プログラミング学習の記録 345.2「『Programming F#』 Chris Smith 著のⅠ部(マルチパラダイムプログラミング), 3章(関数プログラミング), 1(関数によるプログラミング)の1(不変性), 2(関数値)

開発環境

• Microsoft Windows 7 Home Premium (OS)
• Microsoft Visual Studio 2010(Visual Studio 2010 Shell + F# Community Technology Preview(CTP)(F# Compiler and F# for Visual Studio)) (IDE)
• 言語: F# (A Functional Programming Langage)

「『Programming F#』 Chris Smith 著、Copyright 2010 Chris Smith、ISBN 978-9-596-15364-9、邦題『プログラミング F#』 オライリー・ジャパン刊、ISBN 978-4-87311-466-8」のⅠ部(マルチパラダイムプログラミング)、3章(関数プログラミング)を参考に学習。3.1(関数によるプログラミング)の3.1.1(不変性), 3.1.2(関数値)の3.1.2.1(関数の部分適用), 3.1.2.2(関数を返す関数)まで。

FSI(F# Interactive)

Microsoft (R) F# 2.0 Interactive build 4.0.30319.1 Copyright (c) Microsoft Corporation. All Rights Reserved. For help type #help;; > let f x=x**2.0+x let g x=x+1.0;; val f : float -> float val g : float -> float > f 10.0;; val it : float = 110.0 > g 10.0;; val it : float = 11.0 > f (g 10.0);; val it : float = 132.0 > let square x=x*x;; val square : int -> int > let imperativeSum numbers= let mutable total=0 for i in numbers do let x=square i total <- total + x total;; val imperativeSum : seq<int> -> int > let functionalSumnumbers= numbers |> Seq.map square |> Seq.sum;; numbers ----^^^^^^^ stdin(14,5): error FS0039: The value or constructor 'numbers' is not defined > let functionalSum numbers= numbers |> Seq.map square |> Seq.sum;; val functionalSum : seq<int> -> int > imperativeSum 10;; imperativeSum 10;; --------------^^ stdin(21,15): error FS0001: The type 'int' is not compatible with the type 'seq<int>' > imperativeSum [1 ... 10];; imperativeSum [1 ... 10];; --------------------^ stdin(22,21): error FS0010: Unexpected symbol '.' in expression > imperativeSum [1 .. 10];; val it : int = 385 > functionalSum [1 .. 10];; val it : int = 385 > let negte x=-x;; let negte x=-x;; -----------^^ stdin(25,12): error FS0010: Unexpected infix operator in binding. Expected '=' or other token. > let negate x = -x;; val negate : int -> int > List.map negate [1 .. 10];; val it : int list = [-1; -2; -3; -4; -5; -6; -7; -8; -9; -10] > (fun x -> x + 3) 5;; val it : int = 8 > ( fun x -> x**2) 10;; ( fun x -> x**2) 10;; -----------------^^ stdin(29,18): error FS0001: The type 'int' does not support any operators named 'Pow' > (fun x -> x**2) 10.0;; (fun x -> x**2) 10.0;; ----------------^^^^ stdin(30,17): error FS0001: The type 'int' does not match the type 'float' > (fun x -> x**2.0) 10.0;; val it : float = 100.0 > List.map ( fun i -> -i) [1 .. 10];; val it : int list = [-1; -2; -3; -4; -5; -6; -7; -8; -9; -10] > List.map ( fun x -> pow 2 x) [ 1 .. 10];; List.map ( fun x -> pow 2 x) [ 1 .. 10];; ---------------------^^^ stdin(33,22): error FS0039: The value or constructor 'pow' is not defined > List.map ( fun x -> pown 2 x) [1 .. 10];; val it : int list = [2; 4; 8; 16; 32; 64; 128; 256; 512; 1024] > open system.IO let appendFile (fileName : string) (text : string)= use file = new StremWriter(fileName, true) file.WriteLine(text) file.Close();; open system.IO -----^^^^^^ stdin(35,6): error FS0039: The namespace or module 'system' is not defined > open System.IO let appendFile (fileName : string) (text : string)= use file = new StreamWriter(fileName, true) file.WriteLine(text) file.Close();; val appendFile : string -> string -> unit > appendFile @"C:\Users\Kamimura\Documents\Log.txt" "Test";; val it : unit = () > // appendFileをカリー化 let curriedAppendFile = appendFile @"C:\Users\Kamimura\Documents\Log.txt";; val curriedAppendFile : (string -> unit) > curriedAppendFile "カリー化した関数をTest";; val it : unit = () > List.iter ( fun i -> printfn "%d" i) [1 .. 3];; 1 2 3 val it : unit = () > List.iter (printfn "%d") [1 .. 3];; 1 2 3 val it : unit = () > // まだいまいち良く分かってない let generatePowerOfFunc baseValue = (fun exponent -> (pown baseValue exponent);; let generatePowerOfFunc baseValue = (fun exponent -> (pown baseValue exponent);; ------------------------------------------------------------------------------^^ stdin(54,79): error FS0010: Incomplete structured construct at or before this point in expression. Expected ')' or other token. > let generatePowerOfFunc baseValue = (fun exponent -> pown baseValue exponent);; val generatePowerOfFunc : int -> int -> int > let powerOfTwo = generatePowerOfFunc 2.0;; let powerOfTwo = generatePowerOfFunc 2.0;; -------------------------------------^^^ stdin(56,38): error FS0001: This expression was expected to have type int but here has type float > let generatePowerOfFunc baseValue = (fun exponent -> baseValue ** exponent);; val generatePowerOfFunc : float -> float -> float > let powerOfTwo = generatePowerOfFunc 2.0;; val powerOfTwo : (float -> float) > powerOfTwo 10.0;; val it : float = 1024.0 > let powerOfThree = generatePowerOfFunc 3.0;; val powerOfThree : (float -> float) > powerOfThree 2.0;; val it : float = 9.0 >

Log.txt

Test カリー化した関数をTest

まだまだ、タイプミスによるエラーが多い。