Integrated exercises I

(総合演習 I)

Computing Practice I

7th lecture, May 24, 2018

http://www.sw.it.aoyama.ac.jp/2018/CP1/lecture7.html

Martin J. Dürst

© 2005-18 Martin J. Dürst 青山学院大学

Today's Schedule

• Written test (30 min)
• About last week's exercises
• The C preprocessor
• About today's exercises

総合復習テスト

• 30 分の筆記試験
• ログオフ済み
• 机に場所を作る (キーボードの長辺を下、倒れないように立たせるなど)
• 授業開始まで教科書、資料、筆箱、財布などを鞄に入れ、鞄を椅子の下に
• テスト終了後その場で待つ

Applications of C: Ruby

• Programming language putting the pleasure of the programmer first
• First publication: 1993
• Creator: Yukihiro Matsumoto (Matz; まつもと ゆきひろ)
• Main application areas: Web programming (Ruby on Rails), scripting
• Overall about 840K lines of code
  (main directory: 92 .c files, 37 .h files)
• Other implementations (Ex.: JRuby: Ruby implemented in Java)

Results of Previous Exercises

• 06C1 not submitted ⇒ No real program submitted
• 06C2 not submitted ⇒ One more chance today

Previous Exercises: How to Define Structures

• Define structures for frequently appearing actual objects
• Fit structure definition to the essence of the objects
• Choose appropriate names for the structure and its members
• The goal of the structure is to group related data items
• Think about structures, functions, and usage separately
• Separate functions for input/output from functions for calculation
• This applies not only to programming, but also to
  requirements analysis and design

Previous Exercises: Examples of Structures

• Bad examples:

  typedef struct  {  double x1, x2, y1, y2;  }  Point;
  typedef struct  {  double x, y; }  Complex;

• Good examples (points in 2D have x and y coordinates; complex numbers have real and immaginary parts)

  typedef struct  {  double x, y;  }  Point;
  typedef struct  {  double real, immaginary;  }  Complex;

• Type names:
  Good examples: Complex, COMPLEX, complex_t, complex_num, ...
  Bad examples: base, CAL, calc, Comps, Decimal, INPUT, Number, POINT, ...

Previous Exercises: How to Obtain Information

• Listen well to explanations at the beginning
• Carefully read the handouts
• Carefully read and understand the exercise description
  Example: Create a function to add two complex numbers.
• How to use the Q&A forum
  • Questions about English text are okay
  • Questions about contents of exercise are okay
  • Questions about C or programming in general are okay
  • Questions about specific checks are okay
  • Questions about individual programming problems are okay
  • Better ask earlier than later
  • There are still reluctant students
  • There are no dumb questions, only not asking a question is dumb

Preprocessor

• Executed before the actual compiler
• Can be called as separate program (cpp)
• Running only the preprocessor: gcc -E 06A1.c -o 06A1.i → 06A1.i
• Main functions:
  • Inclusion of (header) files (#include)
  • Definition and expansion of macros (#define)
  • Conditional compilation (#ifdef/#ifndef/#endif)

Header Files

• The extension for C header files is .h
• Compiled by inclusion into .c files
• Main functions:
  • Share information common to multiple .c files
  • Define common types
  • Declare functions
  • Define macros
  • [declare global variables]

Extensions

• .h: C header file
• .c: C file
• (.i: C file after preprocessor, before compilation)
• .o: C file after compilation (before linking; .obj on Windows)
• .exe: Windows executable file

Typical Example of Header File Use

• library.h: Declaration of types and functions in the library
• library.c: Define the functions in the library (#includes library.h)
• using.c: Program using the library (#includes library.h)

Two Different Kinds of #include

• #include for standard libraries (textbook p. 201):
  #include <stdio.h>
• #include for 'self-made' libraries:
  #include "my_library.h"

Definition of Macros

(textbook pp. 218, 237)

• Basic syntax: #define COUNT 20
  Purpose: Easy change of program
  Example: for (i=0; i<COUNT; i++)
• Extended syntax: #define max(a,b) ((a)>(b)?(a):(b))
  Purpose: Type-independent inline pseudo-functions
  Example: int i = max(d,e); double z = max(x,y);
  Caution: In definition, use lots of parentheses; be careful about side effects
  (char c = max(getchar(), 'n');)
• Definition of macros on command line:
  gcc -DCOUNT=30 ...

Conditional Compilation

• #ifdef HOGE
  // HOGE が #define で定義されたら残る部分
#endif
• #ifndef HOGE
  // HOGE が #define で定義されなかったら残る部分
#endif

Example of Conditional Compilation

Avoid repeated #include of the same header file:

In header file:

#define MY_LIBRARY_HEADER

When including:

#ifndef MY_LIBRARY_HEADER
#include "my_library.h"
#endif

演習問題の概要

• 07A1: 複素数のライブラリの使用
• 07B1: 複素数のライブラリの作成
• 07C1: 行列計算のライブラリの作成と使用 (#ifndef, #define; インデントに注意)
• 07C2: 日付のライブラリの作成 (第一部)
• 07C3: 日付のライブラリの作成 (第二部、発展問題、月曜締切、部分点)

(テスト用のファイル、コンパイル用のファイルがダウンロード可能)

(用意されたファイルと情報源、要求されたファイルの関係を把握)

次回までの準備

• 今日の復習
• 残りの演習問題を宿題として完成、提出
• 配布資料 (「ビジュアルラーニング C++ 入門」、さかお まい著、X-media 社、pp. 70-112) をよく読む。

Glossary

requirements analysis

要求分析

design

設計

header file

ヘッダファイル

preprocessor

プリプロセッサ

linking

リンク (の作業)

expansion

展開

macro

マクロ

conditional compilation

条件付きコンパイル

extension

拡張子