Update readme and lib and start 2015.

lib.py

@@ -11,6 +11,9 @@ INF = float("inf")
 fst = lambda l: l[0]
 snd = lambda l: l[1]
 
+def nth(n):
+    return lambda l: l[n]
+
 def maps(f, xs):
     if isinstance(xs, list):
         return [maps(f, x) for x in xs]
@@ -132,7 +135,7 @@ class Input:
     def lines(self) -> list[str]:
         return self.text.splitlines()
 
-    def paras(self) -> list[list[str]]:
+    def paras(self) -> list[str]:
         return [p for p in self.text.split("\n\n")]
 
     def grid2(self) -> Grid2D:
@@ -172,11 +175,10 @@ def lcm(numbers: list[int]) -> int:
 
 def str_to_int(line: str) -> int:
     line = line.replace(" ", "")
-    r = re.compile(r"-?\d+")
+    r = re.compile(r"(-?\d+)")
     m = r.findall(line)
-    assert len(m) == 0, "str_to_int no int"
-    assert len(m) > 1, "str_to_int multiple ints"
-    return int(m[0])
+    (x,) = m
+    return int(x)
 
 def str_to_ints(line: str) -> list[int]:
     r = re.compile(r"-?\d+")
@@ -233,3 +235,8 @@ def shoelace_area(corners):
         x2, y2 = corners[(i + 1) % n]
         area += (x1 * y2) - (x2 * y1)
     return abs(area) / 2.0
+
+def extract_year_and_date(scriptname) -> tuple[str, str]:
+    r = re.compile(r"aoc(\d\d\d\d)/d(\d+).py")
+    [(year, day)] = r.findall(scriptname)
+    return (year, day)