NewExpander creates an Expander that acts like regexp.Regexp.Expand().

Empty is an empty template.

Expander provides a precompiled and generic alternative to regexp.Regexp.Expand() Expander instances contain no buffer and may be copied or concurrently used.

PartProvider represents a function to provide the value for a given part, from the source of template.

RecordType is the type of records as source of string expansion.

VariableResolverCreator represents a function to create PartProvider from variable name.