C - 高度な関数 - 関数を最大限に活用する(引数に関数を渡す、関数ポインター)

Head First C
原著

開発環境

• OS: macOS High Sierra - Apple
• Text Editor: Emacs
• コンパイラー: LLVM/Clang, GCC(gcc)
• プログラミング言語: C

Head First C ―頭とからだで覚えるCの基本 (David Griffiths (著)、Dawn Griffiths (著)、中田 秀基 (監修)、木下 哲也 (翻訳)、オライリージャパン)の7章(高度な関数 - 関数を最大限に活用する)、エクササイズ(p. 321)を取り組んでみる。

エクササイズ(p. 321)

Makefile

CC = cc

all: sample run

sample: sample.c
 $(CC) sample.c -o sample

run: sample
 ./sample

コード

#include <stdio.h>
#include <string.h> // strstr

typedef int (*fn_type)(char *s);

int NUM_ADS = 7;
char *ADS[] = {"William: SBM GSOH likes sports, TV, dining",
               "Matt: SWM NS likes art, movies, theater",
               "Luis: SLM ND likes books, theater, art",
               "Mike: DWM DS likes trucks, sports and bieber",
               "Peter: SAM likes chess, working out and art",
               "Josh: SJM likes sports, movies and theater",
               "Jed: DBM likes theater, books and dining"};

int sports_or_workout(char *s) {
  return strstr(s, "sports") || strstr(s, "working");
}
int ns_theater(char *s) { return strstr(s, "NS") && strstr(s, "theater"); }
int arts_theater_or_dining(char *s) {
  return strstr(s, "art") || strstr(s, "theater") || strstr(s, "dining");
}
fn_type matches[] = {sports_or_workout, ns_theater, arts_theater_or_dining,
                     NULL};
char *names[] = {"sports or workout", "ns theater", "arts theater or dining",
                NULL};
void find(fn_type match) {
  puts("検索結果:");
  puts("--------------------------------------------------");
  for (int i = 0; i < NUM_ADS; i++) {
    if (match(ADS[i])) {
      puts(ADS[i]);
    }
  }
  puts("--------------------------------------------------");
}

int main() {
  for (size_t i = 0; matches[i] != NULL; i++) {
    puts(names[i]);
    find(matches[i]);
  }
}

入出力結果(Terminal)

$ make
cc sample.c -o sample
./sample
sports or workout
検索結果:
--------------------------------------------------
William: SBM GSOH likes sports, TV, dining
Mike: DWM DS likes trucks, sports and bieber
Peter: SAM likes chess, working out and art
Josh: SJM likes sports, movies and theater
--------------------------------------------------
ns theater
検索結果:
--------------------------------------------------
Matt: SWM NS likes art, movies, theater
--------------------------------------------------
arts theater or dining
検索結果:
--------------------------------------------------
William: SBM GSOH likes sports, TV, dining
Matt: SWM NS likes art, movies, theater
Luis: SLM ND likes books, theater, art
Peter: SAM likes chess, working out and art
Josh: SJM likes sports, movies and theater
Jed: DBM likes theater, books and dining
--------------------------------------------------
$