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143 lines
3.5 KiB
Plaintext
143 lines
3.5 KiB
Plaintext
:: Little app to demonstrate the structure of programs written with the
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:: transaction monad.
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::
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:: Fetches the top comment of each of the top 10 stories from Hacker News
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::
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/+ tapp, stdio
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::
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:: Preamble
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::
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=>
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|%
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+$ state
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$: top-comments=(list tape)
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==
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+$ in-poke-data [%noun =cord]
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+$ out-poke-data ~
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+$ in-peer-data ~
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+$ out-peer-data
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$% [%comments (list tape)]
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==
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++ tapp (^tapp state in-poke-data out-poke-data in-peer-data out-peer-data)
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++ stdio (^stdio out-poke-data out-peer-data)
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--
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=>
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|%
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:: Helper function to print a comment
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::
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++ comment-to-tang
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|= =tape
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^- tang
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%+ welp
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%+ turn (rip 10 (crip tape))
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|= line=cord
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leaf+(trip line)
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[leaf+""]~
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::
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:: All the URLs we fetch from
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::
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++ urls
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=/ base "https://hacker-news.firebaseio.com/v0/"
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:* top-stories=(weld base "topstories.json")
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item=|=(item=@ud `tape`:(welp base "item/" +>:(scow %ui item) ".json"))
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==
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--
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=, async=async:tapp
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=, tapp-async=tapp-async:tapp
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=, stdio
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::
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:: The app
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::
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%- create-tapp-poke-peer-take:tapp
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^- tapp-core-poke-peer-take:tapp
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|_ [=bowl:gall state]
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::
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:: Main function
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::
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++ handle-poke
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|= =in-poke-data
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=/ m tapp-async
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^- form:m
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::
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:: If requested to print, just print what we have in our state
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::
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?: =(cord.in-poke-data 'print')
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~& 'drumroll please...'
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;< now=@da bind:m get-time
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;< ~ bind:m (wait (add now ~s3))
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~& 'Top comments:'
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%- (slog (zing (turn top-comments comment-to-tang)))
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(pure:m top-comments)
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?: =(cord.in-poke-data 'poll')
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;< ~ bind:m (wait-effect (add now.bowl ~s15))
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(pure:m top-comments)
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::
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:: Otherwise, fetch the top HN stories
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::
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=. top-comments ~
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::
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:: If this whole thing takes more than 15 seconds, cancel it
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::
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%+ (set-timeout _top-comments) (add now.bowl ~s15)
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;< =top-stories=json bind:m (fetch-json top-stories:urls)
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=/ top-stories=(list @ud)
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((ar ni):dejs:format top-stories-json)
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::
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:: Loop through the first 5 stories
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::
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=. top-stories (scag 5 top-stories)
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|- ^- form:m
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=* loop $
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::
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:: If done, tell subscribers and print the results
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::
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?~ top-stories
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;< ~ bind:m (give-result /comments %comments top-comments)
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(handle-poke %noun 'print')
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::
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:: Else, fetch the story info
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::
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~& "fetching item #{+>:(scow %ui i.top-stories)}"
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;< =story-info=json bind:m (fetch-json (item:urls i.top-stories))
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=/ story-comments=(unit (list @ud))
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((ot kids+(ar ni) ~):dejs-soft:format story-info-json)
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::
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:: If no comments, say so
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::
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?: |(?=(~ story-comments) ?=(~ u.story-comments))
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=. top-comments ["<no top comment>" top-comments]
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loop(top-stories t.top-stories)
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::
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:: Else, fetch comment info
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::
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;< =comment-info=json bind:m (fetch-json (item:urls i.u.story-comments))
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=/ comment-text=(unit tape)
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((ot text+sa ~):dejs-soft:format comment-info-json)
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::
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:: If no text (eg comment deleted), record that
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::
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?~ comment-text
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=. top-comments ["<top comment has no text>" top-comments]
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loop(top-stories t.top-stories)
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::
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:: Else, add text to state
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::
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=. top-comments [u.comment-text top-comments]
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loop(top-stories t.top-stories)
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::
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++ handle-peer
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|= =path
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=/ m tapp-async
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^- form:m
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~& [%tapp-fetch-take-peer path]
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(pure:m top-comments)
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::
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++ handle-take
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|= sign:tapp
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=/ m tapp-async
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^- form:m
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;< =state bind:m (handle-poke %noun 'fetch')
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=. top-comments state
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(pure:m top-comments)
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--
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