improve compatibility with older python 3 versions

ast.py

@@ -1,6 +1,6 @@
 # fx-92 Scientifique Collège+ language interpreter: AST definition
 
-import enum
+import aenum as enum
 
 #---
 # Internal AST node representation
@@ -58,9 +58,9 @@ class Node:
             return str(self.value)
         try:
             name = N(self.type).name
-            return f"<Node:{name}>"
+            return "<Node:{}>".format(name)
         except ValueError:
-            return f"<Node:{hex(self.type)}>"
+            return "<Node:{}>".format(hex(self.type))
 
     @property
     def value(self):

fx92.py

@@ -13,8 +13,8 @@ from interpreter import Context
 # Main program
 #---
 
-usage_string = f"""
-usage: {sys.argv[0]} [-s|-u] <file> [options...]
+usage_string = """
+usage: {} [-s|-u] <file> [options...]
 
 If "-" is specified as input, stdin is read.
 
@@ -26,7 +26,7 @@ Output options:
   --quiet        Do not show the SDL window
   --save=<file>  Save a copy of the screen output in a bitmap file
   --scale=<n>    Window scale up (default 4, max 16)
-""".strip()
+""".format(sys.argv[0]).strip()
 
 def usage(exitcode=None):
     print(usage_string, file=sys.stderr)
@@ -55,7 +55,7 @@ def main():
 
     except getopt.GetoptError as e:
         print("error:", e, file=sys.stderr)
-        print(f"Try '{sys.argv[0]} --help' for details.", file=sys.stderr)
+        print("Try '{} --help' for details.".format(sys.argv[0]), file=sys.stderr)
         sys.exit(1)
 
     # Other parameters

interpreter.py

@@ -212,7 +212,7 @@ class Context:
             }[n.args[0]]
 
             if f is None:
-                raise Exception(f"Function {n.args[0]} not there yet x_x")
+                raise Exception("Function {} not there yet x_x".format(n.args[0]))
             return f(arg)
 
         elif n.type == N.REL:
@@ -230,7 +230,7 @@ class Context:
 
         else:
             t = N(n.type).name
-            raise Exception(f"Unhandled node of type {t}")
+            raise Exception("Unhandled node of type {}".format(t))
 
     def runs(self, n):
         """Evaluate all the arguments of a node."""

lexer.py

@@ -81,7 +81,7 @@ class Token:
         try:
             base = T(self.type).name
         except ValueError:
-            base = f"<Token:{hex(self.type)}>"
+            base = "<Token:{}>".format(hex(self.type))
 
         if self.args:
             args = "(" + ",".join(repr(arg) for arg in self.args) + ")"
@@ -140,7 +140,7 @@ class BitcodeLexer(LexerBase):
         if h[p] in [0xF9, 0xFB]:
             # Stop if there is no trailing byte
             if p >= len(h) - 1:
-                print(f"[lexer] Invalid trailing byte {hex(h[p])}")
+                print("[lexer] Invalid trailing byte {}".format(hex(h[p])))
                 p = len(h)
                 return Token(T.END)
 
@@ -158,7 +158,7 @@ class BitcodeLexer(LexerBase):
             if h[p] == 0xFB and h[p+1] in rels:
                 return Token(T.REL, rels[h[p+1]])
 
-            print(f"[lexer] Unknown opcode {hex(code)}")
+            print("[lexer] Unknown opcode {}".format(hex(code)))
             self.errors += 1
 
             # Try to read another token
@@ -190,11 +190,11 @@ class BitcodeLexer(LexerBase):
             match = re.match(re_const, h[p:])
 
             if match is not None:
-                text = match[1].replace(b'\x2E', b'.').replace(b'\x2D', b'e')
+                text = match.group(1).replace(b'\x2E', b'.').replace(b'\x2D', b'e')
                 self.pos += len(text) - 1
 
                 f = float(text.decode('utf-8'))
-                if match[2] == "%":
+                if match.group(2) == "%":
                     f /= 100
                 return Token(T.CONST, f)
 
@@ -241,7 +241,7 @@ class BitcodeLexer(LexerBase):
         if code in fun:
             return Token(T.FUN, fun[code])
 
-        print(f"[lexer] Unknown opcode {hex(code)}")
+        print("[lexer] Unknown opcode {}".format(hex(code)))
         self.errors += 1
 
         # Try to read another token after skipping one byte
@@ -283,7 +283,6 @@ class UrlLexer(BitcodeLexer):
 
         if not re.fullmatch(r'(?:[0-9a-fA-F]{2})+', url):
             print("[urlparser] URL is not strict hexa, noise will be skipped")
-
         super().__init__(bytes.fromhex(url))
 
 #---
@@ -397,7 +396,7 @@ class TextLexer(LexerBase):
         err = s[0]
         self.code = s[1] if len(s) > 1 else ""
 
-        raise Exception(f"Lexical error near '{err}'")
+        raise Exception("Lexical error near '{}'".format(err))
 
     def at_end(self):
         """Check whether the whole input has been read."""

parser.py

@@ -74,7 +74,7 @@ class Parser:
         expected = [T(t).name for t in types]
         got = T(self.la.type).name
         pos = self.lexer.position
-        err = f"Expected one of {expected}, got {got} (at token {pos})"
+        err = "Expected one of {}, got {} (at token {})".format(expected, got, pos)
         print("[urlparser] " + err)
         raise Exception("Syntax error: " + err)
 

printer.py

@@ -42,7 +42,7 @@ def print_ast(n, lang="en", indent=0):
     print(" " * indent, end="")
 
     if not isinstance(n, Node):
-        print(f"{type(n)}({n})")
+        print("{}({})".format(type(n), n))
         return
 
     if n.type in [N.CONST, N.VAR, N.REL]:
@@ -54,7 +54,7 @@ def print_ast(n, lang="en", indent=0):
     if hasattr(lang, id):
         print(getattr(lang, id).format(*n.args))
     else:
-        print(f"{n.type.name}")
+        print("{}".format(n.type.name))
 
     if n.type in [N.FORWARD, N.ROTATE, N.ORIENT, N.GOTO] and \
         n.constchildren():
@@ -63,7 +63,7 @@ def print_ast(n, lang="en", indent=0):
     if n.type == N.ASSIGN:
         print_ast(n.args[0], lang=lang, indent=indent+2)
         print(" " * (indent+2), end="")
-        print(f"->{n.args[1]}")
+        print("->{}".format(n.args[1]))
         return
 
     for arg in n.args: