Sigil for Variable Names

new crotchet: all function parameter names should start with φ and all local variable names should start with ξ .

Example in JavaScript:

function draw_rect (φx_coord, φy_coord, φwidth, φheight) {
    // returns a svg rect element
    var rect = document.createElementNS("http://www.w3.org/2000/svg", "rect");
    rect.setAttribute("x", φx_coord.toString());
    rect.setAttribute("y", φy_coord.toString());
    rect.setAttribute("width", φwidth.toString());
    rect.setAttribute("height", φheight.toString());
    return rect;
}

〔see JavaScript Tutorial by Example〕

this is experimental. I'm going to see how it goes.

note, the choice of the character takes some consideration. You want a char that is:

• Unicode letter. (such as Greek letter), because some languages do not allow identifier to start with a char that's not a Unicode letter. (For example, Python 2. Lexical analysis — Python v3.3.3 documentation#identifiers and JavaScript. For what's a Unicode letter, see: JS: Allowed Characters in Identifier)
• Widely recognized. (For example, Chinese char would not be appropriate.)
• Visually distinct from English alphabets, regardless of font.
• Lower case and upper case can be distinguished, and also both must be visually distinct from any lower case or upper case English alphabets. (For example, greek ε and its capital Ε would be bad.)

note: sigil is mostly popularly associated with perl. But it's also used in PHP and Ruby, as these 2 languages directly borrowed it from Perl. (perl borrowed it from unix shell.) 〔see Perl Tutorial〕 〔see PHP in 1 Hour〕 〔see Ruby Tutorial〕

The idea of sigil is however quite widespread. Many languages have special chars as starting or ending variable names to indicate special purpose, though, mostly as a convention only, not part of the language machinery.

For example:

• Python class names always start with CapitalLetter. This is by convention.
• OCaml variable must start with lower case.
• In many languages, by convention, variable start with _ means it's not used.
• In many languages, by convention, variable start with double _ means it's internal.
• Mathematica builtin names start with Capital case.
• Mathematica variables starting with $ are predefined global special variables. (see: http://reference.wolfram.com/mathematica/tutorial/GlobalSystemInformation.html), since 1988.

the name sigil is coined by Philip Gwyn in 1999 to refer to perl's sigil, according to Wikipedia.