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381fa0f179
* feat: add semigroup instance for Env and Context Adds a semigroup instance for combining Envs and Contexts--this will be necessary to ensure closure's are evaluated under the combination of the context captured in the closure and the current global context during evaluation. The semigroup instances are left biased and will prefer bindings defined in the left context/env argument in the case of conflicts (this is in keeping with the implementation of `union` in Data.Map, the underlying function powering this instance). * fix: evaluate closures under the current context Previously, closures were evaluated only under the context that was stored during their creation. However, this can lead to issues where closures do not resolve bindings to their latest definitions. This commit leverages the semigroup instance of Context to evaluate closures under the combination of the context captured during their creation and the broader context during their evaluation/application, preferring the context captured in the closure when bindings conflict. This ensures that when we apply closures their local bindings still resolve to definitions encapsulated in the closure, while other bindings resolve to the definitions contained in the current overarching context (instead of the old context captured by the closure). * fix: fix bias for context env combinations in semigroup Previously, the semigroup instance for Context was left-biased in all the combinations of each context's environment. However, one usually calls this function to combine some older context with a newer context, intending to have the older context win *only* in the case of internal environments. This commit changes the behavior of the semigroup instance to better reflect this use case. When one calls: `c <> c'` The envs in each context are combined as follows: - internal: If conflicts occur, prefer the bindings of the context on the LHS (the "older" context) - global: If conflicts occur, prefer the bindings of the context on the RHS ("newer" context) - type: If conflicts occur, prefer the bindings of the context on the RHS ("newer" context) This ensures the resulting context uses the latest values in the chance of conflicts in the global env/type env, and the older values in the case of an internal env (a closure). * test: add basic tests for closures * refactor: rename test/closure -> test/dynamic-closure Also updates the forms to test dynamic closures.
59 lines
1.4 KiB
Plaintext
59 lines
1.4 KiB
Plaintext
(load "Test.carp")
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(use Test)
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(defdynamic x 400)
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;; close over a global variable
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(defdynamic closure-one
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(fn [] x))
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;; close over an argument
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(defdynamic closure-two
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(fn [x] x))
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;; close over a let binding
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(defdynamic closure-three
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(fn [] (let [x 4] x)))
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;; dynamics can close over a global variable before it is defined
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(defdynamic closure-four
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(fn [] y))
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;; nested closures prefer closed-over internal environments
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(defdynamic closure-five
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(fn [] (let [x 5] (fn [] x))))
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(defdynamic y 500)
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(defmacro test-closure-one [] (closure-one))
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(defmacro test-closure-two [] (closure-two 3))
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(defmacro test-closure-three [] (closure-three))
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(defmacro test-closure-four [] (closure-four))
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(defmacro test-closure-five [] ((closure-five)))
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;; Change the global value of x (closed over in closure-one)
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(set! x 1000)
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(deftest test
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(assert-equal test
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1000
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(test-closure-one)
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"closures over global variables get the global variable's latest state.")
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(assert-equal test
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3
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(test-closure-two)
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"closures with arguments use argument values")
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(assert-equal test
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4
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(test-closure-three)
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"closures with let bindings prefer let bindings over global names")
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(assert-equal test
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500
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(test-closure-four)
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"dynamic closures can refer to global bindings delcared after the closure")
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(assert-equal test
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5
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(test-closure-five)
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"nested closures prefer closed-over bindings")
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)
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