use 2-tuple in docs instead of Interval

Author: valentinsulzer

docs/src/systems/PDESystem.md

@@ -39,17 +39,19 @@ PDESystem
 
 Domains are specifying by saying `indepvar in domain`, where `indepvar` is a
 single or a collection of independent variables, and `domain` is the chosen
-domain type. Thus forms for the `indepvar` can be like:
+domain type. A 2-tuple can be used to indicate an `Interval`. 
+Thus forms for the `indepvar` can be like:
 
 ```julia
-t ∈ Interval(0.0,1.0)
+t ∈ (0.0,1.0)
 (t,x) ∈ UnitDisk()
 [v,w,x,y,z] ∈ VectorUnitBall(5)
 ```
 
 #### Domain Types (WIP)
 
-- `Interval(a,b)`: Defines the domain of an interval from `a` to `b`
+- `Interval(a,b)`: Defines the domain of an interval from `a` to `b` (requires explicit
+import from `DomainSets.jl`, but a 2-tuple can be used instead)
 
 ## `discretize` and `symbolic_discretize`
 

src/systems/pde/pdesystem.jl

@@ -28,8 +28,8 @@ bcs = [u(t,0) ~ 0.,# for all t > 0
        Dt(u(0,x)) ~ 0. ] #for all  0 < x < 1]
 
 # Space and time domains
-domains = [t ∈ Interval(0.0,1.0),
-           x ∈ Interval(0.0,1.0)]
+domains = [t ∈ (0.0,1.0),
+           x ∈ (0.0,1.0)]
 
 pde_system = PDESystem(eq,bcs,domains,[t,x],[u])
 ```

test/pde.jl

@@ -9,7 +9,7 @@ eq  = Dt(u(t,x)) ~ Dxx(u(t,x))
 bcs = [u(0,x) ~ - x * (x-1) * sin(x),
            u(t,0) ~ 0, u(t,1) ~ 0]
 
-domains = [t ∈ Interval(0.0,1.0),
-           x ∈ Interval(0.0,1.0)]
+domains = [t ∈ (0.0,1.0),
+           x ∈ (0.0,1.0)]
 
 pdesys = PDESystem(eq,bcs,domains,[t,x],[u])