61 lines
1.3 KiB
Text
61 lines
1.3 KiB
Text
# Lexical Scope
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RETRO has a single dictionary, but does provide a means of using
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lexical scope to keep this dictionary clean.
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## Example
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```
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{{
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'A var
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:++A &A v:inc ;
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---reveal---
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:B ++A ++A @A n:put nl ;
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}}
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```
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In this example, the lexical namespace is created with `{{`. A
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variable (`A`) and word (`++A`) are defined. Then a marker is
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set with `---reveal---`. Another word (`B`) is defined, and the
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lexical area is closed with `}}`.
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The headers between `{{` and `---reveal---` are then hidden from
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the dictionary, leaving only the headers between `---reveal---`
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and `}}` exposed.
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If you wish to hide all headers in a `{{` ... `}}` block, leave
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out the `---reveal---`.
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```
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{{
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:a #3 ;
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:b a dup * ;
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}}
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```
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## Notes
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This only affects word visibility within the scoped area. As an
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example:
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```
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:a #1 ;
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{{
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:a #2 ;
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---reveal---
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:b 'a s:evaluate n:put ;
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}}
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```
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In this, after `}}` closes the area, the `:a #2 ;` is hidden and
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the `s:evaluate` will find the `:a #1 ;` when `b` is run.
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## A Word of Warning
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Use of these words can result in a corrupt dictionary and system
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crashes. Specifically, use of `---reveal---` with an empty private
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or public section will result in dictionary corruption.
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If you don't need private words, don't put them in a scope. And if
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you don't need public words, don't include the `---reveal---`.
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