1 / 8

CS 341 Programming Language Design and Implementation

CS 341 Programming Language Design and Implementation. Administrative HW #6 is released — due Monday 3/3 @ 11am (class start) image processing in F# Today? Winding down our discussion of functional programming Anyone for curry? most recent HW and Quiz. Function parameters == tuples

yestin
Download Presentation

CS 341 Programming Language Design and Implementation

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CS 341 Programming Language Design and Implementation • Administrative • HW #6 is released — due Monday 3/3 @ 11am (class start) • image processing in F# • Today? • Winding down our discussion of functional programming • Anyone for curry? • most recent HW and Quiz CS 341 -- 21 Feb 2014

  2. Function parameters == tuples • parameters in F# are not what you think… Not 2 parameters, but 1 tuple let add2(x, y) = x + y let result = add2(10, 20) printf"add2: %A\n" add2(10, 20) let add2 (x, y) = x + y let result = add2 (10, 20) printf"add2: %A\n" (add2(10, 20)) X Error: compiler sees 3 args to printf Correct: 2 argsto printf CS 341 -- 21 Feb 2014

  3. Declaring functions in F# • Two ways to declare — and the calls must match! • tupled: more traditional syntax with ( ) • curried: more flexible approach without ( ) letadd2(x, y) = x + y // tupled: val add2 : int * int -> int letR1 = add2(10, 20) // call with ( ) printfn "%A" R1 // 30 let add2cx y = x + y // curried: val add2c : int -> int -> int let R2 = add2c 10 20 // call without ( ) printfn "%A" R2 // 30 CS 341 -- 21 Feb 2014

  4. Def: a function is curried if you can supply fewer arguments — in which case the function is not called, but a new function is returned instead. Curried? • What does that mean? • And more importantly, why? • more flexible — allows you to use functions in situations where 1 or more arguments are supplied later… let add x y = x + y let R = add 10 20 let incr= add 1 add: int-> int -> int R: int incr: int -> int CS 341 -- 21 Feb 2014

  5. Real example? • Computing standard deviation… part of standard deviation computation let DiffSquared m x = Math.Pow(x-m, 2.0) let stddev(values) = let N = length(values) let mean = sum(values) / float(N) let diffs = List.map (DiffSquared mean) values Math.Sqrt( sum(diffs) / float(N) ) CS 341 -- 21 Feb 2014

  6. F# convention: • Most functions are defined in curried form without ( ) • and so we don't use ( ) when we call them… let add x y = x + y let R1 = add 10 20 let L2 = List.map (add 1) L printfn"%A, %A" R1 L2 CS 341 -- 21 Feb 2014

  7. Homework 5 • Lots of ways to solve, I used 4 lists -> 2 lists -> 1 list 100 60 90 . . [100; 60; 90; …] 90 80 90 . . [90; 80; 90; …] [ weighted scores ] 22 60 90 . . [22; 60; 90; …] [ final scores ] 100 100 100 . . [22; 60; 90; …] [ weighted scores ] CS 341 -- 21 Feb 2014

  8. Quiz 2 • Worse than expected… • Average: 66 • High: 100 • Low: 5 CS 341 -- 21 Feb 2014

More Related