beautiful-racket/beautiful-racket-demo/precalc-demo/grammar.rkt

#lang brag

top : (func-def | func-app)*
func-def : /"fun" var /"(" vars /")" /"=" expr
/vars : [var (/"," var)*]
@expr : sum
sum : [sum ("+" | "-")] product
product : [product ("*" | "/")] value
@value : var | INT | func-app | /"(" expr /")"
func-app : var /"(" [expr (/"," expr)*] /")"
@var : ID