refact: convert backent into a class

This allows better integration, and to define a
compliance interface via an ABC which, fortunately,
will help others to create other backends.

Author: boriel

src/arch/interface/__init__.py

@@ -0,0 +1,32 @@
+from abc import ABC, abstractmethod
+
+__all__ = ("BackendInterface",)
+
+
+class BackendInterface(ABC):
+    """Generic Backend interface"""
+
+    def __init__(self):
+        self.init()
+
+    @abstractmethod
+    def init(self) -> None:
+        """Initializes this module"""
+
+    @staticmethod
+    @abstractmethod
+    def emit_prologue() -> list[str]:
+        """Emits Program Start routine"""
+
+    @staticmethod
+    @abstractmethod
+    def emit_epilogue() -> list[str]:
+        """Emits Program End routine"""
+
+    @abstractmethod
+    def emit(self, *, optimize: bool = True) -> list[str]:
+        """Begin converting each quad instruction to asm
+        by iterating over the "mem" array, and called its
+        associated function. Each function returns an array of
+        ASM instructions
+        """

src/arch/interface/backend.py

@@ -0,0 +1,35 @@
+from dataclasses import dataclass
+
+from src.symbols.symbol_ import Symbol
+
+__all__ = ("Quad",)
+
+
+@dataclass(init=False, frozen=True)
+class Quad:
+    """Implements a Quad code instruction."""
+
+    instr: str
+    args: tuple[str, ...]
+
+    def __init__(self, instr: str, *args) -> None:
+        """Creates a quad-uple checking it has the current params.
+        Operators should be passed as Quad(ICInstruction, tSymbol, val1, val2)
+        """
+        args = tuple(str(x.t) if isinstance(x, Symbol) else str(x) for x in args)
+        object.__setattr__(self, "instr", instr)
+        object.__setattr__(self, "args", args)
+
+    def __str__(self) -> str:
+        """String representation"""
+        return f"({self.instr} {', '.join(x for x in self.args)})"
+
+    def __len__(self) -> int:
+        """Returns the number of arguments + 1 (the instruction)"""
+        return len(self.args) + 1
+
+    def __iter__(self):
+        return iter((self.instr, *self.args))
+
+    def __getitem__(self, item):
+        return (self.instr, *self.args)[item]