def first_expression(source):
"""Split string into (exp, rest) where exp is the
first expression in the string and rest is the
rest of the string after this expression."""
source = source.strip()
if source[0] == "'":
exp, rest = first_expression(source[1:])
return source[0] + exp, rest
elif source[0] == "(":
last = find_matching_paren(source)
return source[:last + 1], source[last + 1:]
else:
match = re.match(r"^[^\s)']+", source)
end = match.end()
atom = source[:end]
return atom, source[end:]
def first_expression(source):
"""Split string into (exp, rest) where exp is the
first expression in the string and rest is the
rest of the string after this expression."""
source = source.strip()
if source[0] == "'":
exp, rest = first_expression(source[1:])
return source[0] + exp, rest
elif source[0] == "(":
last = find_matching_paren(source)
return source[:last + 1], source[last + 1:]
else:
match = re.match(r"^[^\s)']+", source)
end = match.end()
atom = source[:end]
return atom, source[end:]
def test_find_matching_paren_throws_exception_on_no_closing_paren():
"""The function should raise error when there is no matching paren to be found"""
with assert_raises_regexp(LispError, "Incomplete expression"):
find_matching_paren("string (without closing paren", 7)
def test_find_matching_paren_throws_exception_on_bad_initial_position():
"""If asked to find closing paren from an index where there is no opening
paren, the function should raise an error"""
with assert_raises(AssertionError):
find_matching_paren("string without parens", 4)
def test_find_matching_empty_parens():
assert_equals(1, find_matching_paren("()", 0))
def test_find_matching_paren():
source = "(foo (bar) '(this ((is)) quoted))"
assert_equals(32, find_matching_paren(source, 0))
assert_equals(9, find_matching_paren(source, 5))
def test_find_matching_paren_throws_exception_on_no_closing_paren():
"""The function should raise error when there is no matching paren to be found"""
with assert_raises_regexp(LispError, "Incomplete expression"):
find_matching_paren("string (without closing paren", 7)
def test_find_matching_paren_throws_exception_on_bad_initial_position():
"""If asked to find closing paren from an index where there is no opening
paren, the function should raise an error"""
with assert_raises(AssertionError):
find_matching_paren("string without parens", 4)
def test_find_matching_empty_parens():
assert_equals(1, find_matching_paren("()", 0))
def test_find_matching_paren():
source = "(foo (bar) '(this ((is)) quoted))"
assert_equals(32, find_matching_paren(source, 0))
assert_equals(9, find_matching_paren(source, 5))