on first blush, consider Cfluviurrh to be unimplementable,
as modern-day computers are not capable of experiencing emotions (you guess.)
However, this is demonstrably untrue. There is nothing that strictly requires
a computer program to be executed entirely on an electronic computer. It is
simply that, to be correctly implemented, Cfluviurrh must be implemented for a
system that we know is, in some way, capable of experiencing emotions.
For example, it could be implemented as a contractual obligation for a
[method actor][], or similar professional capable of feeling emotions on
demand; this individual would be required to read a program text written in
Cfluviurrh, and carry out its instructions, feeling the specified emotions
at the required points in the program.
Or, in the approach the reference implementation takes, an electronic
computer may co-operate with a contractually obligated individual termed
the "emoter". The computer executes all the parts of the program which do
not necessitate emotional experience, and prompts the emoter to experience
emotions on behalf of the running program when required.
[method actor]: http://en.wikipedia.org/wiki/Method_acting
Design
------
### Program State ###
The state of a running Cfluviurrh program consists of an unlimited number of
registers, each of which can contain a non-negative integer of unlimited
size. (Of course, a particular implementation may impose its own limits
here, as we can't expect computers to be infinite [I guess.])
The registers are indexed by number, starting at zero; the first twenty-six
(registers 0 to 25) also have names, `a` through `z`. Initially, every
register contains a zero value.
There is also a special value called the _instruction pointer_ (IP), which
indicates which character in the Cfluviurrh program will be executed next.
As statements are executed, the IP is advanced to the next statement in the
program text (except in the case of a jump, described below.) The IP
initially refers to the first character of the program.
There is also a special value called the _emotion bank number_, which is
initially zero. An implementation must implement emotion bank zero,
but need not implement any other emotion banks, nor need it implement
emotion bank switching. All emotion banks other than zero are undefined
and reserved for future use.
### Syntax ###
A Cfluviurrh program text is a sequence of ASCII characters. In the course
of execution, the character at the IP is considered to be the start of the
next statement.
A statement is either:
* _whitespace_ (a space, tab, newline, or carriage feed character);
nothing happens when this is executed, the IP is simply advanced
to the next character.
* a _comment_, which begins with `(`; the IP is advanced to one
character past the next `)` character in the program, with nothing
else happening. Comments do not nest.
* a _label_, which is a `:` followed by any printable character
(called the _label name_). The IP is advanced to one character past
the label name; nothing else happens.
* a _register reference_, followed by an operator. A register reference
is a lowercase letter from `a` to `z`, which refers to the register
with the same name, *or* an uppercase letter from `A` to `Z`, which
refers to the register with the index given by the contents of the
register with the corresponding lower-case name. (So if register `a`
contained the number 4, `A` would refer to register `e`.)
There are several subcases for the syntax of a statement which begins
with a register reference. These are:
* an _assignment_, which is where the register reference is followed
by a `=` character, which is followed by a value. A value can
be either a register reference, in which case the value is taken
from the register being referred to, or it may be a literal
digit from `0` to `9`, in which case it is the value of that
digit as an Arabic numeral. Thus, `a=1`, `b=B`, and `R=4` are
all valid assignment statements, but `7=a` is not.
* a _modifying assignment_, which is where the register reference is
followed by one of the characters `+`, `-`, `*`, or `/`, which is
followed by a `=` character which is followed by a value. The
register being referred to has the value added to it, subtracted
from it, is multiplied by the value, or is divided (integer
division, rounding down) by the value, respectively, based on the
operator character. Thus, `a+=1`, `a*=2`, and `F/=f` are all
valid modifying assignments.
* a _label location assignment_, which is where the register reference
is followed by a `@` character which is followed by a `=` character
which is followed by a label name. A label with this label name
is sought in the program and, if found, the position of the label
in the program text (with 0 being the position of the first character
of the program, and with all characters, including whitespace and
comments, having sequential positions within the program) is written to
the register. If there are multiple labels with the same label name,
the one closest to the start of the program text is chosen. If a
matching label is not found, "an error occurs", whatever that means
exactly.
* an _output statement_, which is where the register reference
is followed by a `>` character. The ASCII character with the same
value as the contents of the register will be written to the program's
output stream. If the value of the register is outside of the range
0 to 127, "an error occurs".
* an _input statement_, which is where the register reference
is followed by a `<` character. An ASCII character is retrieved from
the program's input stream, and its value is written into the register.
* a _jump statement_, which is where the register reference is followed
by a `?` character, followed by a _conditional_. A conditional is a
value, followed by one of the characters `=`, `>`, or `<`, followed by
a value. A conditional, when evaluated during a program run, is either
true or false. A conditional has the meaning you would probably
expect; `2=2` is true, `4>5` is false, and `A<2` is true if the `a`
register contains 4 and the `e` register contains 1. If the
conditional is true, the IP is set to the value found in the register
referred to by the register reference; otherwise, the IP advances
as usual. Either way, an emotion is experienced (see below) every
time a jump statement is executed.
* an _emotion bank switch statement_, which is where the register
reference is followed by a `=` followed by a `>`. The emotion bank
is switched to the value in the register. The previous emotion bank
number is then written to the register for posterity. If that emotion
bank is not supported by the implementation, "an error occurs". An
"error" may also "occur" if emotion bank switching is not supported
by the implementation.
Note that whitespace and comments are not allowed inside any statement
which begins with a register reference. If an attempt is made to execute any
statement which does not conform to the above syntax, "an error occurs".
The input stream and output stream are implementation-defined concepts.
If division by zero is attempted, "an error occurs".
If a jump is made to a position beyond the extent of the program text, either
the program just ends, or "an error occurs" -- implementor's choice.
### Experiencing Emotions ###
Whenever a jump statement is executed, an emotion is experienced at a certain
intensity level.
The emotion being experienced, and the intensity level, depends on the
currently active emotion bank. Only emotion bank zero is described here.
The contents of the first twenty-six registers, at the point in time that
the emotion is to be experienced, are summed (modulo 74) to obtain an
_emotion number_. The emotion number refers to the following table; it
is consulted to obtain the emotion to be experienced.
* 0: sadness
* 1: sorrow
* 2: despair
* 3: worry
* 4: depression
* 5: misery
* 6: melancholy
* 7: wistfulness
* 8: disappointment
* 9: regret
* 10: longing
* 11: impatience
* 12: anger
* 13: hostility
* 14: rage
* 15: hatred
* 16: disgust
* 17: contempt
* 18: envy
* 19: arrogance
* 20: betrayal
* 21: hurt
* 22: grief
* 23: remorse
* 24: shame
* 25: embarrassment
* 26: guilt
* 27: timidity
* 28: loneliness
* 29: annoyance
* 30: frustration
* 31: confusion
* 32: shock
* 33: angst
* 34: anguish
* 35: anxiety
* 36: apathy
* 37: vindication
* 38: gratitude
* 39: hope
* 40: awe
* 41: wonder
* 42: surprise
* 43: pity
* 44: boredom
* 45: apprehension
* 46: distrust
* 47: dread
* 48: horror
* 49: loathing
* 50: terror
* 51: panic
* 52: hysteria
* 53: pride
* 54: anticipation
* 55: curiosity
* 56: boldness
* 57: excitement
* 58: thrill
* 59: zeal
* 60: enthusiasm
* 61: calmness
* 62: contentment
* 63: satisfaction
* 64: happiness
* 65: bliss
* 66: joy
* 67: ecstasy
* 68: euphoria
* 69: admiration
* 70: desire
* 71: passion
* 72: love
* 73: lust
There are five intensity levels, listed in the following table. To find the
intensity level of an emotion to be experienced, each of the first twenty-six
registers are multiplied by three (modulo five) and this set of values is
summed (modulo five.)
* 0: faint
* 1: mild
* 2: moderate
* 3: marked
* 4: extreme
Implementation
--------------
The reference implementation of Cfluviurrh is an interpreter written in
ANSI C, and imposes arbitrary limits on the size of the program text, the
number of registers, and the maximum value of each integer in a register
(by default, 8000 characters, 8000 registers, and whatever `int` means to
your C compiler, respectively); however, these arbitrary limits should not
be taken as defining limitations on the language's execution model. It's
just that, you know, it's C.
As mentioned, the reference implementation requires the user to agree to
act as the emoter. As it uses C's standard input and standard output to
interact with the emoter, asking them to agree to act as the emoter, and
prompting them to feel the required emotions, the input stream and output
stream of the Cfluviurrh program are assigned to two files given on the
command line:
cfluviurrh <program-file> <input-file> <output-file>
To facilitate interactive Cfluviurrh programs, the input-file and
output-file may be named pipes, or (on AmigaOS) console devices, or
something.
When "an error occurs" the reference interpreter generally exits to the
operating system with an error message of some sort. Although, it may
just crash, too.
Discussion
----------
The name "Cfluviurrh" is a kind of irrational portmanteau of *catarrh*
and *effluvium*. I hope I'm never asked to present on it at a conference,
because I'm not quite sure how to pronounce it.
The idea to design a programming language which supports the experiencing of
emotions came to me in the summer of 2011 while I was in Toronto's Pearson
International Airport. (Let the critics who insist that YYZ has contributed
[nothing](http://en.wikipedia.org/wiki/YYZ_%28song%29) to culture be
silenced!)
It then dovetailed, about a year later, with an urge I had to design a
language with a fairly intuitive syntax, but simple enough that writing a
"real" parser would not be necessary. I implemented it in C partly because it
would be nice to port it to AmigaOS 1.3 someday, and partly because, if I
don't have enough C repos on Github to outnumber my legacy Perl repos,
they'll label Cat's Eye Technologies a Perl outfit, and I don't particularly
want that.
One of the design challenges (though not, I should not, a very difficult one)
was making it so that every non-trivial Cfluviurrh program experienced *some*
emotion. Tying it to the conditional jump statement solved that problem.
The upshot is that "Hello, world!" feels nothing at all, while "99 bottles"
or printing out the ASCII table goes through a bewildering array of emotions.
While some of the entries in the emotion table may not be emotions per se,
and while some combinations of intensity and emotion, such as "faint zeal",
"mild rage", and "extreme apathy" may be tricky to express, this does not
detract from the bare fact that Cfluviurrh *does* support experiencing
emotions.
Cfluviurrh is Turing-complete. Proof of this is left as an exercise for the
reader (don't you hate it when authors say that?)
Because every label name can only be a single printable character, it might
appear that the number of jump destinations in a program is limited to 95.
This is not true, as labels are only a convenience. You can load any value
you like into a register, then jump to that position in the program text.
In fact, there is nothing stopping you from jumping inside a comment, with
a label or otherwise. In fact, from this perspective, comments could be
somewhat valuable control flow structures; consider
... (:A ... (:B ... () ...
Execution coming in from the left will skip this "block"; execution coming
in at the `:A` label will skip the "inner block", and execution coming in
at `:B` will only execute the "inner block".
Happy Cfluviurrhing! (Or sad Cfluviurrhing, or timid Cfluviurrhing, or...)
Chris Pressey
Winnipeg, Manitoba
August 26, 2012