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require "./parcom/*"
module Parcom
VERSION = "0.1.0"
# A ParserFail exception should be raised by `Parser#parse` when
# a parse attempt is unsuccessful.
class ParserFail < Exception
end
# `Tokens` is an `Array` wrapper struct to store the input
# stream of one or more `Parser` objects.
# A `Tokens` can be created from any `Iterable`, along with
# `String` objects using a special constructor.
struct Tokens(T)
getter tokens
# Constructs a `Tokens(Char)` from a `String`.
def self.from_string(s : String) : Tokens(Char)
Tokens.new(s.chars)
end
# Constructs a `Tokens` from an `Iterable`.
def initialize(ts : Iterable(T))
if ts.responds_to?(:to_a)
@tokens = ts.to_a
else
@tokens = [] of T
ts.each { |t| @tokens << t }
end
end
# Exposes `Array#[](Int)`.
def [](index : Int) : T
@tokens[index]
end
# Exposes `Array#[](Int, Int)`, but wraps the returned array in a new `Tokens`.
def [](start : Int, count : Int) : Tokens(T)
Tokens.new(@tokens[start, count])
end
# Exposes `Array#[](Range)`, but wraps the returned array in a new `Tokens`.
def [](range : Range) : Tokens(T)
Tokens.new(@tokens[range])
end
# Like `#[]`, but returns `nil` instead of raising an `IndexError`.
def []?(*args)
self.[](*args)
rescue IndexError
nil
end
# Exposes `Array#empty?`.
def empty? : Bool
@tokens.empty?
end
end
# A `Result` stores a `Tokens` object and a parsed value,
# and is effectively used to store the state of a parser chain.
# This is used instead of a `Tuple` or `NamedTuple` because:
# 1. This is more idiomatic than a `Tuple`.
# 2. Crystal does not support generic named tuples.
struct Result(T, U)
getter tokens, value
def initialize(@tokens : Tokens(T), @value : U)
end
def map(f : U -> V) : Result(T, V) forall V
Result.new(@tokens, f.call(@value))
end
def map(&block : U -> V) : Result(T, V) forall V
map(block)
end
end
end
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