program10_07.c

C语言入门经典一书的所有代码。书上面的所有代码均在此。希望大家喜欢

/* Program 10.7 Reading and unreading characters */
#include <stdio.h>
#include <ctype.h>
#include <stdbool.h>
#include <string.h>

const size_t LENGTH = 50;

/* Function prototypes */
void eatspaces(void);
bool getinteger(int *n);
char *getname(char *name, size_t length);
bool isnewline(void);

int main(void)
{
  int number;
  char name[LENGTH];
  printf("Enter a sequence of integers and alphabetic names:\n");
  while(!isnewline())
    if(getinteger(&number))
      printf("\nInteger value:%8d", number);
    else if(strlen(getname(name, LENGTH)) > 0)
      printf("\nName: %s", name);
    else
    {
      printf("\nInvalid input.");
      return 1;
    }
  return 0;
}

/* Function to ignore spaces from standard input */
void eatspaces(void)
{
  char ch = 0;
  while(isspace(ch = getchar()));
  ungetc(ch, stdin);
}

/* Function to read an integer from standard input */
bool getinteger(int *n)
{
  eatspaces();
  int value = 0;
  int sign = 1;
  char ch = 0;

  /* Check first character */
  if((ch=getchar()) == '-')            /* should be minus */
    sign = -1;
  else if(isdigit(ch))                 /* ...or a digit   */
   value = 10*value + (ch - '0');
  else  if(ch != '+')                  /* ...or plus      */
  {
    ungetc(ch, stdin);
    return false;                      /* Not an integer  */
  }

  /* Find more digits */
  while(isdigit(ch = getchar()))
    value = 10*value + (ch - '0');

  /* Push back first non-digit character */
  ungetc(ch,stdin);
  *n = value*sign;
  return true;
}

/* Function to read an alphabetic name from input */
char *getname(char *name, size_t length)
{

  eatspaces();                         /* Remove leading spaces */
  size_t count = 0;
  char ch = 0;
  while(isalpha(ch=getchar()))         /* As long as there are letters */
  {
    name[count++] = ch;                /* store them in name           */
    if(count == length-1)
      break;
  }

  name[count] = '\0';                  /* Append string terminator     */
  if(count < length-1)
    ungetc(ch, stdin);                 /* Return non-letter to stream  */
  return name;
}

/* Function to check for newline */
bool isnewline(void)
{
  char ch = 0;
  if((ch = getchar()) == '\n')
    return true;

  ungetc(ch, stdin);
  return false;
}