check in interface.jl

Author: shashi

src/interface.jl

@@ -0,0 +1,82 @@
+"""
+  istree(x)
+
+Returns `true` if `x` is a term. If true, `operation`, `arguments`
+must also be defined for `x` appropriately.
+"""
+istree(x) = false
+
+"""
+  symtype(x)
+
+Returns the symbolic type of `x`. By default this is just `typeof(x)`.
+Define this for your symbolic types if you want `SymbolicUtils.simplify` to apply rules
+specific to numbers (such as commutativity of multiplication). Or such
+rules that may be implemented in the future.
+"""
+function symtype(x)
+  typeof(x)
+end
+
+"""
+  issym(x)
+
+Returns `true` if `x` is a symbol. If true, `nameof` must be defined
+on `x` and must return a Symbol.
+"""
+issym(x) = false
+
+"""
+  operation(x)
+
+If `x` is a term as defined by `istree(x)`, `operation(x)` returns the
+head of the term if `x` represents a function call, for example, the head
+is the function being called.
+"""
+function operation end
+
+"""
+  arguments(x)
+
+Get the arguments of `x`, must be defined if `istree(x)` is `true`.
+"""
+function arguments end
+
+"""
+  unsorted_arguments(x::T)
+
+If x is a term satisfying `istree(x)` and your term type `T` orovides
+and optimized implementation for storing the arguments, this function can 
+be used to retrieve the arguments when the order of arguments does not matter 
+but the speed of the operation does.
+"""
+unsorted_arguments(x) = arguments(x)
+arity(x) = length(unsorted_arguments(x))
+
+"""
+  metadata(x)
+
+Return the metadata attached to `x`.
+"""
+metadata(x) = nothing
+
+"""
+  metadata(x, md)
+
+Returns a new term which has the structure of `x` but also has
+the metadata `md` attached to it.
+"""
+function metadata(x, data)
+  error("Setting metadata on $x is not possible")
+end
+
+"""
+  similarterm(x, head, args, symtype=nothing; metadata=nothing, exprhead=:call)
+
+Returns a term that is in the same closure of types as `typeof(x)`,
+with `head` as the head and `args` as the arguments, `type` as the symtype
+and `metadata` as the metadata. By default this will execute `head(args...)`.
+`x` parameter can also be a `Type`. The `exprhead` keyword argument is useful 
+when manipulating `Expr`s.
+"""
+function similarterm end