5.5 KiB
Syntax
For information about types, see Types.
For information about literals, see Literals.
For information about assembly, see Using assembly within Millfork programs.
Comments
Comments start with //
and last until the end of line.
Declarations
Variable declarations
A variable declaration can happen at either top level of a file (global variables), or a top level of a function (local variables).
Syntax:
[segment(<segment>)] [<storage>] <type> <name> [@<address>] [= <initial_value>]
-
<segment>
: segment name; if absent, then defaults todefault
. -
<storage>
can be only specified for local variables. It can be eitherstack
,static
,register
or nothing.register
is only a hint for the optimizer. See the description of variable storage. -
<address>
is a constant expression that defines where in the memory the variable will be located. If not specified, it will be located according to the usual allocation rules.stack
variables cannot have a defined address. -
<initial_value>
is a constant expression that contains the initial value of the variable. Only global variables can be initialized that way. The behaviour is undefined when targeting a ROM-based platform.
Constant declarations
const <type> <name> = <value>
TODO
Array declarations
An array is a continuous sequence of bytes in memory.
Syntax:
[segment(<segment>)] array <name> [[<size>]] [@<address>] [= <initial_values>]
<segment>
: segment name; if absent, then defaults todefault_code_segment
as defined for the platform if the array has initial values, or todefault
if it doesn't.
TODO
Function declarations
A function can be declared at the top level. For more details, see Functions
import
statements
TODO
Statements
Expression statement
TODO
if
statement
Syntax:
if <expression> {
<body>
}
if <expression> {
<body>
} else {
<body>
}
return
statement
Syntax:
return
return <expression>
return[]
statement (return dispatch)
Syntax examples:
return [a + b] {
0 @ underflow
255 @ overflow
default @ nothing
}
return [getF()] {
1 @ function1
2 @ function2
default(5) @ functionDefault
}
return [i] (param1, param2) {
1,5,8 @ function1(4, 6)
2 @ function2(9)
default(0,20) @ functionDefault
}
Return dispatch calculates the value of an index, picks the correct branch, assigns some global variables and jumps to another function.
The index has to evaluate to a byte. The functions cannot be macro
and shouldn't have parameters.
Jumping to a function with parameters gives those parameters undefined values.
The functions are not called, so they don't return to the function the return dispatch statement is in, but to its caller.
The return values are passed along. If the dispatching function has a non-void
return type different that the type
of the function dispatched to, the return value is undefined.
If the default
branch exists, then it is used for every missing index value between other supported values.
Optional parameters to default
specify the maximum, or both the minimum and maximum supported index value.
In the above examples: the first example supports values 0–255, second 1–5, and third 0–20.
If the index has an unsupported value, the behaviour is formally undefined, but in practice the program will simply crash.
Before jumping to the function, the chosen global variables will be assigned parameter values. Variables have to be global byte-sized. Some simple array indexing expressions are also allowed. Parameter values have to be constants. For example, in the third example one of the following will happen:
-
if
i
is 1, 5 or 8, thenparam1
is assigned 4,param2
is assigned 6 and thenfunction1
is called; -
if
i
is 2, thenparam1
is assigned 9,param2
is assigned an undefined value and thenfunction2
is called; -
if
i
is any other value from 0 to 20, thenparam1
andparam2
are assigned undefined values and thenfunctionDefault
is called; -
if
i
has any other value, then undefined behaviour.
while
and do-while
statements
Syntax:
while <expression> {
<body>
}
do {
<body>
} while <expression>
for
statements
Warning: for
loops are a bit buggy.
Syntax:
for <variable>,<start>,<direction>,<end> {
}
-
<variable>
– an already defined numeric variable -
<direction>
– the range to traverse:-
to
– from<start>
inclusive to<end>
inclusive, in ascending order (e.g.0,to,9
to traverse 0, 1,... 9) -
downto
– from<start>
inclusive to<end>
inclusive, in descending order (e.g.9,downto,0
to traverse 9, 8,... 0) -
until
– from<start>
inclusive to<end>
exclusive, in ascending order (e.g.0,until,10
to traverse 0, 1,... 9) -
parallelto
– the same asto
, but the iterations may be executed in any order -
paralleluntil
– the same asuntil
, but the iterations may be executed in any order
There is no
paralleldownto
, because it would do the same asparallelto
. -
break
and continue
statements
Syntax:
break
break for
break while
break do
break <variable>
continue
continue for
continue while
continue do
continue <variable>