Initial

8 files changed, 382 insertions, 0 deletions

diff --git a/.editorconfig b/.editorconfig
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+root = true
+
+[*.cr]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true
diff --git a/.gitignore b/.gitignore
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+++ b/.gitignore
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+/docs/
+/lib/
+/bin/
+/.shards/
+*.dwarf
+
+# Libraries don't need dependency lock
+# Dependencies will be locked in applications that use them
+/shard.lock
diff --git a/LICENSE b/LICENSE
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+++ b/LICENSE
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+MIT License
+
+Copyright (c) 2023 Matthew Hall <hallmatthew314@gmail.com>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/README.md b/README.md
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+# parcom
+
+TODO: Write a description here
+
+## Installation
+
+1. Add the dependency to your `shard.yml`:
+
+   ```yaml
+   dependencies:
+     parcom:
+       github: your-github-user/parcom
+   ```
+
+2. Run `shards install`
+
+## Usage
+
+```crystal
+require "parcom"
+```
+
+TODO: Write usage instructions here
+
+## Development
+
+TODO: Write development instructions here
+
+## Contributing
+
+1. Fork it (<https://github.com/your-github-user/parcom/fork>)
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Add some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create a new Pull Request
+
+## Contributors
+
+- [Matthew Hall](https://github.com/your-github-user) - creator and maintainer
diff --git a/shard.yml b/shard.yml
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+++ b/shard.yml
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+name: parcom
+version: 0.1.0
+
+description: Simple parser combinator library
+
+authors:
+  - Matthew Hall <matthew@matthewhall.xyz>
+
+crystal: 1.7.2
+
+license: MIT
diff --git a/spec/parcom_spec.cr b/spec/parcom_spec.cr
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+++ b/spec/parcom_spec.cr
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+require "./spec_helper"
+
+require "../src/parcom.cr"
+
+include Parcom
+
+describe Result do
+  describe "#initialize" do
+    it "sets values for #tokens and #value" do
+      tokens = "esting".chars
+      value  = 't'
+      result = Result(Char, Char).new(tokens, value)
+
+      result.tokens.should eq(tokens)
+      result.value.should eq(value)
+    end
+  end
+end
+
+describe Parser do
+  describe "#|" do
+    it "creates an `Alt` instance from `self` and another `Parser(T, V)`" do
+      p = AnyToken(Char).new | AnyToken(Char).new
+
+      p.should be_a(Alt(Char, Char))
+    end
+  end
+
+  describe "#assert" do
+    it "creates an `Assert` instance from self and a `Proc(T, Bool)`" do
+      f = ->(x : Char) { x == '#' }
+      p = AnyToken(Char).new.assert(f)
+
+      p.should be_a(Assert(Char, Char))
+    end
+  end
+end
+
+describe Flunk do
+  describe "#parse" do
+    it "always fails" do
+      tokens = "testing".chars
+      expect_raises(ParserException) { Flunk(Char, Char).new.parse(tokens) }
+    end
+  end
+end
+
+describe AnyToken do
+  describe "#parse" do
+    it "succeeds when input is non-empty" do
+      tokens = "testing".chars
+      result = AnyToken(Char).new.parse(tokens)
+
+      result.tokens.should eq(tokens[1..])
+      result.value.should eq('t')
+    end
+
+    it "fails when input is empty" do
+      expect_raises(ParserException) { AnyToken(Char).new.parse([] of Char) }
+    end
+  end
+end
+
+describe Eof do
+  describe "#parse" do
+    it "succeeds when input is empty" do
+      result = Eof(Char).new.parse([] of Char)
+
+      result.tokens.empty?.should be_true
+      result.value.should be_nil
+    end
+
+    it "fails when input is non-empty" do
+      tokens = "testing".chars
+
+      expect_raises(ParserException) { Eof(Char).new.parse(tokens) }
+    end
+  end
+end
+
+describe Peek do
+  describe "#parse" do
+    it "does not modify the result of the wrapped parser" do
+      tokens = "testing".chars
+      parser = AnyToken(Char).new
+      result_normal = parser.parse(tokens)
+      result_peek = Peek.new(parser).parse(tokens)
+
+      result_peek.value.should eq(result_normal.value)
+    end
+
+    it "does not consume any input" do
+      tokens = "testing".chars
+      parser = AnyToken(Char).new
+      result = Peek.new(parser).parse(tokens)
+
+      result.tokens.should eq(tokens)
+    end
+  end
+end
+
+describe Assert do
+  describe "#parse" do
+    it "fails if the wrapped parser fails" do
+      test = ->(x : Char) { true } # doesn't matter for this test
+      p = Assert.new(AnyToken(Char).new, test)
+      expect_raises(ParserException) { p.parse([] of Char) }
+    end
+
+    it "fails if the result value fails the test" do
+      tokens = "testing".chars
+      test = ->(x : Char) { x == '$' }
+      p = Assert.new(AnyToken(Char).new, test)
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "succeeds if the wrapped parser succeeds and the test passes" do
+      tokens = "testing".chars
+      expected_char = tokens[0]
+      test = ->(x : Char) { x == expected_char }
+      p = Assert.new(AnyToken(Char).new, test)
+      result = p.parse(tokens)
+
+      result.value.should eq(expected_char)
+      test.call(expected_char).should be_true 
+    end
+  end
+end
+
+describe Satisfy do
+  describe "#parse" do
+    it "fails if there are input is empty" do
+      test = ->(x : Char) { x == '#' } # doesn't matter for this case
+      p = Satisfy(Char).new(test)
+
+      expect_raises(ParserException) { p.parse([] of Char) }
+    end
+
+    it "fails if the token fails the test" do
+      tokens = "testing".chars
+      test = ->(x : Char) { x == '#' }
+      p = Satisfy(Char).new(test)
+
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "succeeds if the token passes the test" do
+      tokens = "testing".chars
+      expected_char = tokens[0]
+      test = ->(x : Char) { x == expected_char }
+      p = Satisfy(Char).new(test)
+      result = p.parse(tokens)
+
+      result.value.should eq(expected_char)
+      test.call(result.value).should be_true
+    end
+  end
+end
+
+describe Token do
+  describe "#parse" do
+    it "fails if the input is empty" do
+      expect_raises(ParserException) { Token(Char).new('t').parse([] of Char) }
+    end
+
+    it "fails if the token is not the expected token" do
+      tokens = "testing".chars
+      p = Token(Char).new('#')
+
+      expect_raises(ParserException) { p.parse(tokens) }
+    end
+
+    it "succeeds if the token is the expected token" do
+      tokens = "testing".chars
+      expected_char = tokens[0]
+      p = Token(Char).new(expected_char)
+      result = p.parse(tokens)
+
+      result.value.should eq(expected_char)
+    end
+  end
+end
+
diff --git a/spec/spec_helper.cr b/spec/spec_helper.cr
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+++ b/spec/spec_helper.cr
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+require "spec"
+require "../src/parcom"
diff --git a/src/parcom.cr b/src/parcom.cr
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+++ b/src/parcom.cr
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+module Parcom
+  VERSION = "0.1.0"
+
+  class ParserException < Exception
+  end
+
+  class Result(T, V)
+    getter tokens, value
+
+    def initialize(@tokens : Array(T), @value : V)
+    end
+  end
+
+  abstract class Parser(T, V)
+    abstract def parse(tokens : Array(T)) : Result(T, V)
+
+    def assert(f : V -> Bool)
+      Assert.new(self, f)
+    end
+
+    def |(other : Parser(T, V)) : Parser(T, V)
+      Alt.new(self, other)
+    end
+  end
+
+  class Flunk(T, V) < Parser(T, V)
+    def parse(tokens) : Result(T, V)
+      raise ParserException.new("Flunk: parsing failed")
+    end
+  end
+
+  class AnyToken(T) < Parser(T, T)
+    def parse(tokens : Array(T)) : Result(T, T)
+      if tokens.empty?
+        raise ParserException.new("AnyToken: input was empty")
+      else
+        Result.new(tokens[1..], tokens[0])
+      end
+    end
+  end
+
+  class Eof(T) < Parser(T, Nil)
+    def parse(tokens : Array(T)) : Result(T, Nil)
+      if tokens.empty?
+        Result.new(tokens, nil)
+      else
+        raise ParserException.new("Eof: input was not empty")
+      end
+    end
+  end
+
+  class Peek(T, V) < Parser(T, V)
+    def initialize(@p : Parser(T, V))
+    end
+
+    def parse(tokens : Array(T)) : Result(T, V)
+      result = @p.parse(tokens)
+      Result.new(tokens, result.value)
+    end
+  end
+
+  class Assert(T, V) < Parser(T, V)
+    def initialize(@p : Parser(T, V), @f : V -> Bool)
+    end
+
+    def parse(tokens : Array(T)) : Result(T, V)
+      result = @p.parse(tokens)
+
+      unless @f.call(result.value)
+        raise ParserException.new("Assert: predicate failed")
+      end
+
+      result
+    end
+  end
+
+  class Satisfy(T) < Parser(T, T)
+    def initialize(@f : T -> Bool)
+    end
+
+    def parse(tokens : Array(T)) : Result(T, T)
+      AnyToken(T).new.assert(@f).parse(tokens)
+    end
+  end
+
+  class Token(T) < Parser(T, T)
+    def initialize(@expected : T)
+    end
+
+    def parse(tokens : Array(T)) : Result(T, T)
+      Satisfy(T).new(->(x : T) { x == @expected }).parse(tokens)
+    end
+  end
+
+  class Alt(T, V) < Parser(T, V)
+    def initialize(@p1 : Parser(T, V), @p2 : Parser(T, V))
+    end
+
+    def parse(tokens : Array(T)) : Result(T, V)
+      begin
+        @p1.parse(tokens)
+      rescue ParserException
+        @p2.parse(tokens)
+      end
+    end
+  end
+end
+