Up: Notes

Reference

Scanless DSL as of 2017-02-23

Found Marpa.R2.DSL.Structure. TODO: Check against my tables below.

Comparison charts

Adverb/User Comparison Chart

Notes and questions

1. A close reading of DSL.pod is necessary to find that empty rules are considered to be a special case of an rhs alternative. See Scanless DSL: empty rule

IMHO this part needs an emphasis of some kind, as it makes reading the remainder of the document easier, whenever it talks about RHS alternatives.

The role of quantified rules should be clarified too I believe. In some places I believe that an adverb applies to quantified rules as well, with this not explicitly stated (See "name", "action", "bless").

1. It should be noted that while some of the descriptions of adverbs and context cross-confirm each other, not all them do. I will use the marker XREF whereever I put information into a table which came from the other description and is thus not cross-confirmed.

2. On another note, while the provided meta-grammer using a single set of rules for the adverbs, thus moving validation of their applicability past the parser, I see it as possible to give each context its own variant of <adverb list> which references only the allowed adverbs for that context. That way there is no need to validate past the parser, the grammar ensured it already. And this would be a third cross-check against the human-readable descriptions.

Strongly tempted to make that happen here.

1. "The action adverb is allowed for An RHS alternative, in which the action is for the alternative."

This feels incomplete. Nothing is said about quantified rules. While empty rules are not mentioned either

Note also that it is explicitly specified to not be allowed for L0 rules at all.

1. Technically it seems that rules with precedence are possible for L0. It does not really make sense, as the structure of the matched lexeme will not be affected by this, but still.

So, is the "assoc" adverb allowed in L0 priority rule/alternatives ?

1. Is the "name" adverb allowed for quantified rules ?

2. Nothing is said at all about where the "rank" adverb is allowed, or not.

Adverbs

Adverb	Notes
action	Scanless DSL: action
association	Scanless DSL: assoc
bless	Scanless DSL: bless
event	Scanless DSL: event
latm	Scanless DSL: latm
name	Scanless DSL: name
null-ranking	Scanless DSL: null-ranking
pause	Scanless DSL: pause
priority	Scanless DSL: priority
proper	Scanless DSL: proper
rank	Scanless DSL: rank
separator	Scanless DSL: separator

Adverb contexts

Context	Notes
:default	Scanless DSL: :default
:discard	Scanless DSL: :discard
:lexeme	Scanless DSL: :lexeme
discard default	Scanless DSL: discard default
g1 alternative	Scanless DSL: alternative
g1 empty rule	Scanless DSL: empty rule
g1 quant. rule	Scanless DSL: quantified rule
l0 alternative	Scanless DSL: alternative
l0 empty rule	Scanless DSL: empty rule
l0 quant. rule	Scanless DSL: quantified rule
lexeme default	Scanless DSL: lexeme default

Adverbs versus possible contexts

Note that empty rules are not considered separately here due to them being a special case of an RHS alternative. That makes the table a bit shorter.

Adverb	Context	Notes
action		Scanless DSL: action
	:default	yes (XREF: G1)
	:discard
	:lexeme
	discard default
	g1 alternative	yes - Applies to the alternative
	g1 quant. rule	XREF: yes
	l0 alternative	no
	l0 quant. rule	no
	lexeme default	yes - For all lexemes which do not specifically set their own
association		Scanless DSL: assoc
	:default
	:discard
	:lexeme
	discard default
	g1 alternative	yes
	g1 quant. rule
	l0 alternative
	l0 quant. rule
	lexeme default
bless		Scanless DSL: bless
	:default	XREF: yes, G1
	:discard
	:lexeme
	discard default
	g1 alternative	? XREF: yes
	g1 quant. rule	?
	l0 alternative	?
	l0 quant. rule	?
	lexeme default	XREF: yes
event		Scanless DSL: event
	:default
	:discard	XREF: yes, discard event
	:lexeme	yes - Names the event for 'pause'. Error if 'pause' is missing.
	discard default	XREF: yes
	g1 alternative
	g1 quant. rule
	l0 alternative
	l0 quant. rule
	lexeme default
latm		Scanless DSL: latm
	:default
	:discard
	:lexeme	yes
	discard default
	g1 alternative
	g1 quant. rule
	l0 alternative
	l0 quant. rule
	lexeme default	yes
name		Scanless DSL: name
	:default
	:discard
	:lexeme
	discard default
	g1 alternative	yes
	g1 quant. rule
	l0 alternative	yes
	l0 quant. rule
	lexeme default
null-ranking		Scanless DSL: null-ranking
	:default
	:discard
	:lexeme
	discard default
	g1 alternative
	g1 quant. rule	yes
	l0 alternative	no
	l0 quant. rule	no
	lexeme default
pause		Scanless DSL: pause
	:default
	:discard
	:lexeme	yes - Declares a parse event. (Self: Warn if "event" is missing, unnamed events are strongly discouraged)
	discard default
	g1 alternative
	g1 quant. rule
	l0 alternative
	l0 quant. rule
	lexeme default
priority		Scanless DSL: priority
	:default
	:discard
	:lexeme	yes
	discard default
	g1 alternative
	g1 quant. rule
	l0 alternative
	l0 quant. rule
	lexeme default
proper		Scanless DSL: proper
	:default
	:discard
	:lexeme
	discard default
	g1 alternative
	g1 quant. rule	yes - Ignored if there is no "separator". (Self: Add warning)
	l0 alternative
	l0 quant. rule	yes - Ignored if there is no "separator". (Self: Add warning)
	lexeme default
rank		Scanless DSL: rank
	:default
	:discard
	:lexeme
	discard default
	g1 alternative
	g1 quant. rule
	l0 alternative
	l0 quant. rule
	lexeme default
separator		Scanless DSL: separator
	:default
	:discard
	:lexeme
	discard default
	g1 alternative
	g1 quant. rule	yes
	l0 alternative
	l0 quant. rule	yes
	lexeme default

Possible contexts versus adverbs

Context	Adverb	Notes
:default		Scanless DSL: :default
	action	yes - Affects G1 rules
	association
	bless	yes - Affects G1 rules
	event
	latm
	name
	null-ranking
	pause
	priority
	proper
	rank
	separator
:discard		Scanless DSL: :discard
	action
	association
	bless
	event	yes - L0 - Implies a pause (discard event only)
	latm
	name
	null-ranking
	pause
	priority
	proper
	rank
	separator
:lexeme		Scanless DSL: :lexeme
	action
	association
	bless
	event	yes - L0 - If specified, pause has to be as well. Error if not
	latm	XREF: yes
	name
	null-ranking
	pause	yes - L0 - If specified, event should be as well. Unnamed events are discouraged
	priority	yes
	proper
	rank
	separator
discard default		Scanless DSL: discard default
	action
	association
	bless
	event	yes
	latm
	name
	null-ranking
	pause
	priority
	proper
	rank
	separator
g1 alternative		Scanless DSL: Alternatives
	action	yes
	association	yes
	bless	yes
	event
	latm
	name	XREF: yes
	null-ranking
	pause
	priority
	proper
	rank
	separator
g1 empty rule		Scanless DSL: Empty rules
	action	yes
	association	XREF: yes
	bless	yes
	event
	latm
	name	XREF: yes
	null-ranking
	pause
	priority
	proper
	rank
	separator
g1 quant. rule		Scanless DSL: Quantified
	action	yes
	association
	bless	yes
	event
	latm
	name
	null-ranking
	pause
	priority
	proper	yes
	rank
	separator	yes
l0 alternative		Scanless DSL: Alternatives
	action	XREF: no
	association	yes__?__
	bless
	event
	latm
	name	XREF: yes
	null-ranking
	pause
	priority
	proper
	rank
	separator
l0 empty rule		Scanless DSL: Empty rules
	action	XREF: no
	association	yes__?__
	bless
	event
	latm
	name	XREF: yes
	null-ranking
	pause
	priority
	proper
	rank
	separator
l0 quant. rule		Scanless DSL: Quantified
	action	XREF: no
	association
	bless
	event
	latm
	name
	null-ranking
	pause
	priority
	proper	yes
	rank
	separator	yes
lexeme default		Scanless DSL: lexeme default
	action	yes - L0
	association
	bless	yes - L0
	event
	latm	yes - L0
	name
	null-ranking
	pause
	priority
	proper
	rank
	separator