Is there a difference between Forth vocabularies and word lists?

Question

As I read "Programming Forth" by Stephen Pelc, the text seems to imply that vocabularies and word lists may be separate things. I have thought that dictionary vocabulary entries have a name field, code field, etc. so having separate word lists does not make sense to me.

Are word lists just a way of talking about the name fields of Forth words or are word lists actual data structures separate from dictionary entries? (Forth language resources are a bit scarce compared to mainstream languages)

Answer 1

Vocabularies and wordlists are basically the same. I can think of two differences:

• Wordlists are specified in the Forth standard. Vocabularies are not, but there's nearly a consensus on how they are used.
• A vocabulary has a name. A wordlist just has a numeric id.

A third similar concept is a "lexicon". I haven't seen it used as often as the other two, but I think it's yet another variation or a synonym.

A wordlist is a collection of dictionary entries. It could be a linked list, a hash table, or anything else that works for looking up named entries. The dictionary may be partitioned into several wordlists, i.e. a wordlist is a subset of the dictionary.

Answer 2

A wordlist is the ISO 94 Forth standard name of what is generally called a namespace. wikipedia does a good job in explaining this concept. In Forth multiple namespaces can be coupled to the interpreter which means that words in it can be used, and coupling a namespaces is called "adding the wordlist to the search order". Forth is extensible and has the pretty unique feature that new additions may be added to any wordlist, even one that is not in the search order. That namespace is called CURRENT and the actual, momentaneous search order, consisting of one or more namespaces, is called the CONTEXT. Both can be changed anywhere in an interactive session and anywhere in a compilation.

At the time of creation of the standard there was no consensus of how to give a name to a wordlist, so there is only the word WORDLIST that creates an anonymous namespace and leaves its handle on the stack. The word VOCABULARY was widely in use to create a named namespace, but because there was no consensus about it, VOCABULARY is not part of the standard and one cannot use it in portable programs (which is quite cumbersome, so everybody does it anyway and hopes for the best.)

So to summarize. wordlist as a concept is a namespace. WORDLIST creates an anonymous wordslist and is a standard word. VOCABULARY is not a standard word, mostly it will create a wordlist and couple a name and behaviour to it.