A language declaration must be enclosed thus:

Language "NAME" {
	...
}

where the body ... consists of blank lines, or of any of the following, given in any order:

Conventions used in language declarations

In addition, a language declaration (like any Inweb resource declaration) can finish up by including a Conventions block. Only the following conventions are really appropriate for a language, though:

named holons are tangled between BEFORE and AFTER
standard library #includes are tangled early in the program
typedefs are tangled early in the program
typedef structs are tangled early and reordered logically
function predeclarations are tangled automatically

The last four are relevant only for C and variants of C: see Special C Features. The first, though, can be useful in making the holons for a language behave like code blocks: see Holons as Code Blocks for why we might want this. For example, Inweb's definition of C contains:

named holons are tangled between <NEWLINE>{<NEWLINE> and }<NEWLINE>

which means that when a named holon is expanded in tangling, it's encased in C's open and close block syntax, { ... }. The newlines are not entirely cosmetic — we want to ensure that any subsequent #line directive will appear at the start of a line. By default:

named holons are tangled between <NEWLINE> and <NEWLINE>

Many languages which are not strictly speaking versions of C also brace their code blocks: so, for example, the definition of Rust in Creating Languages made the same convention.

The properties block

Everything else having now been fully specified, it remains to give an exhaustive list of the settings which can be made in the properties block.

Properties can be textual (as the great majority are), boolean (in which case they must be true or false), or regexp, that is, they hold a regular expression. Here are examples of each being set:

properties
	Character Literal:		'
	C-Like: 				false
	Function Declaration:	/def ([A-Za-z_][A-Za-z0-9_]*).*/
end

Textual properties can either be quoted or not. If quoted, they should be in double-quotes: "Thus". Within those, \" means a double quotation mark, \n means a newline, and \\ means a backslash. If unquoted, they are taken just as they are, with no special characters (and thus cannot contain newlines).

A textual value is read as quoted if it contains at least two characters, and the first and last are quotation marks: thus " is unquoted, and means a single-character text where the character in question is a double-quotation mark; but "" is quoted and means the empty text.

By default, the following properties are all empty or false if not set.

Details: textual. A one-line note explaining the purpose of this "language", used only in the output of inweb inspect -show-resources. Style note: for consistency, start with a capital letter, but finish without a full stop. Example:

Details: The C++ programming language

Line Comment: textual. The characters introducing a comment which continues to the end of the line, but which can appear in any (unquoted, uncommented-out) position. Affects tangling as well as weaving since Inweb will not expand holon names when they are commented out. Example:

Line Comment: //

Whole Line Comment: textual. Like Line Comment, but allowed only at the start of a line, where "start" means that these are the first non-whitespace characters on that line. Example:

Line Comment: #

Multiline Comment Open: textual. The characters introducing a comment which continues to the next use of Multiline Comment Close (so, these should either both be defined, or neither). This form of comment can begin and end in any (unquoted, uncommented-out) position and can, but need not, spread across multiple lines. Affects tangling as well as weaving since Inweb will not expand holon names when they are commented out. Example:

Multiline Comment Open: {-
Multiline Comment Close: -}

Multiline Comment Open: textual. See Multiline Comment Open.

String Literal: textual. The characters opening and also closing a string literal. Affects tangling as well as weaving since Inweb will not expand holon names when they appear only in string literals. Example:

String Literal: "

String Literal Escape: textual. If used inside a string literal, means that any use of String Literal immediately following should not be counted as its end. Example:

String Literal Escape: \

Character Literal: textual. Like String Literal, but for character literals. Example:

Character Literal: '

Character Literal Escape: textual. Like String Literal Escape, but for character literals. Example:

Character Literal Escape: \

Binary Literal Prefix: textual. Introduces a binary number literal, which then must continue with digits which are each 0 or 1. Affects only syntax-colouring. Example:

Binary Literal Prefix: 0b

Octal Literal Prefix: textual. Introduces a binary number literal, which then must continue with digits which are each 0, 1, 2, 3, 4, 5, 6, 7. Affects only syntax-colouring. Example:

Binary Literal Prefix: 0o

Hexadecimal Literal Prefix: textual. Introduces a binary number literal, which then must continue with digits which are each 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, a or A, b or B, c or C, d or D, e or E, f or F. Affects only syntax-colouring. Example:

Hexadecimal Literal Prefix: 0x

Negative Literal Prefix: textual. Introduces a decimal number literal which is negative. Affects only syntax-colouring. Example (and it's hard to imagine any other value being set here):

Negative Literal Prefix: -

Decimal Point Infix: textual. Used inside a decimal number literal, acts as a decimal point. Affects only syntax-colouring. Example (and it's hard to imagine any other value being set here):

Decimal Point Infix: .

Exponent Infix: textual. Used inside a decimal number literal, acts as an exponent marker. Affects only syntax-colouring. Example:

Exponent Infix: e

Shebang: textual. Affects only tangling. Place this text at the very top of any tangled program, followed by a newline. The name goes back to the old Unix scripting tools, whose input conventionally opened with a comment saying what program (usually a compiler or interpreter) should run them. Example:

Shebang: "#!/usr/bin/perl\n\n"

Line Marker: textual. Affects only tangling. Placed every time the tangler draws source material from different files or line numbers than the compiler might be expecting. %d should be placed where the line number is to go, and %f where the filename should be. Example:

Line Marker: "#line %d \"%f\"\n"

Indent Named Holon Expansion: boolean. If true, holon expansion should respect the current indentation level. This needs to be set for Pythonesque languages: see Holons as Code Blocks. Example:

Indent Named Holon Expansion: true

Start Definition: textual. If defining a symbol through an explicit notation in the web source (for example using @d in InwebClassic), Inweb tangles this at the opening of a definition. Example (from C):

Start Definition: "#define %S "

Prolong Definition: textual. If the value of a definition continues across a second or still further lines, then this text is tangled in between those lines. Example (from C):

Prolong Definition: "\\\n    "

End Definition: textual. Tangled at the end of the value from a definition begun with Start Definition. Example (from C):

End Definition: "\n"

Start Ifdef: textual. When tangling code which should be compiled only if a given symbol is defined, Inweb expands this string, in which %S is expanded as the symbol. No other % escapes should be used. Example (from Inform 6):

Start Ifdef: "#ifdef %S;\n"

Start Ifndef: textual. Similarly for conditional compilation if a symbol is not defined. Example (from Inform 6):

Start Ifdef: "#ifndef %S;\n"

End Ifdef: textual. Inweb tangles this at the end of a passage of code prefaced with Start Ifdef: so both should be defined, or neither. Once again %S expands into the symbol name (though this may not be needed, or might only be used in a comment). Example (from Inform 6):

End Ifdef: "#endif; ! %S\n"

End Ifndef: textual. Similarly to End Ifdef, but for passages which began with Start Ifndef.

C-Like: boolean. If true, this language gains certain Inweb features reserved for variants of C. See Special C Features. Example:

C-Like: true

Supports Namespaces: boolean. This is intended only for C-like languages, and provides some semblance of a namespace feature for function names (though not for other identifiers). See Special C Features. Example:

Supports Namespaces: true

Function Declaration: regexp. If set, Inweb attempts to parse (non-comment) lines against this regular expression: if there's a match, then the first bracketed subexpression is assumed to be the name of a new function declared on that line, and is made a keyword of colour !function. Multiple expressions can be made alternatives by writing multiple Function Declaration lines. See Recognising Functions and Types. Example:

Function Declaration: /fn (\S+?)\s*\(.*/

Type Declaration: regexp. Similar to Function Declaration, but for the colour !type. Again, see Recognising Functions and Types. Example:

Type Declaration: /typedef struct (\S+).*/
Type Declaration: /typedef .* (\S+);\s*/