mirror of
https://github.com/ganelson/inform.git
synced 2024-07-18 06:54:26 +03:00
51 lines
1.9 KiB
OpenEdge ABL
51 lines
1.9 KiB
OpenEdge ABL
[NopInstruction::] The Nop Construct.
|
|
|
|
Defining the nop construct.
|
|
|
|
@h Definition.
|
|
This instruction does nothing at all, has no textual representation and is
|
|
nevertheless useful when constructing Inter in memory.
|
|
|
|
It exists as a convenience used by Inform when it needs to write simultaneously to
|
|
multiple positions within the same node's child list -- the idea being that
|
|
a nop statement acts as a divider. For example, by placing the A write
|
|
position just before a nop N, and the B write position just after, Inform
|
|
will generate A1, A2, A3, ..., N, B1, B2, ..., rather than (say) A1, B1, A2,
|
|
A3, B2, ... The extra N is simply ignored in code generation, so it causes
|
|
no problems to have it.
|
|
|
|
=
|
|
void NopInstruction::define_construct(void) {
|
|
inter_construct *IC = InterInstruction::create_construct(NOP_IST, I"nop");
|
|
InterInstruction::data_extent_always(IC, 0);
|
|
InterInstruction::allow_in_depth_range(IC, 0, INFINITELY_DEEP);
|
|
InterInstruction::permit(IC, OUTSIDE_OF_PACKAGES_ICUP);
|
|
InterInstruction::permit(IC, INSIDE_PLAIN_PACKAGE_ICUP);
|
|
InterInstruction::permit(IC, INSIDE_CODE_PACKAGE_ICUP);
|
|
METHOD_ADD(IC, CONSTRUCT_WRITE_MTID, NopInstruction::write);
|
|
}
|
|
|
|
@h Instructions.
|
|
In bytecode, the frame of a |nop| instruction consists only of the two
|
|
compulsory words -- see //Inter Nodes//.
|
|
|
|
=
|
|
inter_error_message *NopInstruction::new(inter_bookmark *IBM, inter_ti level,
|
|
inter_error_location *eloc) {
|
|
inter_tree_node *P = Inode::new_with_0_data_fields(IBM, NOP_IST,
|
|
eloc, level);
|
|
inter_error_message *E = VerifyingInter::instruction(InterBookmark::package(IBM), P);
|
|
if (E) return E;
|
|
NodePlacement::move_to_moving_bookmark(P, IBM);
|
|
return NULL;
|
|
}
|
|
|
|
@h Writing to textual Inter syntax.
|
|
The |nop| construct is not expressible in textual Inter, but can be printed out
|
|
all the same, purely so that a stack backtrace will show it.
|
|
|
|
=
|
|
void NopInstruction::write(inter_construct *IC, OUTPUT_STREAM, inter_tree_node *P) {
|
|
WRITE("nop");
|
|
}
|