Working With The Dictionary

The Dictionary is a linked list containing the dictionary headers.

Namespace

Words operating on the dictionary are in the d: namespace.

Variables

Dictionary is a variable holding a pointer to the most recent header.

Header Structure

Each entry follows the following structure:

Offset   Contains ------   --------------------------- 0000     Link to Prior Header 0001     Link to XT 0002     Link to Class Handler 0003+    Word name (null terminated)

RETRO provides words for accessing the fields in a portable manner. It's recommended to use these to allow for future revision of the header structure.

Accessing Fields

Given a pointer to a header, you can use d:xt, d:class, and d:name to access the address of each specific field. There is no d:link, as the link will always be the first field.

Shortcuts For The Latest Header

RETRO provides several words for operating on the most recent header.

d:last returns a pointer to the latest header. d:last.xt will give the contents of the d:xt field for the latest header. There are also d:last.class and d:last.name.

Adding Headers

Two words exist for making new headers. The easy one is d:create. This takes a string for the name and makes a new header with the class set to class:data and the XT field pointing to here.

Example:

```
'Base d:create
```

The other is d:add-header. This takes a string, a pointer to the class handler, and a pointer for the XT field and builds a new header using these.

Example:

```
'Base &class:data #10000 d:add-header
```

Searching

RETRO provides two words for searching the dictionary.

d:lookup takes a string and tries to find it in the dictionary. It will return a pointer to the dictionary header or a value of zero if the word was not found.

d:lookup-xt takes a pointer and will return the dictionary header that has this as the d:xt field, or zero if no match is found.

Iteration

You can use the d:for-each combinator to iterate over all entries in the dictionary. For instance, to display the names of all words:

```
[ d:name s:put sp ] d:for-each
```

For each entry, this combinator will push a pointer to the entry to the stack and call the quotation.

Listing Words

Most Forth systems provide WORDS for listing the names of all words in the dictionary. RETRO does as well, but this is named d:words.

This isn't super useful as looking through several hundred names is annoying. RETRO also provides d:words-with to help in filtering the results.

Example:

```
'class: d:words-with
```