Merge pull request #51 from dvanhorn/next

Next

www/Makefile

@@ -15,9 +15,9 @@ $(course):
 		++xref-in setup/xref load-collections-xref \
 		--redirect-main http://docs.racket-lang.org/ \
 		$(course).scrbl
-	mkdir -p $(course)/code/
+	mkdir -p $(course)/code/	
 	cd notes ; \
-		tar -c `git ls-files -X .gitignore intro abscond blackmail con dupe extort fraud hustle iniquity jig knock loot mug` | \
+		tar -c `git ls-files -X .gitignore intro abscond blackmail con dupe extort fraud hustle iniquity jig knock loot mug fp project.pdf` | \
 		(cd ../main/code ; tar -x) ; cd ../..
 
 clean:

www/info.rkt

@@ -0,0 +1,2 @@
+#lang info
+(define test-omit-paths '("notes/fp/sieve.rkt"))

www/notes/fp/sieve.rkt

@@ -0,0 +1,127 @@
+#lang racket
+
+(begin
+  ;; sieve for computing primes, based on GT Benchmarks
+
+  ;;--------------------------------------------------------------------------------------------------
+  ;; streams
+
+  (define (stream hd thunk)
+    (cons hd thunk))
+
+  (define (stream-first s)
+    (car s))
+
+  (define (stream-rest s)
+    (cdr s))
+
+  ;(: make-stream (-> Natural (-> stream) stream))
+  (define (make-stream hd thunk)
+    (stream hd thunk))
+
+  ;; Destruct a stream into its first value and the new stream produced by de-thunking the tail
+  ;(: stream-unfold (-> stream (cons Natural stream)))
+  (define (stream-unfold st)
+    (cons (stream-first st) ((stream-rest st))))
+
+  ;; [stream-get st i] Get the [i]-th element from the stream [st]
+  ;(: stream-get (-> stream Natural Natural))
+  (define (stream-get st i)
+    (match (stream-unfold st)
+      [(cons hd tl) 
+       (cond [(= i 0) hd]
+             [else    (stream-get tl (sub1 i))])]))
+
+  ;; [stream-take st n] Collect the first [n] elements of the stream [st].
+  ;(: stream-take (-> stream Natural (Listof Natural)))
+  (define (stream-take st n)
+    (cond [(= n 0) '()]
+          [else (match (stream-unfold st)
+                  [(cons hd tl)
+                   (cons hd (stream-take tl (sub1 n)))])]))
+
+  ;;--------------------------------------------------------------------------------------------------
+  ;; sieve
+
+  ;; `count-from n` Build a stream of integers starting from `n` and iteratively adding 1
+  ;(: count-from (-> Natural stream))
+  (define (count-from n)
+    (make-stream n (λ () (count-from (add1 n)))))
+
+  ;; `sift n st` Filter all elements in `st` that are equal to `n`.
+  ;; Return a new stream.
+  ;(: sift (-> Natural stream stream))
+  (define (sift n st)
+    (match (stream-unfold st)
+      [(cons hd tl)  
+       (cond [(= 0 (modulo hd n)) (sift n tl)]
+             [else (make-stream hd (λ () (sift n tl)))])]))
+
+  ;; `sieve st` Sieve of Eratosthenes
+  ;(: sieve (-> stream stream))
+  (define (sieve st)
+    (match (stream-unfold st)
+      [(cons hd tl) 
+       (make-stream hd (λ () (sieve (sift hd tl))))]))
+
+  ;; stream of prime numbers
+  ;(: primes (-> stream)
+  (define (primes) (sieve (count-from 2)))
+
+  ;;--------------------------------------------------------------------------------------------------
+  ;; reading numbers
+
+  (define (* n m)
+    (match n
+      [0 0]
+      [1 m]
+      [n (+ m (* (sub1 n) m))]))
+
+  (define (expt n m)
+    (match m
+      [0 1]
+      [1 n]
+      [m (* n (expt n (sub1 m)))]))
+
+  (define (read-number)
+    (digits->number (read-digits)))
+
+  (define (read-digits)
+    (let ((c (read-char)))
+      (if (eof-object? c)
+          '()
+          (if (eq? #\newline c)
+              '()
+              (cons c (read-digits))))))
+
+  (define (digits->number ds)
+    (match ds
+      ['() 0]
+      [(cons d ds)
+       (+ (* (digit->number d)
+             (expt 10 (length ds)))
+          (digits->number ds))]))
+
+  (define (digit->number d)
+    (match d
+      [#\0 0]
+      [#\1 1]
+      [#\2 2]
+      [#\3 3]
+      [#\4 4]
+      [#\5 5]
+      [#\6 6]
+      [#\7 7]
+      [#\8 8]
+      [#\9 9]))
+
+  ;;--------------------------------------------------------------------------------------------------
+  (define (modulo n m)
+    (if (< n m)
+        n
+        (modulo (- n m) m)))
+
+  ;;--------------------------------------------------------------------------------------------------
+  ;; computes nth prim
+
+  (stream-get (primes) (sub1 (read-number))))

www/project.scrbl

@@ -1,6 +1,6 @@
 #lang scribble/manual
 @(require "defns.rkt")
-@title[#:style '(toc unnumbered)]{Project}
+@title[#:style '(unnumbered)]{Project}
 
 There will be a final course project to be completed over the last
 several weeks of the course.  The project will involve extending the
@@ -19,6 +19,8 @@ learned over the semester to complete a full-featured compiler.
 Project repository:
 @centered{@link[repo repo]}
 
+@link["code/project.pdf"]{Slides} from lecture on the project.
+
 You are given a working compiler for an extension of the language we
 have been developing all semester.
 
@@ -62,6 +64,38 @@ in the compiler.
 There will be a garbage collector provided by the second round of
 benchmarks which you will need to incorporate in to your compiler.
 
+@section[#:tag-prefix "fp-" #:style 'unnumbered]{Measuring run-times}
+
+Let's look at an example of how to measure the run-time performance of
+the code your compiler generates.
+
+First, let's start with fairly computationally intensive program.
+Here is a @link["code/fp/sieve.rkt"]{program} that computes the
+@emph{n}th prime number using the ancient
+@link["https://en.wikipedia.org/wiki/Sieve_of_Eratosthenes"]{Sieve of
+Eratosthenes} method.
+
+Save it to the directory where your compiler lives and run @tt{make
+sieve.run}.  This will run the compiler to generate the @tt{sieve.run}
+executable.  This program expects to read a number from the standard
+input port.
+
+Run:
+
+@centered{@tt{echo -n 100 | ./sieve.run}}
+
+to compute the 100th prime number.
+
+To measure the time it takes, add the time command:
+
+@centered{@tt{echo -n 100 | time ./sieve.run}}
+
+This will run the program and show the result @emph{and} timing
+information.  We will be concerned with improving the real time it
+takes to run the program.
+
+
+@section[#:tag-prefix "fp-" #:style 'unnumbered]{Testing}
 
 @bold{There is separate a repository for tests.} When you push your
 code, Travis will automatically run your code against the tests.  If