C - 小さなツールの作成 - 1つのことだけをうまくやる(範囲の指定、エラー状態、カンマ区切りデータを読み込み、JSON形式で表示する)

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3章(小さなツールの作成 - 1つのことだけをうまくやる)、ポケットコード(p. 115)を取り組んでみる。

ポケットコード(p. 115)

#include <stdio.h>
#include <stdbool.h>

int main() {
  float latitude;
  float longitude;
  char info[80];
  int started = false;

  puts("data=[");
  while (scanf("%f,%f,%79[^\n]", &latitude, &longitude, info) == 3) {
    if (started) {
      puts(",");
    } else {
      started = true;
    }
    if (latitude < -90 || latitude > 90) {
      printf("緯度(%f)が予想値の範囲外\n", latitude);
      return 2;
    }
    if (longitude < -180 || longitude > 180) {
      printf("経度(%f)が予想値の範囲外\n", longitude);
      return 2;
    }
    printf("{latitude: %f, longitude: %f, info: '%s'}",
           latitude, longitude, info);
  }
  puts("\n]");
}

入出力結果(Terminal)

$ cc sample.c -o sample
$ ./sample < gpsdata1.csv
data=[
{latitude: 42.363400, longitude: -71.098465, info: 'Speed = 21'},
{latitude: 42.363327, longitude: -71.097588, info: 'Speed = 23'},
{latitude: 42.363255, longitude: -71.096710, info: 'Speed = 17'},
{latitude: 42.363182, longitude: -71.095833, info: 'Speed = 22'},
{latitude: 42.363110, longitude: -71.094955, info: 'Speed = 14'},
{latitude: 42.363037, longitude: -71.094078, info: 'Speed = 16'},
{latitude: 42.362965, longitude: -71.093201, info: 'Speed = 18'},
{latitude: 42.362892, longitude: -71.092323, info: 'Speed = 22'},
{latitude: 42.362820, longitude: -71.091446, info: 'Speed = 17'},
{latitude: 42.362747, longitude: -71.090569, info: 'Speed = 23'},
{latitude: 42.362675, longitude: -71.089691, info: 'Speed = 14'},
{latitude: 42.362602, longitude: -71.088814, info: 'Speed = 19'},
{latitude: 42.362530, longitude: -71.087936, info: 'Speed = 16'},
{latitude: 42.362457, longitude: -71.087059, info: 'Speed = 16'},
緯度(423.624573)が予想値の範囲外
$ cat gpsdata1.csv
 42.363400,-71.098465,Speed = 21
 42.363327,-71.097588,Speed = 23
 42.363255,-71.096710,Speed = 17
 42.363182,-71.095833,Speed = 22
 42.363110,-71.094955,Speed = 14
 42.363037,-71.094078,Speed = 16
 42.362965,-71.093201,Speed = 18
 42.362892,-71.092323,Speed = 22
 42.362820,-71.091446,Speed = 17
 42.362747,-71.090569,Speed = 23
 42.362675,-71.089691,Speed = 14
 42.362602,-71.088814,Speed = 19
 42.362530,-71.087936,Speed = 16
 42.362457,-71.087059,Speed = 16
 423.62457,-71.087059,Speed = 16 
 42.362385,-71.086182,Speed = 21$