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preprocess.llrl
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preprocess.llrl
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(import "std/hash-map" _)
(import "std/hash-set" _)
(import "~/util" _)
(import "~/sexp" _)
(import "~/source-location" SourceLocation _.SourceLocation)
(import "~/preprocess/error" Error _.Error error:_)
(export Error _.Error error:_)
(export Preprocessor _.Preprocessor preprocessor/_)
(function META_PREFIX "$")
; A preprocessor that processes directives in S-expressions.
; The preprocessor is executed before semantic analysis.
(derive (DebugDisplay Default) value-data Preprocessor
(preprocessor: (HashSet String)))
(getter preprocessor: enabled-features)
(function (preprocessor/new) {(-> Preprocessor)}
default)
(function (preprocessor/enable-feature! feature pp) {(-> String Preprocessor unit)}
(ignore (hash-set/insert! feature (enabled-features pp))))
(function (preprocessor/run pp ss) {(forall A) (-> Preprocessor (Ss A) (Result (Ss A) Error))}
@with1 (ss: (let loc) (let elems)) ss
@let1 buf vector/empty
@let1 (put! s) (ok (vector/push! s buf))
@let1 state (state: pp hash-map/empty)
(for (let s) elems (expand! state put! s)!)
(ok (ss: loc (vector/buffer buf))))
(data (State A)
(state: Preprocessor (HashMap String (S A))))
(getter state: pp vars)
(function (expand-one! state place s)
{(forall A) (-> (State A) String (S A) (Result (S A) Error))}
@let1 buf (ref (err #f))
@let1 (put! s) (ok (set! buf (if-match1 (err #f) ~buf (ok s) (err #t))))
(expand! state put! s)!
(result/map-err [^1 (error:expansion-disallowed (s/location s) place)] ~buf))
(function (expand! state put! s)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) (S A) (Result unit Error))}
@let1 loc (s/location s)
(match s
[(s*symbol (let sym))
(if (string/starts-with? META_PREFIX sym)
(if-match1 (some (let s)) (hash-map/get? sym (vars state))
(put! s)
(err (error:undefined-meta-variable loc sym)))
(put! s))]
[(s*cons (let car) (let cdr))
(if-match (
[#t (s/proper-list? cdr)]
[(s*symbol (let sym)) car]
[(some (let directive)) (conv sym)])
(handle-directive! state put! loc directive cdr)
(begin
@let1 init vector/empty
@let1 last (expand-elems! state [^1 (ok (vector/push! %1 init))] s)!
(put! (it/fold [^2 (s: loc (s-rep:cons %2 %1))] last (rev-iterate init)))))]
[_
(put! s)]))
; Traverse list elements and expand them.
(function (expand-elems! state put! s)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) (S A) (Result (S A) Error))}
@let1 tail (ref s)
(while-match1 (s*cons (let car) (let cdr)) ~tail
(expand! state put! car)!
(set! tail cdr))
; If s is not a proper list, this function returns non-nil.
(expand-one! state "cdr of cons cell" ~tail))
(function (handle-directive! state put! loc directive args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation Directive (S A) (Result unit Error))}
(match directive
[directive:symbol (handle-symbol-directive! state put! loc args)]
[directive:let (handle-let-directive! state put! loc args)]
[directive:let1 (handle-let1-directive! state put! loc args)]
[directive:for (handle-for-directive! state put! loc args)]
[directive:for1 (handle-for1-directive! state put! loc args)]
[directive:when (handle-when-directive! state put! loc args)]
[directive:not (handle-not-directive! state put! loc args)]
[directive:feature (handle-feature-directive! state put! loc args)]))
(function (handle-symbol-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
@let1 name text/empty
@let1 (put-component! s)
(match s
[(s*symbol (let s)) (ok (text/push! s name))]
[(s*string (let s)) (ok (text/push! s name))]
[(s*char (let c)) (ok (text/put! c name))]
[_ (err (error:directive-syntax loc "($symbol <symbol or string or char>...)"))])
(expand-elems! state put-component! args)!
(if (text/empty? name)
(err (error:empty-symbol loc))
(put! (s: loc (s-rep:symbol (text/consume-all! name))))))
(function (handle-let-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match1 (s*list-like (let binds) (let body)) args
@when (s/proper-list? binds)
@let1 expanded-binds vector/empty
(for (let bind) (cars binds)
(if-match (
[(s*list (s*symbol (let name)) (let expr)) bind]
[#t (metavar? name)])
(let1 expr (expand-one! state "$let bind expression" expr)!
(vector/push! (: name expr) expanded-binds))
(err (error:directive-syntax (s/location bind) "[$var <expr>]"))!))
(with-binds! state expanded-binds [^0 (expand-elems! state put! body)])!
(return (ok unit)))
(err (error:directive-syntax loc "($let ([$var <expr>]...) <body>...)")))
(function (handle-let1-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match1 (s*list-like (s*symbol (let name)) (let expr) (let body)) args
@when (metavar? name)
@let1 expr (expand-one! state "$let1 expression" expr)!
(with-binds! state (iterator/only (: name expr)) [^0 (expand-elems! state put! body)])!
(return (ok unit)))
(err (error:directive-syntax loc "($let1 $var <expr> <body>...)")))
(function (handle-for-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match1 (s*list-like (let s-names) (let s-elemss) (let body)) args
@when (s/proper-list? s-names)
@let1 s-elemss (expand-one! state "$for elements" s-elemss)!
@when (s/proper-list? s-elemss)
@let1 names vector/empty
@let1 elemss vector/empty
(for (let s-name) (cars s-names)
(if-match (
[(s*symbol (let name)) s-name]
[#t (metavar? name)])
(vector/push! name names)
(err (error:directive-syntax (s/location s-name) "$var"))!))
(for (let s-elems) (cars s-elemss)
@let1 elems (|> s-elems cars collect)
(if (and (s/proper-list? s-elems) (eq? (vector/length names) (array/length elems)))
(vector/push! elems elemss)
(err (error:directive-syntax (s/location s-elems) "[<elem>...]"))!))
(for (let elems) elemss
(with-binds! state (it/zip names elems) [^0 (expand-elems! state put! body)])!)
(return (ok unit)))
(err (error:directive-syntax loc "($for [$var...] ([<elem>...]...) <body>...)")))
(function (handle-for1-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match1 (s*list-like (s*symbol (let name)) (let elems) (let body)) args
@when (metavar? name)
@let1 elems (expand-one! state "$for1 elements" elems)!
@when (s/proper-list? elems)
(for (let elem) (cars elems)
(with-binds! state (iterator/only (: name elem)) [^0 (expand-elems! state put! body)])!)
(return (ok unit)))
(err (error:directive-syntax loc "($for1 $var (<elem>...) <body>...)")))
(function (handle-when-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match (
[(s*list-like (let cond) (let body)) args]
[(s*bool (let value)) (expand-one! state "$when condition" cond)!])
(when value (expand-elems! state put! body)!)
(return (ok unit)))
(err (error:directive-syntax loc "($when <bool> <body>...)")))
(function (handle-not-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match (
[(s*list (let cond)) args]
[(s*bool (let value)) (expand-one! state "$not condition" cond)!])
(put! (s: loc (s-rep:bool (not value))))!
(return (ok unit)))
(err (error:directive-syntax loc "($not <bool>)")))
(function (handle-feature-directive! state put! loc args)
{(forall A) (-> (State A) (-> (S A) (Result unit Error)) SourceLocation (S A) (Result unit Error))}
(when-match (
[(s*list (let feature)) args]
[(s*string (let feature)) (expand-one! state "$feature string" feature)!])
@let1 value (hash-set/has? feature (|> state pp enabled-features))
(put! (s: loc (s-rep:bool value)))!
(return (ok unit)))
(err (error:directive-syntax loc "($feature <string>)")))
(function (with-binds! state binds f)
{(forall T A R) (-> (State A) (T (: String (S A))) (-> R) R) (where (Iterate T))}
@let1 vars (vars state)
@let1 prev-binds {(Vector (: String (Option (S A))))}
(|> binds
(it/filter @case1 (: (let name) _) (ne? name "_"))
(it/map @case1 (: (let name) (let expr)) (: name (hash-map/insert! name expr vars)))
collect)
@let1 result (f)
(for (: (let name) (let prev-expr)) prev-binds
(if-match1 (some (let prev-expr)) prev-expr
(hash-map/insert! name prev-expr vars)
(hash-map/remove! name vars)))
result)
(derive (Eq DebugDisplay) value-data Directive
directive:symbol
directive:let
directive:let1
directive:for
directive:for1
directive:when
directive:not
directive:feature)
(instance Conv.From.Symbol.To.Directive (Conv String (Option Directive))
(function (conv sym)
(match? sym
["$symbol" directive:symbol]
["$let" directive:let]
["$let1" directive:let1]
["$for" directive:for]
["$for1" directive:for1]
["$when" directive:when]
["$not" directive:not]
["$feature" directive:feature])))
(function (metavar? sym) {(-> String Bool)}
(or (string/starts-with? META_PREFIX sym) (eq? sym "_")))
(function (cars s) {(forall A) (-> (S A) (Iterator (S A)))}
(iterator/unfold (case1? (s*cons (let car) (let cdr)) (: car cdr)) s))