comm rule:

xi =_N xi' =>

R + for(x1 <- y1; ...; xN <- yN)P + S
| y1'!(Q1) | ... | yN'!(QN)

->

P{@Q1/x1, ..., @QN/yN}


Rholang constructions:

Sends:
x!(P, Q)
x!!(P, Q)

x(P, Q)


Recieves:
for( x1 <- y1 ){ P } : One-time for

for( x1 <= y1 ){ P } : Persistant for
contract y1(x1) = { P } : Persistant for

for( x1 <! y1) { P }: recieve then send
desugars to
for( @x1 <- y1) {
  y1!(x1) |
  P
}

for( x1 << y1; x2 << y2)

for( x1 <- y1 if x1 > 0){ P } : Input filtering

select {
  x1 <- y1; x2 <- y2 if x1 > 0 && x2 < 0 => P

  x1 <- y1 if x1 < 0 => Q

  x1 <- y1 => Z

}


Matching:

match z!(q) {
  case x!(y) => Q {z/x, q/y}

  case for(x <- y) => R
  case _ => D
}


P matches Q

if ( B ) X else y

New names:
new x, y, z in P

Ground Types:
Boolean: true, false
int64: 233, 0, -1
String: "Hello World"
Date / Time: DateTime(2018-05-17T23:14:34+00:00)

[P1, P2]: List
(P1, P2): Tuple
Set(P1, P2): Set

[P1, P2].getItem(0)