Import/export DSL CFG
Goal symbol is `cfg`, insignificant whitespace is `whitespace`:

cfg:
  statements
statements:
  statement [statements]
statement:
  newline
  comment
  atrule newline
  varstmt newline
  constraint newline
whitespace:
  ` `
  `\t`
newline:
  `\r`
  `\n`
comment:
  /#.*$/m
anywhitespace:
  whitespace
  newline
ident:
  quoted-ident
  unquoted-ident
quoted-ident:
  /'[^']+'/
  can contain anything except single quotes
  must be quoted throughout the input problem
  solver will use name as if without quotes (relevant when reading results or debugging)
unquoted-ident:
  /[^0-9()\[\] \t\n\r,'=][^()\[\'] \t\n\r,=]*/
  cannot result in a literal of this CFG
  cannot result in a keyword part of a literal of this CFG (matrix, distinct, etc)
  cannot start with a digit
idents:
  ident [`,` idents]
number:
  /\d+/
atrule:
  `@custom` ident [`=`] *
  `@custom targets [`=`] all`
  `@custom targets(` idents `)`
  `@mode` mode
*:
  i'm just being lazy. parse through to eol. hand of to special handler for this @rule. todo
mode:
  `constraints`
  `propagators`
varstmt:
  `:` ident [`=`] domain [aliases] mods
aliases:
  alias [aliases]
alias:
  `alias(` ident `)`
domain:
  pair
  `[` `]`
  `[` lohis `]`
  `[` pairs `]`
  `*`
  number
lohis =
  lohi [lohi]
lohi =
  number [`,`] number [`,`]
pair:
  `[` lohi `]`
pairs:
  pair [`,`] [pairs]
mods:
  mod [mods]
mod:
  `@markov` markov
  `@list` prio
  `@max`
  `@mid`
  `@min`
  `@minMaxCycle`
  `@naive`
  `@splitMax`
  `@splitMin`
prio:
  `prio(` expressions `)`
markov:
  marko [markov]
marko:
  matrix
  legend
  expand
matrix:
  `matrix(` "literal" `)`
  the literal is a matrix object that can be evalled like [{vector:[1,0],_boolVarIndex:2},{vector:[0,1]}]
legend:
  `legend(` expressions `)`
expand:
  `expand(` number `)`
constraint:
  expr [cop expr]
  nulcall
expr: // does not return a value (expression statement)
  vexpr [rop vexpr]
vexpr: // value returning expression (var or constant value)
  valcall
  ident
  number
  grouping
expressions:
  expr [[`,`] expressions]
nulcall:
  `distinct(` expressions `)`
  `nall(` expressions `)`
valcall:
  `sum(` expressions `)`
  `product(` expressions `)`
  `all?(` expressions `)`
  `nall?(` expressions `)`
  `none?(` expressions `)`
rop: // reflecting op (not a constraint on its own, but enforces result var state)
  `==?`
  `!=?`
  `<?`
  `<=?`
  `>?`
  `>=?`
  `+`
  `-`
  `*`
  `/`
cop: // constraining op, has no result
  `==`
  `!=`
  `<`
  `<=`
  `>`
  `>=`
  `&`
grouping:
  `(` vexpr `)`
  `(` grouping `)`


There's currently only one semantic rule that we can't codify in the CFG:

- Vars must either be explicitly (through the colon) or implicitly (by being a result var) declared before being used as a value. You cannot implicitly declare and use a constraint in the same statement. It's considered a parse error if a var is used prematurely.


Examples:

## constraint problem export

@custom var-strat = {"_class":"$var_strat_config","type":"naive","inverted":false}

@custom val-strat = min

: v0 = [0 10000] alias(#box1[x])
: v1 = [100 100] alias(#box1[width])
: v2 = [0 10000] alias(#box1[y])
: v3 = [100 100] alias(#box1[height])
: v4 = [610 610] alias(#box2[x])
: v5 = [100 100] alias(#box2[width])
: v6 = [0 10000] alias(#box2[y])
: v7 = [100 100] alias(#box2[height])
: v8 = [100 100]
: v9 = [1 100000000]
: v10 = [1200 1200]
: v11 = [1 100000000]
: v12 = [800 800]
: v13 = [1 100000000]
: v14 = [1 100000000]
: v15 = [590 590]
: v16 = [590 590]
: v17 = [610 610]
: v18 = [0 100000000]
: v19 = [2 2]
: v20 = [400 400]
: v21 = [0 100000000]

v9 = v10 - v1                  # initial: [1 100000000] = [1200 1200] - [100 100]
v0 < v9                        # initial: [0 10000] < [1 100000000]
v11 = v12 - v3                 # initial: [1 100000000] = [800 800] - [100 100]
v2 < v11                       # initial: [0 10000] < [1 100000000]
v13 = v10 - v5                 # initial: [1 100000000] = [1200 1200] - [100 100]
v4 < v13                       # initial: [610 610] < [1 100000000]
v14 = v12 - v7                 # initial: [1 100000000] = [800 800] - [100 100]
v6 < v14                       # initial: [0 10000] < [1 100000000]
v15 = v0 + v1                  # initial: [100 100]5 = [0 10000] + v1
v18 = v3 / v19                 # initial: [0 100000000] = [100 100] / [2 2]
v2 = v20 - v18                 # initial: [0 10000] = [400 400] - [0 100000000]
v21 = v7 / v19                 # initial: [0 100000000] = [100 100] / [2 2]
v6 = v20 - v21                 # initial: [0 10000] = [400 400] - [0 100000000]

@custom targets = all

## end of export



## constraint problem export

@custom var-strat = {"_class":"$var_strat_config","type":"naive","inverted":false}

@custom val-strat = min

: v0 = [5 5] alias(STATE)
: v1 = [0 100] alias(V1) @markov legend(10,100) matrix([{vector:[1,0],_boolVarIndex:2},{vector:[0,1]}])
: v2 = [0 1]
: v3 = [5 5]
: v4 = [0 100] alias(V2) @markov legend(10,100) matrix([{vector:[1,0],_boolVarIndex:5},{vector:[0,1]}])
: v5 = [0 1]
: v6 = [100 100]

v2 = v0 ==? v3                 # initial: [0 1] = [5 5] ==? [5 5]
markov(v1)                     # initial: markov([0 100])
v5 = v0 ==? v6                 # initial: [0 1] = [5 5] ==? [100 100]
markov(v4)                     # initial: markov([0 100])

@custom targets = all

## end of export




## constraint problem export

@custom var-strat = {"_class":"$var_strat_config","type":"naive","inverted":false}

@custom val-strat = min

: v0 = [1 4] alias(V1) @list prio(2 4 3 1)
: v1 = [1 4] alias(V2) @list prio(3 1 4 2)
: v2 = [0 0]

v0 < v1

@custom targets = all

## end of export