| paul@187 | 1 | Object contexts:
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| paul@187 | 2 |
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| paul@187 | 3 | Object Context
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| paul@187 | 4 | ------ -------
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| paul@187 | 5 | function overridable
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| paul@187 | 6 | method defining/originating class
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| paul@187 | 7 | class null
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| paul@187 | 8 | instance self
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| paul@187 | 9 | module null
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| paul@187 | 10 |
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| paul@186 | 11 | Assignment types:
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| paul@186 | 12 |
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| paul@186 | 13 | Assignment of stored value to... Effect on context
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| paul@186 | 14 | -------------------------------- -----------------
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| paul@186 | 15 | local preserved
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| paul@186 | 16 | global (module) preserved
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| paul@187 | 17 | class overridden (if overridable)
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| paul@186 | 18 | instance preserved
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| paul@186 | 19 |
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| paul@187 | 20 | Assignment to a namespace preserves the context except for some class
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| paul@187 | 21 | assignments
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| paul@187 | 22 |
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| paul@187 | 23 | Assigning to classes:
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| paul@187 | 24 |
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| paul@187 | 25 | Assignment of... Effect on context
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| paul@187 | 26 | ---------------- -----------------
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| paul@187 | 27 | function (overridable context) overridden by class (becomes method)
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| paul@187 | 28 | method (existing context) preserved
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| paul@187 | 29 | class (null context) preserved
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| paul@187 | 30 | instance (self context) preserved
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| paul@187 | 31 | module (null context) preserved
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| paul@187 | 32 |
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| paul@187 | 33 | With run-time restrictions on assignment targets:
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| paul@187 | 34 |
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| paul@187 | 35 | Assignment of stored value to... Effect on context Optimised instruction Unoptimised instruction
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| paul@187 | 36 | -------------------------------- ----------------- --------------------- -----------------------
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| paul@187 | 37 | local preserved StoreName
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| paul@187 | 38 | global (module) preserved StoreAddress StoreAttrIndex
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| paul@187 | 39 | instance preserved StoreAttr StoreAttrIndex
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| paul@223 | 40 | class -> class StoreAddressContext
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| paul@187 | 41 |
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| paul@223 | 42 | Class assignments are not permitted except during initialisation and hence
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| paul@223 | 43 | employ no unoptimised instruction
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| paul@186 | 44 |
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| paul@186 | 45 | Access types:
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| paul@186 | 46 |
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| paul@194 | 47 | Access to stored value from... Effect on context Optimised instruction Unoptimised instruction
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| paul@194 | 48 | ------------------------------ ----------------- --------------------- -----------------------
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| paul@186 | 49 | local preserved LoadName
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| paul@194 | 50 | global (module) preserved LoadAddress LoadAttrIndex
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| paul@194 | 51 | class preserved LoadAddress LoadAttrIndex
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| paul@223 | 52 | class via instance -> instance LoadAddressContext(Cond) LoadAttrIndexContext(Cond)
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| paul@194 | 53 | instance preserved LoadAttr LoadAttrIndex
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| paul@186 | 54 |
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| paul@186 | 55 | Access to a namespace may not preserve the stored context
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| paul@189 | 56 |
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| paul@189 | 57 | Access to class attributes via instances:
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| paul@189 | 58 |
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| paul@189 | 59 | Access to stored value with... Effect on context
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| paul@189 | 60 | ------------------------------ -----------------
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| paul@223 | 61 | compatible class as context -> instance
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| paul@189 | 62 | incompatible class as context preserved
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| paul@189 | 63 | null context preserved
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| paul@189 | 64 | other context (instance) preserved
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| paul@189 | 65 |
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| paul@194 | 66 | Optimisation possibilities for class attribute access via instances:
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| paul@193 | 67 |
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| paul@193 | 68 | Class Class attribute Context of attribute Instruction
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| paul@193 | 69 | ----- --------------- -------------------- -----------
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| paul@193 | 70 | known constant preserved LoadAddress
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| paul@223 | 71 | known constant -> instance LoadAddressContext
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| paul@194 | 72 | known not constant preserved LoadAddress (attribute may always be preserved)
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| paul@223 | 73 | known not constant -> instance LoadAddressContext (attribute may always be overridden)
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| paul@194 | 74 | known not constant not known LoadAddressContextCond (perform context check)
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| paul@194 | 75 | not known not known preserved LoadAttrIndex (attribute may have preserved context in all classes)
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| paul@223 | 76 | not known not known -> instance LoadAttrIndexContext (attribute may have overridden context in all classes)
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| paul@194 | 77 | not known not known not known LoadAttrIndexContextCond (perform context check for class attribute access)
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| paul@193 | 78 |
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| paul@189 | 79 | Since the object table encodes sufficient information (an instance must be
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| paul@189 | 80 | compatible to access the class attribute, and compatibility information is
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| paul@193 | 81 | stored), an explicit compatibility test may not always be required at
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| paul@193 | 82 | run-time
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