refact: move code from backend.__init__.py to files

Also convert OP CODES from the peephole evaluator to
enums.

Author: boriel

src/api/global_.py

@@ -8,12 +8,11 @@
 # This program is Free Software and is released under the terms of
 #                    the GNU General License
 # ----------------------------------------------------------------------
-from typing import Dict, List, NamedTuple, Optional, Set, Final
+from typing import Dict, Final, List, NamedTuple, Optional, Set
 
 from src.api.constants import TYPE, LoopType
 from src.api.opcodestemps import OpcodesTemps
 
-
 # ----------------------------------------------------------------------
 # Simple global container for internal constants.
 # Internal constants might be architecture dependant. They're set
@@ -116,9 +115,9 @@ class LoopInfo(NamedTuple):
 BOUND_TYPE = None  # Set to None, so if not set will raise error
 
 # ----------------------------------------------------------------------
-# Data type used for elements size. Must be an integral
+# Data type used for elements size. Must be an integral type
 # ----------------------------------------------------------------------
-SIZE_TYPE: Final[TYPE] = TYPE.ubyte
+SIZE_TYPE: TYPE = TYPE.ubyte
 
 # ----------------------------------------------------------------------
 # CORE namespace (for core runtime library, like FP Calc)
@@ -145,7 +144,7 @@ class LoopInfo(NamedTuple):
 # ----------------------------------------------------------------------
 # Data Type used for string chars index. Must be an integral
 # ----------------------------------------------------------------------
-STR_INDEX_TYPE: Final[TYPE] = TYPE.uinteger
+STR_INDEX_TYPE: TYPE = TYPE.uinteger
 
 # ----------------------------------------------------------------------
 # MIN and MAX str slice index

src/api/utils.py

@@ -34,6 +34,11 @@ def first(iter_: Iterable[T], default: T | None = None) -> T | None:
     return next(iter(iter_), default)
 
 
+def sfirst(iter_: Iterable[T]) -> T:
+    """Return the first element of an Iterable, or fails if it's empty"""
+    return next(iter(iter_))
+
+
 def read_txt_file(fname: str) -> str:
     """Reads a txt file, regardless of its encoding"""
     encodings = ["utf-8-sig", "cp1252"]

src/arch/__init__.py

@@ -4,10 +4,10 @@
 
 import importlib
 
-__all__ = [
+__all__ = (
     "zx48k",
     "zxnext",
-]
+)
 
 AVAILABLE_ARCHITECTURES = __all__
 target = None