プログラミング学習の記録 351.2「『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), 2(パターンマッチ)

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。3.2(パターンマッチ)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 isOdd x = (x % 2 = 1) let describeNumber x = match isOdd x with | true -> printfn "xは奇数" | true -> printfn "xは偶数";; match isOdd x with ----------^^^^^^^ stdin(4,11): warning FS0025: Incomplete pattern matches on this expression. For example, the value 'false' may indicate a case not covered by the pattern(s). | true -> printfn "xは偶数";; ------^^^^ stdin(6,7): warning FS0026: This rule will never be matched val isOdd : int -> bool val describeNumber : int -> unit > let isOdd x = (x % 2 = 1) let describeNumber x = match isOdd x with | true -> printfn "xは偶数";; match isOdd x with ----------^^^^^^^ stdin(9,11): warning FS0025: Incomplete pattern matches on this expression. For example, the value 'false' may indicate a case not covered by the pattern(s). val isOdd : int -> bool val describeNumber : int -> unit > let isOdd x = (x % 2 = 1) let describeNumber x = match isOdd x with | true -> printfn "xは奇数" | false -> printfn "xは偶数";; val isOdd : int -> bool val describeNumber : int -> unit > describeNumber 1;; xは奇数 val it : unit = () > describeNumber 2;; xは偶数 val it : unit = () > describeNumber 3;; xは奇数 val it : unit = () > List.map describeNumber [1 .. 10];; xは奇数 xは偶数 xは奇数 xは偶数 xは奇数 xは偶数 xは奇数 xは偶数 xは奇数 xは偶数 val it : unit list = [null; null; null; null; null; null; null; null; null; null] > List.iter describeNumber [1 .. 10];; xは奇数 xは偶数 xは奇数 xは偶数 xは奇数 xは偶数 xは奇数 xは偶数 xは奇数 xは偶数 val it : unit = () > let testAnd x y = match x, ywith | true, true -> true | true, true -> true ----^ stdin(23,5): error FS0010: Unexpected symbol '|' in expression. Expected 'with' or other token. ;; > let testAnd x y = mathc x, y with | true, true -> true mathc x, y with ---------------^^^^ stdin(26,16): error FS0010: Unexpected keyword 'with' in interaction. Expected incomplete structured construct at or before this point, ';', ';;' or other token. let testAnd x y= match x, y with |true,true -> true |true,false -> false |false,true -> false |flase,false -> flase let testOr x y= match x, y with |true,true -> true |true,false -> true |false, true -> true |false,false -> false;; > ;; > let testAnd x y= match x, y with |true,true -> true |true,false -> false |false,true -> false |flase,false -> flase;; val testAnd : bool -> bool -> bool > let testOr x y= match x, y with |true,true -> true |true,false -> true |false, true -> true |false,false -> false;; val testOr : bool -> bool -> bool > testAnd true true;; val it : bool = true > testOr true true;; val it : bool = true > testAnd true false;; val it : bool = false > testOr true false;; val it : bool = true > testAnd false true;; val it : bool = false > testOr false true;; val it : bool = true > testAnd false false;; val it : bool = false > testOr false false;; val it : bool = false > let testAnd x y= match x, y with |true, true -> true |_,_ ->false;; val testAnd : bool -> bool -> bool > testAnd true false;; val it : bool = false > test false false;; test false false;; ^^^^ stdin(66,1): error FS0039: The value or constructor 'test' is not defined > testAnd false false;; val it : bool = false > let testOr x y= match x, y with |false,false -> false |_,_ -> true;; val testOr : bool -> bool -> bool > testOr false false;; val it : bool = false > testOr true false;; val it : bool = true > testOr false true;; val it : bool = true > testOr true true;; val it : bool = true >

少しでもコードを記述して毎日継続することを大切にする。