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Using EquaSets in methods, take 2
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| // This is from github ScalaTest master, not in any release: | |
| // Here's a method that takes a general one. This method asks the passed EquaSet | |
| // for its enclosing EquaSets, and stores it in variable path. It then "copies" | |
| // the passed EquaSet into the new path, after which it can union with a newly | |
| // created EquaSet at the same path and return it. | |
| scala> def addBippy(set: EquaSets[String]#EquaSet): EquaSets[String]#EquaSet = { | |
| | val path = set.enclosingEquaSets | |
| | val relocated = set.copyInto(path) | |
| | relocated union path.EquaSet("bippy") | |
| | } | |
| addBippy: (set: org.scalactic.EquaSets[String]#EquaSet)org.scalactic.EquaSets[String]#EquaSet | |
| // Two EquaSets, not in scope in the above method | |
| scala> val lowered = SortedEquaSets[String](StringNormalizations.lowerCased.toOrderingEquality) | |
| lowered: org.scalactic.SortedEquaSets[String] = org.scalactic.SortedEquaSets@76640885 | |
| scala> val trimmed = EquaSets[String](StringNormalizations.trimmed.toHashingEquality) | |
| trimmed: org.scalactic.EquaSets[String] = org.scalactic.EquaSets@f4080ae | |
| // Can pass either kind to the method, because it is general | |
| scala> val lowBip = addBippy(lowered.EquaSet("Hi")) | |
| lowBip: org.scalactic.EquaSets[String]#EquaSet = EquaSet(Hi, bippy) | |
| scala> val trimBip = addBippy(trimmed.EquaSet("Hi")) | |
| trimBip: org.scalactic.EquaSets[String]#EquaSet = EquaSet(Hi, bippy) | |
| // Can't union the returned value, because it too is general | |
| scala> lowBip union lowered.EquaSet("ug") | |
| <console>:20: error: type mismatch; | |
| found : lowered.EquaSet | |
| required: _8.EquaSet where val _8: org.scalactic.EquaSets[String] | |
| lowBip union lowered.EquaSet("ug") | |
| ^ | |
| // But once "copied" into the desired path, it can be unioned | |
| scala> lowBip.copyInto(lowered) union lowered.EquaSet("ug") | |
| res3: lowered.EquaSet = EquaSet(Hi, bippy, ug) | |
| // The reason I put copied in scare quotes is that copyInto has an optimization | |
| // that if it is the same instance, it just casts it to the new type. So it is | |
| // really relocating the same object to the new path. | |
| scala> lowBip eq lowBip.copyInto(lowered) | |
| res4: Boolean = true | |
| scala> trimBip.copyInto(lowered) union trimmed.EquaSet("ug") | |
| <console>:21: error: type mismatch; | |
| found : trimmed.EquaSet | |
| required: lowered.EquaSet | |
| trimBip.copyInto(lowered) union trimmed.EquaSet("ug") | |
| ^ | |
| // Can do the same stuff with trimmed | |
| scala> trimBip.copyInto(trimmed) union trimmed.EquaSet("ug") | |
| res6: trimmed.EquaSet = EquaSet(Hi, bippy, ug) | |
| scala> trimBip eq trimBip.copyInto(trimmed) | |
| res7: Boolean = true | |
| // Can also copy into a different path, in which case it is of course | |
| // a real copy--i.e., a new EquaSet instance | |
| scala> trimBip eq trimBip.copyInto(lowered) | |
| res8: Boolean = false | |
| scala> trimBip.copyInto(lowered) union lowered.EquaSet("ug") | |
| res9: lowered.EquaSet = EquaSet(Hi, bippy, ug) | |
| // And you still get the desired type errors if you try to mix notions | |
| // of equality used to determine set membership | |
| scala> trimBip.copyInto(lowered) union trimmed.EquaSet("ug") | |
| <console>:21: error: type mismatch; | |
| found : trimmed.EquaSet | |
| required: lowered.EquaSet | |
| trimBip.copyInto(lowered) union trimmed.EquaSet("ug") | |
| ^ | |
| // I made enclosingEquaSets a stable identifier so you could do the following. | |
| // I think I'll just rename enclosingEquaSets to path to make this kind | |
| // of usage more concise. | |
| scala> def addBoppy(set: EquaSets[String]#EquaSet): EquaSets[String]#EquaSet = { | |
| | val relocated = set.copyInto(set.enclosingEquaSets) | |
| | relocated union set.enclosingEquaSets.EquaSet("bippy") | |
| | } | |
| addBoppy: (set: org.scalactic.EquaSets[String]#EquaSet)org.scalactic.EquaSets[String]#EquaSet | |
| // I believe this is the approach you were talking about. That's actually pretty | |
| // clean looking. I think I can explain it in examples: | |
| scala> def addBeppy(sets: EquaSets[String])(set: sets.EquaSet): sets.EquaSet = { | |
| | set union sets.EquaSet("bippy") | |
| | } | |
| addBoppy: (sets: org.scalactic.EquaSets[String])(set: sets.EquaSet)sets.EquaSet | |
| scala> lowered.EquaSet("hi") union addBeppy(lowered)(lowered.EquaSet("ha")) | |
| res14: lowered.EquaSet = EquaSet(hi, ha, bippy) | |
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