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[REBOL] Words, Bindings and Contexts. (6)

From: lmecir:geocities at: 24-Jul-2000 19:55

In the previous sections I answered some questions regarding Contexts. The lifetime Contexts: ************************* The Global Context should last forever, Local Context have indefinite extent, which should mean, that if there were no GC bugs, they should last as long, as they are accessible. Now something on Bindings: Bindings revealed: ********************** I think, that I succeeded to demonstrate, that every Rebol Word has got a Context attribute. The next attribute everybody is familiar with, is its Mold attribute. It is simply the value that can be obtained by: mold 'word The Context and Mold attributes are normally enough to characterize a Rebol Word. A special case can be discussed: Aliases. As a toy I present a function able to find out, if two given words are aliases of each other: aliases?: func [ {find out, if word1 and word2 are aliases} word1 [word!] word2 [word!] ] [ all [ ; aliases are equal in Rebol equal? word1 word2 ; but have different Mold attributes not equal? mold word1 mold word2 ] ] Aliases are not currently considered by Rebol as the same Words. (Because their Mold attributes differ?) Observation concerning Rebol Words is as follows: Two Words are the same, if their Context attributes are the same and their Mold attributes are equal. (This would be true probably for all Contexts, but we haven't got the means to check the case of Special Contexts and Dangerous Contexts.) Example illustrating, that the same value and equality of Words doesn't mean the same Binding: blk: copy [a] a: 11 b: make object! [append blk 'a a: 11] print [ mold blk ":" mold reduce blk ] print [ "Do the first and the second element above have the same Binding?" same-context? first blk second blk ] What I didn't discuss, is the case of recursive functions in Rebol, but I hope, that somebody finds even the present text helpful. (If any of the questions at the beginning remains unclear, feel free to ask.) Ladislav