Mercurial > urweb
view tests/tags.ur @ 2123:1218daa14279
Document new infix operators
author | Adam Chlipala <adam@chlipala.net> |
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date | Thu, 05 Mar 2015 14:58:34 -0500 |
parents | 884673e5f7d5 |
children |
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table images : { Id : int, Content : blob } table tags : { Id : int, Tag : string } datatype mode = Present | Absent type condition = { Tag : string, Mode : mode } type tag_query = sql_query [] [] [] [Id = int] fun addCondition (c : condition) (q : tag_query) : tag_query = case c.Mode of Present => (SELECT I.Id AS Id FROM ({{q}}) AS I JOIN tags ON tags.Id = I.Id AND tags.Tag = {[c.Tag]}) | Absent => (SELECT I.Id AS Id FROM ({{q}}) AS I LEFT JOIN tags ON tags.Id = I.Id AND tags.Tag = {[c.Tag]} WHERE tags.Tag IS NULL) fun withConditions (cs : list condition) : tag_query = List.foldl addCondition (SELECT images.Id AS Id FROM images) cs fun main (cs : list condition) : transaction page = x <- queryX (withConditions cs) (fn r => <xml><li>{[r.Id]}</li></xml>); return <xml><body> {x} </body></xml>