Parser Impl
# The following YAML grammar is LL(1) and is parsed by a recursive descent parser.
stream ::= STREAM-START implicit_document? explicit_document* STREAM-END
implicit_document ::= block_node DOCUMENT-END*
explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
block_node_or_indentless_sequence ::=
ALIAS
| properties (block_content | indentless_block_sequence)?
| block_content
| indentless_block_sequence
block_node ::= ALIAS
| properties block_content?
| block_content
flow_node ::= ALIAS
| properties flow_content?
| flow_content
properties ::= TAG ANCHOR? | ANCHOR TAG?
block_content ::= block_collection | flow_collection | SCALAR
flow_content ::= flow_collection | SCALAR
block_collection ::= block_sequence | block_mapping
flow_collection ::= flow_sequence | flow_mapping
block_sequence ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
indentless_sequence ::= (BLOCK-ENTRY block_node?)+
block_mapping ::= BLOCK-MAPPING_START
((KEY block_node_or_indentless_sequence?)?
(VALUE block_node_or_indentless_sequence?)?)*
BLOCK-END
flow_sequence ::= FLOW-SEQUENCE-START
(flow_sequence_entry FLOW-ENTRY)*
flow_sequence_entry?
FLOW-SEQUENCE-END
flow_sequence_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
flow_mapping ::= FLOW-MAPPING-START
(flow_mapping_entry FLOW-ENTRY)*
flow_mapping_entry?
FLOW-MAPPING-END
flow_mapping_entry ::= flow_node | KEY flow_node? (VALUE flow_node?)?
#
FIRST sets:
#
stream: { STREAM-START }
explicit_document: { DIRECTIVE DOCUMENT-START }
implicit_document: FIRST(block_node)
block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START }
flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START }
block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START }
flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
block_sequence: { BLOCK-SEQUENCE-START }
block_mapping: { BLOCK-MAPPING-START }
block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY }
indentless_sequence: { ENTRY }
flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
flow_sequence: { FLOW-SEQUENCE-START }
flow_mapping: { FLOW-MAPPING-START }
flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
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Since writing a recursive-descendant parser is a straightforward task, we do not give many comments here.
Parameters
settings
tokenizer