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Edit some documentation of unions and macros

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Rangi42
2024-08-22 00:41:07 -04:00
parent b438c83bda
commit 7bc9a24bf0
1 changed files with 40 additions and 28 deletions
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66
man/rgbasm.5
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@@ -1688,39 +1688,50 @@ keyword.
.Ic NEXTU .Ic NEXTU
separates each block of allocations, and you may use it as many times within a union as necessary. separates each block of allocations, and you may use it as many times within a union as necessary.
.Bd -literal -offset indent .Bd -literal -offset indent
; Let's say PC = $C0DE here ; Let's say PC == $C0DE here
UNION UNION
; Here, PC = $C0DE ; Here, PC == $C0DE
Name: ds 8 wName:: ds 10
; PC = $C0E6 ; Now, PC == $C0E8
Nickname: ds 8 wNickname:: ds 10
; PC = $C0EE ; PC == $C0F2
NEXTU NEXTU
; PC is back to $C0DE ; PC is back to $C0DE
Health: dw wHealth:: dw
; PC = $C0E0 ; PC == $C0E0
Something: ds 6 wLives:: db
; And so on ; PC == $C0E1
Lives: db ds 7
NEXTU ; PC == $C0E8
VideoBuffer: ds 19 wBonus:: db
ENDU ; PC == $C0E9
NEXTU
; PC is back to $C0DE again
wVideoBuffer: ds 16
; PC == $C0EE
ENDU
; Afterward, PC == $C0F2
.Ed .Ed
.Pp .Pp
In the example above, In the example above,
.Sq Name , Health , VideoBuffer .Sq wName , wHealth ,
all have the same value, as do
.Sq Nickname
and and
.Sq Lives . .Sq wVideoBuffer
all have the same value; so do
.Sq wNickname
and
.Sq wBonus .
Thus, keep in mind that Thus, keep in mind that
.Ql ld [Health], a .Ql ld [wHealth], a
is identical to assembles to the exact same thing as
.Ql ld [Name], a . .Ql ld [wName], a .
.Pp .Pp
The size of this union is 19 bytes, as this is the size of the largest block (the last one, containing This whole union's total size is 20 bytes, the size of the largest block (the first one, containing
.Sq VideoBuffer ) . .Sq wName
Nesting unions is possible, with each inner union's size being considered as described above. and
.Sq wNickname ) .
.Pp
Unions may be nested, with each inner union's size being determined as above, and affecting its outer union like any other allocation.
.Pp .Pp
Unions may be used in any section, but they may only contain space-allocating directives like Unions may be used in any section, but they may only contain space-allocating directives like
.Ic DS .Ic DS
@@ -1728,12 +1739,13 @@ Unions may be used in any section, but they may only contain space-allocating di
.Sx Statically allocating space in RAM ) . .Sx Statically allocating space in RAM ) .
.Sh THE MACRO LANGUAGE .Sh THE MACRO LANGUAGE
.Ss Invoking macros .Ss Invoking macros
You execute the macro by inserting its name. A macro is invoked by writing its name at the beginning of a line, followed by any arguments.
.Bd -literal -offset indent .Bd -literal -offset indent
add a, b add a, b
ld sp, hl ld sp, hl
MyMacro ;\ This will be expanded MyMacro ;\ This will be expanded
sub a, 87 sub a, 87
MyMacro 42 ;\ So will this
.Ed .Ed
.Pp .Pp
It's valid to call a macro from a macro (yes, even the same one). It's valid to call a macro from a macro (yes, even the same one).