102 lines
2.3 KiB
C
102 lines
2.3 KiB
C
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#include <stdio.h>
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#include <ctype.h>
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#include <assert.h>
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#include <math.h>
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int getint(int *p);
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int getfloat(float *p);
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/* ungetchar: push char c back to input stream */
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#define ungetchar(c) ungetc(c, stdin)
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/* tests getfloat, prints input to output, puts valid numbers
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* in brackets : n -> [n] */
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int main()
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{
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float x;
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int r;
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while ((r = getfloat(&x)) != EOF)
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if (!r) {
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int c;
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putchar(getchar());
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while (!isdigit(c = getchar()) && c != EOF && c != '-' && c != '+')
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putchar(c);
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ungetchar(c);
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} else
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printf("[%g]", x);
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return 0;
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}
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/* we assert that EOF is negative */
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static_assert(EOF < 0, "EOF is not a negative number");
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/* ugetint: gets unsigned int from input to n
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* n must be intialized by caller
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* takes optional arguments for loop increment
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* last char read is stored in varvar_c */
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#define ugetint(var_c, n, ...) \
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do { \
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for (; isdigit(var_c = getchar()); __VA_ARGS__) \
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n = 10 * (n) + var_c - '0'; \
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} while (0)
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/* getint : gets int from input and overwrites it to p
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* returns 1 on valid integer, 0 if no integer is found
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* and EOF on EOF. */
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int getint(int *p)
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{
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int c;
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if ((c = getchar()) == EOF)
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return EOF;
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/* handle sign */
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int sign = (c == '-') ? -1 : ((c == '+') ? 1 : 0);
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if (sign)
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c = getchar();
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if (!isdigit(c)) { /* not a number */
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ungetchar(c);
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if (sign)
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ungetchar((sign > 0) ? '+' : '-');
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return 0;
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}
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*p = c - '0';
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ugetint(c, *p);
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ungetchar(c);
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*p *= (sign) ? sign : 1;
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return 1;
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}
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#define DEC_SEP X('.') X(',')
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#define EXP_SEP X('e') X('E')
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/* getfloat : gets float from input and overwrites it to p
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* returns 1 on valid integer, 0 if no integer is found
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* and EOF on EOF. */
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int getfloat(float *p)
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{
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char flag;
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int n;
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if ((flag = getint(&n)) < 1) /* not a number */
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return flag;
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*p = n;
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int exp, c = getchar();
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/* fractional part */
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#define X(C) c == C ||
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if (DEC_SEP 0) {
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n = exp = 0;
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ugetint(c, n, exp--);
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*p += n * pow(10, exp);
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}
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#undef X
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/* exponent part */
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#define X(C) c == C ||
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if ((EXP_SEP 0) && getint(&exp)) {
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*p *= pow(10, exp);
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} else
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ungetchar(c);
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return 1;
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}
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