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Add low-level iteration with for expression #106

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Jul 19, 2012
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Add low-level iteration with for expression #106

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2 changes: 2 additions & 0 deletions cheatsheets/index.md
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Expand Up @@ -57,6 +57,8 @@ about: Thanks to <a href="http://brenocon.com/">Brendan O'Connor</a>, this cheat
| `for ((x,y) <- xs zip ys) yield x*y` _same as_ <br>`(xs zip ys) map { case (x,y) => x*y }` | for comprehension: destructuring bind |
| `for (x <- xs; y <- ys) yield x*y` _same as_ <br>`xs flatMap {x => ys map {y => x*y}}` | for comprehension: cross product |
| `for (x <- xs; y <- ys) {`<br> `println("%d/%d = %.1f".format(x,y, x*y))`<br>`}` | for comprehension: imperative-ish<br>[sprintf-style](http://java.sun.com/javase/6/docs/api/java/util/Formatter.html#syntax) |
| `for (i <- 1 to 5) {`<br> `println(i)`<br>`}` | for comprehension: iterate including the upper bound |
| `for (i <- 1 until 5) {`<br> `println(i)`<br>`}` | for comprehension: iterate omitting the upper bound |
| <h2 id="pattern_matching">pattern matching</h2> | |
| <span class="label success">Good</span> `(xs zip ys) map { case (x,y) => x*y }`<br> <span class="label important">Bad</span> `(xs zip ys) map( (x,y) => x*y )` | use case in function args for pattern matching. |
| <span class="label important">Bad</span><br>`val v42 = 42`<br>`Some(3) match {`<br>` case Some(v42) => println("42")`<br>` case _ => println("Not 42")`<br>`}` | "v42" is interpreted as a name matching any Int value, and "42" is printed. |
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