blob: 69543434205d79abab9f9b6ab925f5dbdc4e248a (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
|
module Liquid
class Parser
def initialize(input)
l = Lexer.new(input)
@tokens = l.tokenize
@p = 0 # pointer to current location
end
def jump(point)
@p = point
end
def consume(type = nil)
token = @tokens[@p]
if type && token[0] != type
raise SyntaxError, "Expected #{type} but found #{@tokens[@p].first}"
end
@p += 1
token[1]
end
# Only consumes the token if it matches the type
# Returns the token's contents if it was consumed
# or false otherwise.
def consume?(type)
token = @tokens[@p]
return false unless token && token[0] == type
@p += 1
token[1]
end
# Like consume? Except for an :id token of a certain name
def id?(str)
token = @tokens[@p]
return false unless token && token[0] == :id
return false unless token[1] == str
@p += 1
token[1]
end
def look(type, ahead = 0)
tok = @tokens[@p + ahead]
return false unless tok
tok[0] == type
end
def expression
token = @tokens[@p]
if token[0] == :id
variable_signature
elsif [:string, :number].include? token[0]
consume
elsif token.first == :open_round
consume
first = expression
consume(:dotdot)
last = expression
consume(:close_round)
"(#{first}..#{last})"
else
raise SyntaxError, "#{token} is not a valid expression"
end
end
def argument
str = ""
# might be a keyword argument (identifier: expression)
if look(:id) && look(:colon, 1)
str << consume << consume << ' '.freeze
end
str << expression
str
end
def variable_signature
str = consume(:id)
while look(:open_square)
str << consume
str << expression
str << consume(:close_square)
end
if look(:dot)
str << consume
str << variable_signature
end
str
end
end
end
|
