From 8fce9ca1e10b89d9cdd16c8ea16c1f74b2829936 Mon Sep 17 00:00:00 2001
From: Chris Rackauckas <accounts@chrisrackauckas.com>
Date: Sat, 27 Jul 2019 10:08:04 -0400
Subject: [PATCH] move indices to subscripts

---
 README.md        | 19 +++++++++----------
 src/utils.jl     |  4 +++-
 src/variables.jl | 17 ++++++++++++++---
 3 files changed, 26 insertions(+), 14 deletions(-)

diff --git a/README.md b/README.md
index 845bae279a..d3f1264441 100644
--- a/README.md
+++ b/README.md
@@ -118,25 +118,24 @@ The `@variables` and `@parameters` macros support this with the following syntax
 julia> @variables x[1:3];
 julia> x
 3-element Array{Operation,1}:
- x[1]()
- x[2]()
- x[3]()
+ x₁()
+ x₂()
+ x₃()
 
 # support for arbitrary ranges and tensors
 julia> @variables y[2:3,1:5:6];
 julia> y
 2×2 Array{Operation,2}:
- y[2,1]()  y[2,6]()
- y[3,1]()  y[3,6]()
-
+    y₂̒₁() y₂̒₆()
+    y₃̒₁() y₃̒₆()
 
 # also works for dependent variables
 julia> @parameters t; @variables z[1:3](t);
 julia> z
 3-element Array{Operation,1}:
- z[1](t())
- z[2](t())
- z[3](t())
+ z₁(t())
+ z₂(t())
+ z₃(t())
  ```
 
 ## Core Principles
@@ -201,7 +200,7 @@ aliased to the given call, allowing implicit use of dependents for convenience.
 @parameters t α σ(..) β[1:2]
 @variables w(..) x(t) y() z(t, α, x)
 
-expr = β[1] * x + y^α + σ(3) * (z - t) - β[2] * w(t - 1)
+expr = β₁* x + y^α + σ(3) * (z - t) - β₂ * w(t - 1)
 ```
 
 Note that `@parameters` and `@variables` implicitly add `()` to values that
diff --git a/src/utils.jl b/src/utils.jl
index 55036a8e0d..ea95696c9c 100644
--- a/src/utils.jl
+++ b/src/utils.jl
@@ -97,7 +97,9 @@ $(SIGNATURES)
 Generate `ODESystem`, dependent variables, and parameters from an `ODEProblem`.
 """
 function modelingtoolkitize(prob::DiffEqBase.ODEProblem)
-    t, = @parameters t; vars = [Variable(Symbol(:x, i))(t) for i in eachindex(prob.u0)]; params = [Variable(Symbol(:α, i); known = true)() for i in eachindex(prob.p)];
+    t, = @parameters t;
+    vars = [Variable(:x, i)(t) for i in eachindex(prob.u0)]
+    params = [Variable(:α,i; known = true)() for i in eachindex(prob.p)]
     D, = @derivatives D'~t
 
     rhs = [D(var) for var in vars]
diff --git a/src/variables.jl b/src/variables.jl
index 8d88d8d660..d3de5e68dd 100644
--- a/src/variables.jl
+++ b/src/variables.jl
@@ -1,5 +1,16 @@
 export Variable, @variables, @parameters
 
+const IndexMap = Dict{Int,Char}(
+            0 => '₀',
+            1 => '₁',
+            2 => '₂',
+            3 => '₃',
+            4 => '₄',
+            5 => '₅',
+            6 => '₆',
+            7 => '₇',
+            8 => '₈',
+            9 => '₉')
 
 """
 $(TYPEDEF)
@@ -20,7 +31,7 @@ struct Variable <: Function
     Variable(name; known = false) = new(name, known)
 end
 function Variable(name, indices...; known = false)
-    var_name = Symbol("$name[$(join(indices, ","))]")
+    var_name = Symbol("$(name)$(join(getindex.((IndexMap,),indices), "̒"))")
     Variable(var_name; known=known)
 end
 
@@ -113,7 +124,7 @@ end
 function _construct_var(var_name, known, call_args)
     if call_args === nothing
         :(Variable($(Meta.quot(var_name)); known = $known)())
-    elseif call_args[end] == :..
+    elseif !isempty(call_args) && call_args[end] == :..
         :(Variable($(Meta.quot(var_name)); known = $known))
     else
         :(Variable($(Meta.quot(var_name)); known = $known)($(call_args...)))
@@ -123,7 +134,7 @@ end
 function _construct_var(var_name, known, call_args, ind)
     if call_args === nothing
         :(Variable($(Meta.quot(var_name)), $ind...; known = $known)())
-    elseif call_args[end] == :..
+    elseif !isempty(call_args) && call_args[end] == :..
         :(Variable($(Meta.quot(var_name)), $ind...; known = $known))
     else
         :(Variable($(Meta.quot(var_name)), $ind...; known = $known)($(call_args...)))