Make the line continuation lazy. (#10)

This pull-request makes the continuation of the line lazy, and performance improves drastically.
bkase · Jun 28, 2018 · d481eee · d481eee
1 parent 7e1b0fe
commit d481eee
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Showing 3 changed files with 14 additions and 4 deletions.
diff --git a/Sources/DoctorPretty/RenderPretty.swift b/Sources/DoctorPretty/RenderPretty.swift
@@ -44,7 +44,7 @@ extension Doc {
             // This parameter is only used during annotation, but I'm
             // keeping it here to simplify adding the annotation case
             // in doc if that ever happens
-            z: (IndentLevel, ColumnCount) -> SimpleDoc,
+            z: @escaping (IndentLevel, ColumnCount) -> SimpleDoc,
             indentationDocs: Docs
         ) -> SimpleDoc {
             switch indentationDocs {
@@ -62,7 +62,7 @@ extension Doc {
                     let newColumn = currColumn + length
                     return SimpleDoc.text(length: length, str, best(currNesting: currNesting, currColumn: newColumn, z: z, indentationDocs: rest))
                 case ._line:
-                    return SimpleDoc.line(indent: indent, best(currNesting: indent, currColumn: indent, z: z, indentationDocs: rest))
+                    return SimpleDoc.line(indent: indent, { best(currNesting: indent, currColumn: indent, z: z, indentationDocs: rest) })
                 case let .flatAlt(primary, whenFlattened: _):
                     return best(currNesting: currNesting, currColumn: currColumn, z: z, indentationDocs: .Cons((indent, primary), rest))
                 case let .concat(d1, d2):

diff --git a/Sources/DoctorPretty/SimpleDoc.swift b/Sources/DoctorPretty/SimpleDoc.swift
@@ -16,15 +16,15 @@ public indirect enum SimpleDoc {
     case empty
     case char(Character, SimpleDoc)
     case text(length: Int, String, SimpleDoc)
-    case line(indent: Int, SimpleDoc)
+    case line(indent: Int, () -> SimpleDoc)
 
     public func display<M: Additive>(readString: (String) -> M) -> M {
         switch self {
         case .empty: return M.zero
         case let .char(c, rest): return readString(String(c)) <> rest.display(readString: readString)
         case let .text(_, s, rest): return readString(s) <> rest.display(readString: readString)
         case let .line(indent, rest):
-            return readString("\n" + spaces(indent)) <> rest.display(readString: readString)
+            return readString("\n" + spaces(indent)) <> rest().display(readString: readString)
         }
     }
 

diff --git a/Tests/DoctorPrettyTests/DoctorPrettyTests.swift b/Tests/DoctorPrettyTests/DoctorPrettyTests.swift
@@ -4,6 +4,16 @@ import Operadics
 
 // Most tests ported from https://github.com/minad/wl-pprint-annotated/blob/master/test/WLPPrintTests.hs
 class DoctorPrettyTests: XCTestCase {
+
+    func testSlow() {
+        measure {
+            let doc = (1...30).map { _ in
+                (1...30).map { _ in "foo" }.map(Doc.text).fillSep()
+                }.vcat()
+            _ = doc.renderPrettyDefault()
+        }
+    }
+
     func assertPretty(pageWidth: Width, str: String, doc: Doc, file: StaticString = #file, line: UInt = #line) {
         XCTAssertEqual(doc.renderPretty(ribbonFrac: 1.0, pageWidth: pageWidth).displayString(), str, file: file, line: line)
     }