Flagon

An ASCII graph parser written in Go. Flagon stands for FLuid ASCII Graph Object Notation.

Table of Contents

• Flagon
  • Table of Contents
  • Installation
  • Quick Start
  • Examples
    • Parsing an ASCII Graph
    • Getting Nodes
    • Getting Edges
    • Traversing a Graph
  • Testing
  • Acknowledgments

Installation

Run this command from your Go project directory to add Flagon to your project's go.mod file:

go get github.com/PappasBrent/flagon

Quick Start

Import Flagon:

import "github.com/PappasBrent/flagon"

Assign a string variable to the ASCII graph you would like to Flagon to parse:

text := `[A]-AB-[B]
         |
         AC
         |
         [C]
`

Parse the string variable with a call to the Parse function:

graph, _ := flagon.Parse(text)

Unnecessary labels for nodes and edges can be omitted, e.g., this is valid:

text := `[A]-AB-[B]
         |
         |
         []
`

Examples

Parsing an ASCII Graph

text := `[A]-AB-[B]
         |
         |
         []
`

graph, _ := flagon.Parse(text)

Getting Nodes

Graph structs have a LabeledNodes field containing a mapping of all labels to their corresponding Node structs. Labels are strings.

Example:

  text := `[A]-AB-[B]
           |
           |
           []
`

    graph, _ := flagon.Parse(text)
    for label, node := range graph.LabeledNodes {
        fmt.Printf("Parsed a node with label %v on line %v"+
          " with left bracket at column %v\n",
          label, node.Line, node.LeftColumn)
    }

Output:

Parsed a node with label A on line 1 with left bracket at column 1
Parsed a node with label B on line 1 with left bracket at column 8

All of a graph's nodes are stored in its Nodes field. Continuing from the previous example:

  for _, node := range graph.Nodes {
    fmt.Printf("Parsed a node starting at line %v column %v\n",
      node.Line, node.LeftColumn)
  }

Output:

Parsed a node starting at line 1 column 1
Parsed a node starting at line 1 column 8
Parsed a node starting at line 4 column 14

Getting Edges

Graph structs have a LabeledEdges field containing a mapping of all labels to their corresponding Edge structs. Labels are strings.

Example:

  for label, edge := range graph.LabeledEdges {
    fmt.Printf("Parsed an edge with label %v with top-left at"+
      " %v:%v and bottom-right at %v:%v\n", label, edge.TopLine,
      edge.LeftColumn, edge.BottomLine, edge.RightColumn)
  }

Output:

Parsed an edge with label AB with top-left at 1:4 and bottom-right at 1:7

All of a graph's edges are stored in its Edges field. Continuing from the previous example:

  for _, edge := range graph.Edges {
    fmt.Printf("Parsed an edge with top-left at"+
      " %v:%v and bottom-right at %v:%v\n", edge.TopLine,
      edge.LeftColumn, edge.BottomLine, edge.RightColumn)
  }

Output:

Parsed an edge with top-left at 1:4 and bottom-right at 1:7
Parsed an edge with top-left at 2:14 and bottom-right at 3:14

Traversing a Graph

Testing

Use go test to run Flagon's tests.

To run the tokenization tests use go test ./tokenization

Parser tests have not yet been implemented. Use go test ./parser to run the parser tests once they have been added.

Acknowledgments

• The Funciton esoteric programming language for the idea
• This research paper for suggestions on the implementation: Tomita M. (1991) Parsing 2-Dimensional Language. In: Tomita M. (eds) Current Issues in Parsing Technology. The Springer International Series in Engineering and Computer Science (Natural Language Processing and Machine Translation), vol 126. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-3986-5_18