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Meta-language for DSL implementation inspired by Xtext

Project description

https://raw.githubusercontent.com/textX/textX/master/art/textX-logo.png

PyPI Version license build-status Documentation Status

textX is a meta-language for building Domain-Specific Languages (DSLs) in Python. It is inspired by Xtext.

In a nutshell, textX will help you build your textual language in an easy way. You can invent your own language or build a support for already existing textual language or file format.

From a single language description (grammar), textX will build a parser and a meta-model (a.k.a. abstract syntax) for the language. See the docs for the details.

textX follows the syntax and semantics of Xtext but differs in some places and is implemented 100% in Python using Arpeggio PEG parser - no grammar ambiguities, unlimited lookahead, interpreter style of work.

Quick intro

Here is a complete example that shows the definition of a simple DSL for drawing. We also show how to define a custom class, interpret models and search for instances of a particular type.

from textx import metamodel_from_str, get_children_of_type

grammar = """
Model: commands*=DrawCommand;
DrawCommand: MoveCommand | ShapeCommand;
ShapeCommand: LineTo | Circle;
MoveCommand: MoveTo | MoveBy;
MoveTo: 'move' 'to' position=Point;
MoveBy: 'move' 'by' vector=Point;
Circle: 'circle' radius=INT;
LineTo: 'line' 'to' point=Point;
Point: x=INT ',' y=INT;
"""

# We will provide our class for Point.
# Classes for other rules will be dynamically generated.
class Point(object):
    def __init__(self, parent, x, y):
        self.parent = parent
        self.x = x
        self.y = y

    def __str__(self):
        return "{},{}".format(self.x, self.y)

    def __add__(self, other):
        return Point(self.parent, self.x + other.x, self.y + other.y)

# Create meta-model from the grammar. Provide `Point` class to be used for
# the rule `Point` from the grammar.
mm = metamodel_from_str(grammar, classes=[Point])

model_str = """
    move to 5, 10
    line to 10, 10
    line to 20, 20
    move by 5, -7
    circle 10
    line to 10, 10
"""

# Meta-model knows how to parse and instantiate models.
model = mm.model_from_str(model_str)

# At this point model is a plain Python object graph with instances of
# dynamically created classes and attributes following the grammar.

def cname(o):
    return o.__class__.__name__

# Let's interpret the model
position = Point(None, 0, 0)
for command in model.commands:
    if cname(command) == 'MoveTo':
        print('Moving to position', command.position)
        position = command.position
    elif cname(command) == 'MoveBy':
        position = position + command.vector
        print('Moving by', command.vector, 'to a new position', position)
    elif cname(command) == 'Circle':
        print('Drawing circle at', position, 'with radius', command.radius)
    else:
        print('Drawing line from', position, 'to', command.point)
        position = command.point
print('End position is', position)

# Output:
# Moving to position 5,10
# Drawing line from 5,10 to 10,10
# Drawing line from 10,10 to 20,20
# Moving by 5,-7 to a new position 25,13
# Drawing circle at 25,13 with radius 10
# Drawing line from 25,13 to 10,10

# Collect all points starting from the root of the model
points = get_children_of_type("Point", model)
for point in points:
    print('Point: {}'.format(point))

# Output:
# Point: 5,10
# Point: 10,10
# Point: 20,20
# Point: 5,-7
# Point: 10,10

Video tutorials

Introduction to textX

https://img.youtube.com/vi/CN2IVtInapo/0.jpg

Implementing Martin Fowler’s State Machine DSL in textX

https://img.youtube.com/vi/HI14jk0JIR0/0.jpg

Docs and tutorials

The full documentation with tutorials is available at http://textx.github.io/textX/stable/

Support in IDE/editors

Discussion and help

For general questions and help please use StackOverflow. Just make sure to tag your question with the textx tag.

For issues, suggestions and feature request please use GitHub issue tracker.

License

MIT

Python versions

Tested for 2.7, 3.4+

Project details


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