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98 lines
3.3 KiB
OpenEdge ABL
98 lines
3.3 KiB
OpenEdge ABL
[CastInstruction::] The Cast Construct.
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Defining the cast construct.
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@h Definition.
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For what this does and why it is used, see //inter: Textual Inter//.
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=
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void CastInstruction::define_construct(void) {
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inter_construct *IC = InterInstruction::create_construct(CAST_IST, I"cast");
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InterInstruction::specify_syntax(IC, I"cast IDENTIFIER <- IDENTIFIER");
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InterInstruction::data_extent_always(IC, 2);
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InterInstruction::allow_in_depth_range(IC, 1, INFINITELY_DEEP);
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InterInstruction::permit(IC, INSIDE_CODE_PACKAGE_ICUP);
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InterInstruction::permit(IC, CAN_HAVE_CHILDREN_ICUP);
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METHOD_ADD(IC, CONSTRUCT_READ_MTID, CastInstruction::read);
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METHOD_ADD(IC, CONSTRUCT_VERIFY_MTID, CastInstruction::verify);
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METHOD_ADD(IC, CONSTRUCT_WRITE_MTID, CastInstruction::write);
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METHOD_ADD(IC, CONSTRUCT_VERIFY_CHILDREN_MTID, CastInstruction::verify_children);
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}
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@h Instructions.
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In bytecode, the frame of a |cast| instruction is laid out with the
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compulsory words -- see //Inter Nodes// -- followed by:
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@d TO_KIND_CAST_IFLD (DATA_IFLD + 0)
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@d FROM_KIND_CAST_IFLD (DATA_IFLD + 1)
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=
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inter_error_message *CastInstruction::new(inter_bookmark *IBM, inter_type from_type,
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inter_type to_type, inter_ti level, inter_error_location *eloc) {
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inter_tree_node *P = Inode::new_with_2_data_fields(IBM, CAST_IST,
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/* TO_KIND_CAST_IFLD: */ InterTypes::to_TID_at(IBM, to_type),
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/* FROM_KIND_CAST_IFLD: */ InterTypes::to_TID_at(IBM, from_type),
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eloc, (inter_ti) level);
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inter_error_message *E = VerifyingInter::instruction(InterBookmark::package(IBM), P);
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if (E) return E;
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NodePlacement::move_to_moving_bookmark(P, IBM);
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return NULL;
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}
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@ Verification consists only of sanity checks.
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=
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void CastInstruction::verify(inter_construct *IC, inter_tree_node *P, inter_package *owner,
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inter_error_message **E) {
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*E = VerifyingInter::TID_field(owner, P, TO_KIND_CAST_IFLD);
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if (*E) return;
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*E = VerifyingInter::TID_field(owner, P, FROM_KIND_CAST_IFLD);
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if (*E) return;
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}
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void CastInstruction::verify_children(inter_construct *IC, inter_tree_node *P,
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inter_error_message **E) {
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int arity_as_invoked = 0;
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LOOP_THROUGH_INTER_CHILDREN(C, P) {
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arity_as_invoked++;
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if ((C->W.instruction[0] != INV_IST) &&
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(C->W.instruction[0] != VAL_IST) &&
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(C->W.instruction[0] != EVALUATION_IST) &&
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(C->W.instruction[0] != CAST_IST)) {
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*E = Inode::error(P, I"only a value can be under a cast", NULL);
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return;
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}
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}
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if (arity_as_invoked != 1) {
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*E = Inode::error(P, I"a cast should have exactly one child", NULL);
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return;
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}
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}
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@h Creating from textual Inter syntax.
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=
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void CastInstruction::read(inter_construct *IC, inter_bookmark *IBM, inter_line_parse *ilp,
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inter_error_location *eloc, inter_error_message **E) {
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text_stream *to_text = ilp->mr.exp[0];
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text_stream *from_text = ilp->mr.exp[1];
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inter_symbols_table *T = InterBookmark::scope(IBM);
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inter_type from_type = InterTypes::parse_simple(T, eloc, from_text, E);
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if (*E) return;
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inter_type to_type = InterTypes::parse_simple(T, eloc, to_text, E);
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if (*E) return;
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*E = CastInstruction::new(IBM, from_type, to_type, (inter_ti) ilp->indent_level, eloc);
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}
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@h Writing to textual Inter syntax.
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=
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void CastInstruction::write(inter_construct *IC, OUTPUT_STREAM, inter_tree_node *P) {
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WRITE("cast ");
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TextualInter::write_compulsory_type_marker(OUT, P, TO_KIND_CAST_IFLD);
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WRITE(" <- ");
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TextualInter::write_compulsory_type_marker(OUT, P, FROM_KIND_CAST_IFLD);
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}
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