"whether" on "global"

[sylvainkahane]

Currently, "whether" only concerns a pattern. It is not possible to ask to grew-match whether global { social_context=private }, whether global{ text=re"And.*" } and so on.
It would be particularly interesting to have this to simplify the implementation of Grex, where we often ask a question on metadata as soon we use Grex to induce contrastive grammars.

[bguil]

Since version 1.18 of grewlib, all the "global" contraints can also be expressed in the clauses pattern, with, without and in the whether clustering (see doc).

With the new syntax, the indentifiers global and meta are reserved:
Here are a few equivalence:

Old syntax	New syntax
global { social_context=private }	pattern { meta.social_context=private }
global { text=re"And.*" }	pattern { meta.text=re"And.*" }
global { is_tree }	pattern { global.is_tree }
No syntax for the absence of a meta key	pattern { !meta.speaker }

A few examples with use of global/meta for clustering:

• social_context=private
• text starting with "And"
• 9.13% of non projective structures in SUD_French-GSD