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@@ -5,7 +5,8 @@
APIs and all other packages are subject to change in future
releases.
Be sure to read doc/jargon.txt and the description below.
+ href=#package_description>description below; there is also a
+ faq a the end of this document.
+I get the error java.lang.Error: multiple non-dropped elements + in sequence, what does this mean? +
+ ++Note: this question deals with the +package edu.berkeley.sbp.meta, which is not considered +stable. +
+ ++When using the class edu.berkeley.sbp.meta.Grammar, you must +supply an instance of Grammar.Bindings; this instance tells +SBP how to create a parse tree for an expression using the parse trees +of its subexpressions. +
+ ++SBP has no trouble determining what to do when parsing an expression +that drops all of its subexpressions, or all but one -- for example: +
+ ++... in this example, only C is "non-dropped". In this case, +the result of parsing A is simply the result of parsing +C. +
+ ++However, if we were to leave more than one element un-dropped, SBP +needs to know how to form a single tree out of the two non-dropped +subtrees. There are two ways to do this. The simplest is to provide +a tag -- a string which becomes the common parent of the two subtrees: +
+ ++If you are using AnnotationGrammarBindings, you can also deal +with this situation by declaring a method/inner-class whose name +matches the nonterminal (Expr) and has appropriate +annotations. This is fairly advanced stuff, and the code it uses +isn't quite as mature as the rest of the code. +
+ +