PEGO Cookbook

Short recipes for concrete problems. Each one is a complete solution: the problem in a sentence or two, the grammar and the Go program, the output they print, and a few lines on how it works and what to change. They differ from the other documents in how they are organized:

• The tutorial teaches the language from the first rule on.
• The guides explain one feature at a time, in depth.
• The cookbook starts from a task (read a configuration file, report three errors at once, reparse on every keystroke) and combines the features that the task needs.

#Running a Recipe

Every program is a main package that you can run as it is. Put the files in a directory (a block whose first line is // name.go or // name.pego is a file of that name, without that line), make it a module that uses PEGO, and run it:

mkdir recipe && cd recipe
go mod init example.com/recipe
go get github.com/ornew/pego
go run .

The recipes need Go 1.27 or later and nothing else, except where a recipe says otherwise (the ones that generate code install the pego tool with go get -tool, and the one about ready-made parsers adds a module). The grammars are embedded in the programs with go:embed, so the .pego files are real files that pego fmt, pego parse and the editor support work with. Every output was produced by running the code shown, with Go 1.27.1 on an Apple M3 Max; times differ from machine to machine.

#Read Data

#Evaluate and Query

#Report Problems

#Build Tools

#Ship, Reuse and Test

#Where to Go Next