diff --git a/lukkari/__init__.py b/lukkari/__init__.py
index 87d5e51..e2f8da1 100644
--- a/lukkari/__init__.py
+++ b/lukkari/__init__.py
@@ -1,7 +1,7 @@
 import datetime
 import sys
 import os.path
-from . import check_date
+from . import dsl
 from . import daterange
 from . import generate_timetable
 from . import parse_coursefile
@@ -37,7 +37,7 @@ def main():
 
 	courses = []
 	for name, info, parsed_filter in courses_parsed:
-		date_filter = check_date.compile(parsed_filter)
+		date_filter = dsl.compile(parsed_filter)
 		courses.append((name, info, date_filter))
 	
 	timetable = generate_timetable.generate_timetable(dates, courses)
diff --git a/lukkari/check_date.py b/lukkari/dsl.py
similarity index 56%
rename from lukkari/check_date.py
rename to lukkari/dsl.py
index 3a60135..7bee5fb 100644
--- a/lukkari/check_date.py
+++ b/lukkari/dsl.py
@@ -7,7 +7,7 @@ class Filters(enum.Enum):
 class Conjunctions(enum.Enum):
 	all, any, none, implies = range(4)
 
-def compile(parsed):
+def to_ir(parsed):
 	assert(len(parsed) >= 1)
 	function, *parameters = parsed
 
@@ -26,7 +26,7 @@ def compile(parsed):
 
 	elif function == 'week':
 		if len(parameters) > 1:
-			return (Conjunctions.any,) + tuple([compile(('week', week)) for week in parameters])
+			return (Conjunctions.any,) + tuple([to_ir(('week', week)) for week in parameters])
 		else:
 			assert(len(parameters) == 1)
 			week_data, = parameters
@@ -37,7 +37,7 @@ def compile(parsed):
 
 	elif function == 'weekday':
 		if len(parameters) > 1:
-			return (Conjunctions.any,) + tuple([compile(('weekday', weekday)) for weekday in parameters])
+			return (Conjunctions.any,) + tuple([to_ir(('weekday', weekday)) for weekday in parameters])
 		else:
 			assert(len(parameters) == 1)
 			weekday, = parameters
@@ -45,50 +45,51 @@ def compile(parsed):
 		return (Filters.is_weekday, weekday)
 
 	elif function == 'and':
-		return (Conjunctions.all,) + tuple([compile(parameter) for parameter in parameters])
+		return (Conjunctions.all,) + tuple([to_ir(parameter) for parameter in parameters])
 
 	elif function == 'or':
-		return (Conjunctions.any,) + tuple([compile(parameter) for parameter in parameters])
+		return (Conjunctions.any,) + tuple([to_ir(parameter) for parameter in parameters])
 
 	elif function == 'not':
-		return (Conjunctions.none,) + tuple([compile(parameter) for parameter in parameters])
+		return (Conjunctions.none,) + tuple([to_ir(parameter) for parameter in parameters])
 
 	elif function == 'if':
 		assert(len(parameters) == 2)
 		condition, then = parameters
-		return (Conjunctions.implies, compile(condition), compile(then))
+		return (Conjunctions.implies, to_ir(condition), to_ir(then))
 
-def check_day_match(day, date_filter):
+def to_lambda(date_filter):
 	assert(len(date_filter) >= 1)
 	function, *parameters = date_filter
-
 	assert(function in Filters or function in Conjunctions)
-	if function == Conjunctions.implies:
-		assert(len(parameters) == 2)
-	elif function in [Filters.in_date_range, Filters.is_weekday]:
-		assert(len(parameters) == 1)
-	else:
-		assert(function in [Conjunctions.all, Conjunctions.any, Conjunctions.none])
 
 	if function == Conjunctions.all:
-		return all(map(lambda parameter: check_day_match(day, parameter), parameters))
+		compiled = [to_lambda(parameter) for parameter in parameters]
+		return lambda day: all(map(lambda f: f(day), compiled))
 
 	elif function == Conjunctions.any:
-		return any(map(lambda parameter: check_day_match(day, parameter), parameters))
-
+		compiled = [to_lambda(parameter) for parameter in parameters]
+		return lambda day: any(map(lambda f: f(day), compiled))
+	
 	elif function == Conjunctions.implies:
-		left, right = parameters
-		left_truth = check_day_match(day, left)
-		right_truth = check_day_match(day, right)
-		return left_truth and right_truth or not left_truth
-
+		assert(len(parameters) == 2)
+		left, right = to_lambda(parameters[0], parameters[1])
+		return lambda day: right(day) if left(day) else True
+	
 	elif function == Conjunctions.none:
-		return not any(map(lambda parameter: check_day_match(day, parameter), parameters))
-
+		compiled = [to_lambda(parameter) for parameter in parameters]
+		return lambda day: not any(map(lambda f: f(day), compiled))
+	
 	elif function == Filters.in_date_range:
+		assert(len(parameters) == 1)
 		date_range, = parameters
-		return day in date_range
-
+		return lambda day: day in date_range
+	
 	elif function == Filters.is_weekday:
+		assert(len(parameters) == 1)
 		weekday, = parameters
-		return day.isoweekday() == weekday
+		return lambda day: day.isoweekday() == weekday
+
+def compile(parsed):
+	ir = to_ir(parsed)
+	return to_lambda(ir)
diff --git a/lukkari/generate_timetable.py b/lukkari/generate_timetable.py
index b9bcc04..096e321 100644
--- a/lukkari/generate_timetable.py
+++ b/lukkari/generate_timetable.py
@@ -1,5 +1,4 @@
 import datetime
-from . import check_date
 
 def generate_timetable(day_range, courses):
 	start_date, end_date = day_range.range()
@@ -7,7 +6,7 @@ def generate_timetable(day_range, courses):
 	appointments = []
 	while True:
 		for name, info, date_filter in courses:
-			if check_date.check_day_match(date, date_filter):
+			if date_filter(date):
 				appointments.append((date, name, info))
 
 		if date == end_date: