Grammar conditional output

[eamag]

I think it would be cool to have a condition-based grammar. Example: if class=mage weapon=[one of "staff", "ice"], if class=warrior weapon=[one of "sword", "shield"]. I think I have an idea on how to do it in code (similar to guidance or lmql) but is it already possible with current grammar version? I couldn't figure out how...
@ejones @drbh any ideas on this? Thanks!

[ejones]

You can encode conditionals within alternates (|). By placing the dependent parts (the weapon choice in your example) within each alternate, they are conditioned on the start of the alternate (the selected class):

% ./main -m $L13B -p $'Mages and warriors; weapons staff ice sword shield:\n' \
--grammar '
  root ::= character+
  character ::= "class: " (
    "mage weapon: " ("staff" | "ice") |
    "warrior weapon: " ("sword" | "shield")
  ) "\n"
'

main: grammar:
root ::= root_2 
character ::= [c] [l] [a] [s] [s] [:] [ ] character_3 [<U+000A>] 
root_2 ::= character root_2 | character 
character_3 ::= [m] [a] [g] [e] [ ] [w] [e] [a] [p] [o] [n] [:] [ ] character_4 | [w] [a] [r] [r] [i] [o] [r] [ ] [w] [e] [a] [p] [o] [n] [:] [ ] character_5 
character_4 ::= [s] [t] [a] [f] [f] | [i] [c] [e] 
character_5 ::= [s] [w] [o] [r] [d] | [s] [h] [i] [e] [l] [d] 

 Mages and warriors; weapons staff ice sword shield:
class: warrior weapon: shield
class: mage weapon: staff
class: mage weapon: ice
class: mage weapon: ice
class: mage weapon: ice
class: mage weapon: ice
class: mage weapon: ice
class: mage weapon: ice
class: warrior weapon: shield
class: mage weapon: staff