README.markdown

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.

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 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