streams are interesting

lib/stream_functions.js

@@ -0,0 +1,44 @@
+StreamFunctions = function(features) {
+  var terminator = features.eof || {}
+  var functionsForExport = {}
+
+  function eof(thing) {
+    return thing === terminator
+  }
+  functionsForExport.eof = eof
+
+
+  function detect(stream, matcher) {
+    var candidate = null
+    while (!eof(candidate=stream.next())) {
+      if (matcher(candidate)) return candidate
+    }
+    return terminator
+  }
+  functionsForExport.detect = detect
+  // 
+  // function select(iterator, matcher) {
+  //   return {
+  //     var empty = {}
+  //     var nextMatch == features.nothing()
+  //     
+  //     function advanceIfNecessary() {
+  //       if (nextMatch === empty) nextMatch = detect(iterator, matcher)
+  //       return nextMatch
+  //     }
+  //     
+  //     hasNext: function() {
+  //       return !(advanceIfNecessary() === terminator)
+  //     },
+  //     next: function() {
+  //       if (!hasNext()) throw "after end"
+  //       var result = advanceIfNecessary()
+  //       nextMatch = empty
+  //       return result
+  //     }
+  //   }
+  // }
+  // functionsForExport.select = select
+
+  return {functions:functionsForExport}    
+}

spec/stream/detect_spec.js

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+require("./spec_helper.js");
+
+describe("detect", function() {
+
+  var f = StreamFunctions({eof:EOF}).functions
+
+  it("finds the next occurrence in a stream and then stops", function(){
+    var stream = arrayStream([1,2,3,4,5,6])
+    expect(f.detect(stream, function(item){return item %2==0})).toEqual(2)
+    expect(f.detect(stream, function(item){return item %2==0})).toEqual(4)
+    expect(f.detect(stream, function(item){return item %2==0})).toEqual(6)    
+    expect(f.eof(f.detect(stream, function(item){return item %2==0}))).toEqual(true)
+  })
+
+  it("returns eof if there's no match", function(){
+    var stream = arrayStream([1,2,3,4,5,6])
+    var result = f.detect(stream, function(item){return item == 99})
+    expect(f.eof(result)).toEqual(true)
+  })
+
+})
+

spec/stream/spec_helper.js

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+require.paths.push("spec")
+require.paths.push("lib")
+
+require("../../../jasmine-node/lib/jasmine")
+
+for(var key in jasmine) {
+  global[key] = jasmine[key]
+}
+
+require("stream_functions")
+
+EOF = "THIS IS THE END"
+
+arrayStream = function(arr) {
+  var position = 0
+  return {
+    next: function() {
+      if (position == arr.length) {
+        return EOF
+      } else {
+        var result = arr[position]
+        position += 1
+        return result
+      }
+    }
+  }
+}

spec/stream/suite.js

@@ -0,0 +1,3 @@
+require("./spec_helper")
+
+jasmine.requireAllSpecFiles(__dirname)