TODO

=> Meshing roadmap
* the road to 3MF slice export
  * add SVG export

Bug: REPL aborts if viewer cannot be opened.

=> Pairs
=> Collections (requires Pairs)

Document `var!newval`.

Document 'parametric' better, as a general way to specify parameters of
a shape. Add `-Pid=value` to override shape parameters on command line.

Document 'term' phrases. Tight and loose formatting style.
In Records doc, call out 'R.a' vs 'R .a' style of field selection.

Clean up documentation
* remove or fix anything from docs directory that is old or out of date.
* make sure everything in the version 0.5 release notes is documented.

make_shape documentation:
* the fields of a shape value
* The t in [x,y,z,t] means the time in seconds since the beginning of the animation. This lets you create animated shapes.
* Distance functions are written in a staticallly typed, restricted subset of Curv which is called "SubCurv". Unfortunately, curried functions like quadratic p0 p1 p2 w0 w1 w2 t are not yet supported in SubCurv. You must instead use quadratic [p0, p1, p2, w0, w1, w2, t]: use a single argument that is a list.

Tutorials:
* translating GLSL into Curv
* fillets and rounds
* blob & skeleton based modelling
* strokes & sweeps

transliterating GLSL into Curv -- docs/language/GLSL_to_Curv.rst
   float x = 1.0;   =>    local x = 1;
   x = x + 1;       =>    x := x + 1;
   v.x  =>   v.[X]
   v.xy =>  v.[[X,Y]]
   dot(v1,v2)  =>  dot[v1,v2]
   vec(x,y)  =>  [x,y]

---------
* auto detection of c++ compiler for '-O jit' default value

Finish imperative:
* document local
* unit tests
* Imperative.rst

Finish boolean arrays:
* SubCurv: unit tests for 3 cases of and/or
* general arrays of bool and bool32
* fix TODOs in array_op.h
* binary boolean op: mixed bool/bool32 operations

Primitives API:
* The Context describes the call syntax: 'f x', '-x', 'x `f` y', 'x + y'.
  A more specific argument Location is extracted from the syntax when throwing
  an exception concerning a bad argument.
* Can builtins be implemented in Curv?
* Will a macro simplify the definition of And_Prim?
* define Operation classes using Prim?

Bool_Array : vectorized boolean operators
* <, <=, >, >= work elementwise on arrays.
* `are_equal(a,b)`: elementwise variant of a==b
* `are_unequal(a,b)`: elementwise variant of a!=b.
  Elements are scalars (non-list values).
  Equivalent to xor(a,b) when applied to boolean arrays.
* `select`: vectorized version of `if`
* Maybe define `bit b = select(b, 1, 0)`.
* SubCurv supports bool[2-4] and vectorized boolean ops
* unit tests for operations on reactive values
  * Right now, reactive values are only generated when compiling a parametric
    shape to GLSL. I could create a builtin implementing the same logic.
    * Take a parametric record as argument, compile the parameters to reactive
      values, then call the record's main() function.
    * A builtin that compiles a Curv value into machine code via C++.
      Special handling for parametric records which tests reactive values.