refactor: mark variable default manipulation functions as public

Author: AayushSabharwal

docs/src/API/variables.md

@@ -18,6 +18,17 @@ Symbolic variables can have metadata attached to them. The defaults and guesses
 at variable construction time are examples of this metadata. ModelingToolkit also defines
 additional types of metadata.
 
+## Variable defaults
+
+Variables can be assigned default values to avoid having to specify defaults to the
+[`System`](@ref) constructor.
+
+```@docs
+ModelingToolkit.hasdefault
+ModelingToolkit.getdefault
+ModelingToolkit.setdefault
+```
+
 ## Variable descriptions
 
 Descriptive strings can be attached to variables using the `[description = "descriptive string"]` syntax:

src/ModelingToolkit.jl

@@ -342,7 +342,8 @@ export DynamicOptSolution
 @public VariableType, MTKVariableTypeCtx, VariableBounds, VariableConnectType
 @public VariableDescription, VariableInput, VariableIrreducible, VariableMisc
 @public VariableOutput, VariableStatePriority, VariableUnit, collect_scoped_vars!
-@public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars
+@public collect_var_to_name!, collect_vars!, eqtype_supports_collect_vars, hasdefault
+@public getdefault, setdefault
 
 for prop in [SYS_PROPS; [:continuous_events, :discrete_events]]
     getter = Symbol(:get_, prop)

src/utils.jl

@@ -250,8 +250,23 @@ function iv_from_nested_derivative(x, op = Differential)
     end
 end
 
+"""
+    $(TYPEDSIGNATURES)
+
+Check if the symbolic variable `v` has a default value.
+"""
 hasdefault(v) = hasmetadata(v, Symbolics.VariableDefaultValue)
+"""
+    $(TYPEDSIGNATURES)
+
+Return the default value of symbolic variable `v`.
+"""
 getdefault(v) = value(Symbolics.getdefaultval(v))
+"""
+    $(TYPEDSIGNATURES)
+
+Set the default value of symbolic variable `v` to `val`.
+"""
 function setdefault(v, val)
     val === nothing ? v : wrap(setdefaultval(unwrap(v), value(val)))
 end