Define constant kind of symbolic item.

Author: lamorton

src/constants.jl

@@ -0,0 +1,36 @@
+import SymbolicUtils: symtype, term, hasmetadata, issym
+struct MTKConstantCtx end
+
+function isconstant(x)
+    x = unwrap(x)
+    x isa Symbolic &&  getmetadata(x, MTKConstantCtx, false)
+end
+
+"""
+    toconst(s::Sym)
+
+Maps the parameter to a constant. The parameter must have a default.
+"""
+function toconst(s)
+    if s isa Symbolics.Arr
+        Symbolics.wrap(toconst(Symbolics.unwrap(s)))
+    elseif s isa AbstractArray
+        map(toconst, s)
+    else
+        assert(hasmetadata(s,VariableDefaultValue))
+        setmetadata(s, MTKConstCtx, true)
+    end
+end
+toconst(s::Num) = wrap(toconst(value(s)))
+
+"""
+$(SIGNATURES)
+
+Define one or more known variables.
+"""
+macro constants(xs...)
+    Symbolics._parse_vars(:constants,
+                          Real,
+                          xs,
+                          toconst) |> esc
+end