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diff --git a/go/golang/go/doc/codewalk/functions.xml b/go/golang/go/doc/codewalk/functions.xml new file mode 100644 index 00000000..db518dcc --- /dev/null +++ b/go/golang/go/doc/codewalk/functions.xml @@ -0,0 +1,105 @@ +<codewalk title="First-Class Functions in Go"> + +<step title="Introduction" src="doc/codewalk/pig.go"> + Go supports first class functions, higher-order functions, user-defined + function types, function literals, closures, and multiple return values. + <br/><br/> + + This rich feature set supports a functional programming style in a strongly + typed language. + <br/><br/> + + In this codewalk we will look at a simple program that simulates a dice game + called <a href="http://en.wikipedia.org/wiki/Pig_(dice)">Pig</a> and evaluates + basic strategies. +</step> + +<step title="Game overview" src="doc/codewalk/pig.go:/\/\/ A score/,/thisTurn int\n}/"> + Pig is a two-player game played with a 6-sided die. Each turn, you may roll or stay. + <ul> + <li> If you roll a 1, you lose all points for your turn and play passes to + your opponent. Any other roll adds its value to your turn score. </li> + <li> If you stay, your turn score is added to your total score, and play passes + to your opponent. </li> + </ul> + + The first person to reach 100 total points wins. + <br/><br/> + + The <code>score</code> type stores the scores of the current and opposing + players, in addition to the points accumulated during the current turn. +</step> + +<step title="User-defined function types" src="doc/codewalk/pig.go:/\/\/ An action/,/bool\)/"> + In Go, functions can be passed around just like any other value. A function's + type signature describes the types of its arguments and return values. + <br/><br/> + + The <code>action</code> type is a function that takes a <code>score</code> + and returns the resulting <code>score</code> and whether the current turn is + over. + <br/><br/> + + If the turn is over, the <code>player</code> and <code>opponent</code> fields + in the resulting <code>score</code> should be swapped, as it is now the other player's + turn. +</step> + +<step title="Multiple return values" src="doc/codewalk/pig.go:/\/\/ roll returns/,/true\n}/"> + Go functions can return multiple values. + <br/><br/> + + The functions <code>roll</code> and <code>stay</code> each return a pair of + values. They also match the <code>action</code> type signature. These + <code>action</code> functions define the rules of Pig. +</step> + +<step title="Higher-order functions" src="doc/codewalk/pig.go:/\/\/ A strategy/,/action\n/"> + A function can use other functions as arguments and return values. + <br/><br/> + + A <code>strategy</code> is a function that takes a <code>score</code> as input + and returns an <code>action</code> to perform. <br/> + (Remember, an <code>action</code> is itself a function.) +</step> + +<step title="Function literals and closures" src="doc/codewalk/pig.go:/return func/,/return roll\n\t}/"> + Anonymous functions can be declared in Go, as in this example. Function + literals are closures: they inherit the scope of the function in which they + are declared. + <br/><br/> + + One basic strategy in Pig is to continue rolling until you have accumulated at + least k points in a turn, and then stay. The argument <code>k</code> is + enclosed by this function literal, which matches the <code>strategy</code> type + signature. +</step> + +<step title="Simulating games" src="doc/codewalk/pig.go:/\/\/ play/,/currentPlayer\n}/"> + We simulate a game of Pig by calling an <code>action</code> to update the + <code>score</code> until one player reaches 100 points. Each + <code>action</code> is selected by calling the <code>strategy</code> function + associated with the current player. +</step> + +<step title="Simulating a tournament" src="doc/codewalk/pig.go:/\/\/ roundRobin/,/gamesPerStrategy\n}/"> + The <code>roundRobin</code> function simulates a tournament and tallies wins. + Each strategy plays each other strategy <code>gamesPerSeries</code> times. +</step> + +<step title="Variadic function declarations" src="doc/codewalk/pig.go:/\/\/ ratioS/,/string {/"> + Variadic functions like <code>ratioString</code> take a variable number of + arguments. These arguments are available as a slice inside the function. +</step> + +<step title="Simulation results" src="doc/codewalk/pig.go:/func main/,/\n}/"> + The <code>main</code> function defines 100 basic strategies, simulates a round + robin tournament, and then prints the win/loss record of each strategy. + <br/><br/> + + Among these strategies, staying at 25 is best, but the <a + href="http://www.google.com/search?q=optimal+play+pig">optimal strategy for + Pig</a> is much more complex. +</step> + +</codewalk> |