pratt

README

pratt

The pratt command is a stripped-down expression parser based on the Pratt parser. To help understand Pratt parsing, the command also provides a naive, recursive, right-associative expression parser and a naive, iterative, left-associative expression parser.

Try it with:

go run ./main.go '1 + 2 * 3'

Limitations

pratt is intended for demonstration and education purposes only. It is purposefully thin on error handling. The input expression is expected to be a valid, using known operators only: <, +, -, *, /. Operators and operands must be separated by a single space, e.g. 1 + 2 * 3.

svg command

The svg command is meant to be used with the pratt command. It generates and opens an SVG image of the expression tree in the default SVG viewer.

Try it with:

go install ./...
pratt '1 * 2 + 3 * 4' | svg -o

Installation

You can install the pratt command without cloning and rebuilding this repo.

Linux and Windows

Download the latest release for your platform, unzip it and add pratt to your path.

macOS

Use Homebrew to install pratt.

brew install evylang/tap/pratt