C-- has a type. This section documents
the data types in C--. You can produce values of the simpler
data types (integers, strings, dbrefs, symbols, error codes) can be
produced with literal expressions; you can produce values of the
more complex data types (lists, dictionaries, frobs, buffers) with
constructor expressions. As we go, we will explain how to specify
or construct values of each of the data types, and explain what it means
for a value of each data type to be true.
Every piece of data in C-- has a type and a truth value. The
type can be one of:
C-- by writing a sequence of
digits, optionally preceded by a - or + sign.
A string is a sequence of printable characters. A string is true
if it is not empty. You can denote string literals in C-- by
enclosing a sequence of characters in double quotes ("). To
include a double quote or backslash character in a string literal,
precede it by a backslash (\). The following are string
literals:
"foo" "\"foo\" is a metasyntactic variable." "The backslash (`\\') is a much-abused character in many languages."A dbref is a reference to an object, which may or may not exist. Database references are always true, whether or not they refer to actual objects. You can denote dbref literals in
C-- by preceding a
number with a sharp (#); for example, #1 and #267
are valid dbref literals.
A list is a collection of objects of any type. Lists are useful
for manipulating several objects at once. A list is true if it is not
empty. You can construct a list value by enclosing a comma-separated
series of expressions in square brackets; for example, [1, 2, 3]
and [1, ["foo", 'bar], #23] are valid list construction
expressions.
A symbol is a symbolic value. You can denote symbols in
C-- by preceding an identifier or string with an apostrophe
('). 'remote, 'template, and 'object are
valid symbol literals. Symbols are always true.
An error code identifies a type of error condition. Both the
C-- interpreter and C-- methods use error codes to
identify types of errors when they occur. See Errors for
information about how Coldmud handles errors. You can denote error code
literals in C-- by preceding an identifier or string with a tilde
(~). Error codes are always false.
A frob consists of a class, the dbref of an object, and a
representation, a list or dictionary. Frobs are intended to
serve as lightweight objects. You can construct a frob value by
enclosing expressions for the class and representation in triangular
brackets, separated by a comma; for instance, <#73, [1, 2]> is a
valid frob construction expression. Frobs are always true.
A dictionary is a collection of associations, each of
which has a key and a value. Dictionaries take up more
space than lists, but searching for a data value in a dictionary is
generally faster than searching for data values in lists. You can
construct a dictionary by enclosing a comma-separated series of
associations in square brackets, where each association is a two-element
list giving a key and a value, and preceding the whole thing with a hash
mark (#). For instance, #[["foo", 3], ["bar", 'baz]] is a
valid dictionary construction expression. A dictionary is true if it is
not empty.
a buffer is an array of unsigned eight-bit values, intended for
network I/O. You can construct a buffer by enclosing a comma-separated
series of integer expressions in square brackets, preceded by a percent
sign (%). For instance, %[65, 66, 67, 10] is a valid
buffer construction expression. A buffer is true if it is not empty.
You can get the type of a piece of C-- data using the
type() function. The type() function returns a symbol
corresponding to the type of its argument. This symbol can be
'integer, 'string, 'dbref, 'list,
'symbol, 'error, 'frob, or 'dictionary.