[feature request] refactoring (or is the code intentional?)

[guicho271828]

• Implement a wrapper layer that converts the input arrays to the assumed type
• Using typed structure slots to remove some explicit type declarations
  • alternatively, replace the accessor calls to Trivia pattern matcher which always bind variables to slot values with type declarations obtained from MOP
  • Is the current lack of type declarations in the structure definitions intentional? Performance considerations for CCL?
• Some loops can be replaced with map-into, replace etc. SBCL can open-code them into loops (but not in CCL?)