Propeller Manual

CON – Spin Language Reference
Page 84 · Propeller Manual v1.1
CON
Designator: Declare a Constant Block.
CON
Symbol = Expression 〈(( ,┆  )) Symbol = Expression〉…
CON
#Expression (( ,┆  )) Symbol 〈[Offset]〉 〈(( ,┆  )) Symbol 〈[Offset]〉 〉…
CON
Symbol 〈[Offset]〉 〈(( ,┆  )) Symbol 〈[Offset]〉 〉…
•
Symbol is the desired name for the constant.
•
Expression is any valid integer, or floating-point, constant algebraic expression.
Expression can include other constant symbols as long as they were defined
previously.
•
Offset is an optional expression by which to adjust the enumeration value for the
Symbol following this one. If Offset is not specified, the default offset of 1 is applied.
Use Offset to influence the next Symbol’s enumerated value to something other than
this Symbol’s value plus 1.
Explanation
The Constant Block is a section of source code that declares global constant symbols and
global Propeller configuration settings. This is one of six special declarations (
CON, VAR, OBJ,
PUB, PRI, and DAT) that provide inherent structure to the Spin language. T
Constants are numerical values that cannot change during run time. They can be defined in
terms of single values (1, $F, 65000, %1010, %%2310, “A”, etc.) or as expressions, called
constant expressions, (25 + 16 / 2, 1000 * 5, etc.) that always resolve to a specific number.
The Constant Block is an area of code specifically used for assigning symbols (useful names)
to constants so that the symbols can be used anywhere in code where that constant value is
needed. This makes code more readable and easier to maintain should you later have to
change the value of a constant that appears in many places. These constants are global to the
object so that any method within it can use them. There are many ways to define constants,
described below.