diff options
author | Eduardo Julian | 2017-05-30 21:35:37 -0400 |
---|---|---|
committer | Eduardo Julian | 2017-05-30 21:35:37 -0400 |
commit | b73f1c909d19d5492d6d9a7dc707a3b817c73619 (patch) | |
tree | 369d957687852bb5ca0024e9175072f5c92bf6d1 /new-luxc/source/luxc/analyser/case.lux | |
parent | 56b0ca377a30e30bf832d6dfdb789676f67e7ade (diff) |
- Documented the analysis phase.
- Some refactoring.
- Removed singleton variants.
Diffstat (limited to 'new-luxc/source/luxc/analyser/case.lux')
-rw-r--r-- | new-luxc/source/luxc/analyser/case.lux | 294 |
1 files changed, 38 insertions, 256 deletions
diff --git a/new-luxc/source/luxc/analyser/case.lux b/new-luxc/source/luxc/analyser/case.lux index f3eec6b6b..306618caf 100644 --- a/new-luxc/source/luxc/analyser/case.lux +++ b/new-luxc/source/luxc/analyser/case.lux @@ -15,25 +15,25 @@ (macro [code]) [type] (type ["TC" check])) - (luxc ["&" base] - (lang ["la" analysis]) - ["&;" env] - (analyser ["&;" common] - ["&;" structure]))) - -(type: #rec Coverage - #PartialC - (#BoolC Bool) - (#VariantC Nat (D;Dict Nat Coverage)) - (#SeqC Coverage Coverage) - (#AltC Coverage Coverage) - #TotalC) + (../.. ["&" base] + (lang ["la" analysis]) + ["&;" env]) + (.. ["&;" common] + ["&;" structure]) + (. ["&&;" coverage])) (def: (pattern-error type pattern) (-> Type Code Text) (format "Cannot match this type: " (%type type) "\n" " With this pattern: " (%code pattern))) +## Type-checking on the input value is done during the analysis of a +## "case" expression, to ensure that the patterns being used make +## sense for the type of the input value. +## Sometimes, that input value is complex, by depending on +## type-variables or quantifications. +## This function makes it easier for "case" analysis to properly +## type-check the input with respect to the patterns. (def: (simplify-case-type type) (-> Type (Lux Type)) (case type @@ -60,6 +60,22 @@ _ (:: Monad<Lux> wrap type))) +## This function handles several concerns at once, but it must be that +## way because those concerns are interleaved when doing +## pattern-matching and they cannot be separated. +## The pattern is analysed in order to get a general feel for what is +## expected of the input value. This, in turn, informs the +## type-checking of the input. +## A kind of "continuation" value is passed around which signifies +## what needs to be done _after_ analysing a pattern. +## In general, this is done to analyse the "body" expression +## associated to a particular pattern _in the context of_ said +## pattern. +## The reason why *context* is important is because patterns may bind +## values to local variables, which may in turn be referenced in the +## body expressions. +## That is why the body must be analysed in the context of the +## pattern, and not separately. (def: (analyse-pattern num-tags inputT pattern next) (All [a] (-> (Maybe Nat) Type Code (Lux a) (Lux [la;Pattern a]))) (case pattern @@ -143,10 +159,10 @@ (&;fail (pattern-error inputT pattern)) ))) - [cursor (#;Record pairs)] + [cursor (#;Record record)] (do Monad<Lux> - [pairs (&structure;normalize-record pairs) - [members recordT] (&structure;order-record pairs) + [record (&structure;normalize record) + [members recordT] (&structure;order record) _ (&;within-type-env (TC;check inputT recordT))] (analyse-pattern (#;Some (list;size members)) inputT [cursor (#;Tuple members)] next)) @@ -200,240 +216,6 @@ (&;fail (format "Unrecognized pattern syntax: " (%code pattern))) )) -(def: (analyse-branch analyse inputT pattern body) - (-> &;Analyser Type Code Code (Lux [la;Pattern la;Analysis])) - (analyse-pattern #;None inputT pattern (analyse body))) - -(do-template [<name> <tag>] - [(def: (<name> coverage) - (-> Coverage Bool) - (case coverage - (<tag> _) - true - - _ - false))] - - [total? #TotalC] - [alt? #AltC] - ) - -(def: (determine-coverage pattern) - (-> la;Pattern Coverage) - (case pattern - (^or (#la;BindP _) (^ (#la;TupleP (list)))) - #TotalC - - (^ (#la;TupleP (list singleton))) - (determine-coverage singleton) - - (#la;BoolP value) - (#BoolC value) - - (^or (#la;NatP _) (#la;IntP _) (#la;DegP _) - (#la;RealP _) (#la;CharP _) (#la;TextP _)) - #PartialC - - (#la;TupleP subs) - (loop [subs subs] - (case subs - #;Nil - #TotalC - - (#;Cons sub subs') - (let [post (recur subs')] - (if (total? post) - (determine-coverage sub) - (#SeqC (determine-coverage sub) - post))))) - - (#la;VariantP tag-id num-tags sub) - (#VariantC num-tags - (|> (D;new number;Hash<Nat>) - (D;put tag-id (determine-coverage sub)))))) - -(def: (xor left right) - (-> Bool Bool Bool) - (or (and left (not right)) - (and (not left) right))) - -(def: redundant-pattern - (R;Result Coverage) - (R;fail "Redundant pattern.")) - -(def: (flatten-alt coverage) - (-> Coverage (List Coverage)) - (case coverage - (#AltC left right) - (list& left (flatten-alt right)) - - _ - (list coverage))) - -(struct: _ (Eq Coverage) - (def: (= reference sample) - (case [reference sample] - [#TotalC #TotalC] - true - - [(#BoolC sideR) (#BoolC sideS)] - (B/= sideR sideS) - - [(#VariantC allR casesR) (#VariantC allS casesS)] - (and (n.= allR allS) - (:: (D;Eq<Dict> =) = casesR casesS)) - - [(#SeqC leftR rightR) (#SeqC leftS rightS)] - (and (= leftR leftS) - (= rightR rightS)) - - [(#AltC _) (#AltC _)] - (let [flatR (flatten-alt reference) - flatS (flatten-alt sample)] - (and (n.= (list;size flatR) (list;size flatS)) - (list;every? (function [[coverageR coverageS]] - (= coverageR coverageS)) - (list;zip2 flatR flatS)))) - - _ - false))) - -(open Eq<Coverage> "C/") - -(def: (merge-coverages addition so-far) - (-> Coverage Coverage (R;Result Coverage)) - (case [addition so-far] - ## The addition cannot possibly improve the coverage. - [_ #TotalC] - redundant-pattern - - ## The addition completes the coverage. - [#TotalC _] - (R/wrap #TotalC) - - [#PartialC #PartialC] - (R/wrap #PartialC) - - (^multi [(#BoolC sideA) (#BoolC sideSF)] - (xor sideA sideSF)) - (R/wrap #TotalC) - - [(#VariantC allA casesA) (#VariantC allSF casesSF)] - (cond (not (n.= allSF allA)) - (R;fail "Variants do not match.") - - (:: (D;Eq<Dict> Eq<Coverage>) = casesSF casesA) - redundant-pattern - - ## else - (do R;Monad<Result> - [casesM (foldM @ - (function [[tagA coverageA] casesSF'] - (case (D;get tagA casesSF') - (#;Some coverageSF) - (do @ - [coverageM (merge-coverages coverageA coverageSF)] - (wrap (D;put tagA coverageM casesSF'))) - - #;None - (wrap (D;put tagA coverageA casesSF')))) - casesSF (D;entries casesA))] - (wrap (if (let [case-coverages (D;values casesM)] - (and (n.= allSF (list;size case-coverages)) - (list;every? total? case-coverages))) - #TotalC - (#VariantC allSF casesM))))) - - [(#SeqC leftA rightA) (#SeqC leftSF rightSF)] - (case [(C/= leftSF leftA) (C/= rightSF rightA)] - ## There is nothing the addition adds to the coverage. - [true true] - redundant-pattern - - ## The 2 sequences cannot possibly be merged. - [false false] - (R/wrap (#AltC so-far addition)) - - ## Same prefix - [true false] - (do R;Monad<Result> - [rightM (merge-coverages rightA rightSF)] - (if (total? rightM) - (wrap leftSF) - (wrap (#SeqC leftSF rightM)))) - - ## Same suffix - [false true] - (do R;Monad<Result> - [leftM (merge-coverages leftA leftSF)] - (wrap (#SeqC leftM rightA)))) - - ## The left part will always match, so the addition is redundant. - (^multi [(#SeqC left right) single] - (C/= left single)) - redundant-pattern - - ## The right part is not necessary, since it can always match the left. - (^multi [single (#SeqC left right)] - (C/= left single)) - (R/wrap single) - - [_ (#AltC leftS rightS)] - (do R;Monad<Result> - [#let [fuse-once (: (-> Coverage (List Coverage) - (R;Result [(Maybe Coverage) - (List Coverage)])) - (function [coverage possibilities] - (loop [alts possibilities] - (case alts - #;Nil - (wrap [#;None (list coverage)]) - - (#;Cons alt alts') - (case (merge-coverages coverage alt) - (#R;Success altM) - (case altM - (#AltC _) - (do @ - [[success alts+] (recur alts')] - (wrap [success (#;Cons alt alts+)])) - - _ - (wrap [(#;Some altM) alts'])) - - (#R;Error error) - (R;fail error)) - ))))] - [success possibilities] (fuse-once addition (flatten-alt so-far))] - (loop [success success - possibilities possibilities] - (case success - (#;Some coverage') - (do @ - [[success' possibilities'] (fuse-once coverage' possibilities)] - (recur success' possibilities')) - - #;None - (case (list;reverse possibilities) - #;Nil - (R;fail "{ This is not supposed to happen... }") - - (#;Cons last prevs) - (wrap (L/fold (function [left right] (#AltC left right)) - last - prevs)))))) - - _ - (if (C/= so-far addition) - ## The addition cannot possibly improve the coverage. - redundant-pattern - ## There are now 2 alternative paths. - (R/wrap (#AltC so-far addition))))) - -(def: get-coverage - (-> [la;Pattern la;Analysis] Coverage) - (|>. product;left determine-coverage)) - (def: #export (analyse-case analyse input branches) (-> &;Analyser Code (List [Code Code]) (Lux la;Analysis)) (case branches @@ -444,17 +226,17 @@ (do Monad<Lux> [[inputT inputA] (&common;with-unknown-type (analyse input)) - outputH (analyse-branch analyse inputT patternH bodyH) + outputH (analyse-pattern #;None inputT patternH (analyse bodyH)) outputT (mapM @ (function [[patternT bodyT]] - (analyse-branch analyse inputT patternT bodyT)) + (analyse-pattern #;None inputT patternT (analyse bodyT))) branchesT) _ (case (foldM R;Monad<Result> - merge-coverages - (get-coverage outputH) - (L/map get-coverage outputT)) + &&coverage;merge + (|> outputH product;left &&coverage;determine) + (L/map (|>. product;left &&coverage;determine) outputT)) (#R;Success coverage) - (if (total? coverage) + (if (&&coverage;total? coverage) (wrap []) (&;fail "Pattern-matching is not total.")) |