65 lines
1.4 KiB
Forth
65 lines
1.4 KiB
Forth
# Sandboxed Dictionaries
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This implements some words to create a sandboxed dictionary and
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to execute a word or quotation within the sandbox.
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# Making A Sandboxed Dictionary
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The dictionary is structured as a linked list. To make a new one,
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I take an array with the names from the global dictionary, extract
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the header fields for each, and make a new list using them.
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The `make-dict` will return a pointer to the last entry in the new
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dictionary.
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~~~
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{{
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'D var
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:unpack (d-saa)
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d:lookup [ d:name ] [ d:class fetch ] [ d:xt fetch ] tri ;
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:add-header (saa-)
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here [ @D , , , s, ] dip !D ;
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---reveal---
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:make-dict (a-a)
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#0 !D [ unpack add-header ] array:for-each @D ;
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}}
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~~~
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The `{ ... } make-dict` can be wrapped in something to make this
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a little more obvious.
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~~~
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:dict{ (-) |{ ; immediate
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:}dict (-a) |} |make-dict ; immediate
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~~~
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# Using The Sandboxed Dictionary
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I implement a very simple `d:with` to run a quote with a
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sandboxed dictionary. This works by temporarily replacing
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the global dictionary with the sandboxed one.
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~~~
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:d:with (qa-)
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&Dictionary [ !Dictionary call ] v:preserve ;
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~~~
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# A Test Case
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This will expose a dictionary with just two words that can be
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used with a new `%` prefix.
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```
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{{
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:swap $A ;
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:dup $B ;
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dict{ 'swap 'dup }dict 'SANDBOX const
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---reveal---
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:prefix:% (s) [ s:evaluate c:put ] SANDBOX d:with ;
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}}
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#70 dup swap
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%swap %dup
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n:put n:put
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nl bye
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```
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