12 주 강의

The preprocessor

The use of #include

• #include <stdio.h>• #include “filename” ::: current directory syst

em-dependent places

• #include <filename> ::: system dependent places unix :: /usr/include

#define

• #define identifier token_string • #define PI 3.14159• #define SECONDS_PER_DAYS (60*60*24)

• Syntactic sugar– #define EQ ==– #define do /* blank */– while (I EQ 1) do { ….

Macros with arguments

• #define identifier(identifier, …, identifier) token_stringopt

• #define SQ(x) ((x)*(x))– SQ(7+w) ((7+w)*(7+w))– SQ(SQ(*p)) ((((*p) * (*p))) * (((*p) * (*

p))))• #define SQ(x) x*x

– SQ(a+b) a + b * a + b

Micros(Cont.)

• #define SQ(x) (x) * (x)– 4/SQ(2) 4/(2)*(2)

• #define SQ (x) ((x) * (x))– SQ(7) (x) ((x) * (x)) (7)

• #define SQ(x) ((x) * (x); /* error */– x=SQ(y); x = ((y)*(y));;– if (x ==2) x=SQ(y); else ++x;

syntax error

Micros(cont.)

• #define min(x,y) (((x) < (y)) ? (x) : (y))• m=min(u,v) ;• #define SQ(x) ((x) * (x))• #define CUBE(x) (SQ(x) * (x))• #define F_POW(x) sqrt(sqrt(CUBE(x)))• #undef identifier

– Undef F_POW

Type definitions and stddef.h

• typedef char uppercase;• stddef.h

– typedef int ptrdiff_t;– typedef short wchar_t;– typedef unsigned size_t;

• #define NULL ((void *) 0)

Sorting with qsort()

• stdlib.h– void qsort(void *array, size_t n_els, size_t

el_size, int compare(const void *, const void *));

– int compare(const void *, const void *)

Macros with arguments

• 377 page 설명

The Macros in stdio.h and ctype.h

• <stdio.h>– #define getchar() getc(stdin)– #define putchar(c) put((c), stdout)

<ctype.h>Macro Nonzero (true) is returned if:

isalpha(c ) c is a letter

isupper(c ) c is an uppercase letter

islower (c ) c is a lowercase letter

isdigit (c ) c is a digit

isalnum (c ) c is a letter or digit

isxdigit (c ) c is a hexadecimal digit

isspace (c ) c is a white space character

ispunct (c ) c is a punctuation character

isprint (c ) c is printable character

isgraph (c ) c is printable, but not a space

iscntrl (c ) c is a control character

isascii(c ) c is an ASCII code

<ctype.h> (cont.)Call to the function

or macroValue returned

toupper(c ) corresponding uppercase value or c

tolower(c ) corresponding lowercase value or c

toascii(c ) corresponding ASCII value

Conditional compilation

• #if constant_integral_expression• #ifdef identifier• #ifndef identifier• #endif• #undef identifier• defined identifier – defined(identifier)

예• #if defined(HP9000) || defined(SUN4) && !defined(VAX) ….

/*machine-dependent code */ #endif• #define DEBUG 1• #if DEBUG printf(“debug: a = %d\n”, a); #endif

예 2

• #define DEBUG• #ifdef DEBUG ….. #endif• #include “everything.h” #undef PIE #define PIE “I like apple.”

#elif, #else

• #elif• #endif• #if #elif #elif #else #endif

Predefined macros

Predefined Value

_DATE_ A string containing the current date

_FILE_ A string containing the file name

_LINE_An integer representing the current line number

_STDC_If the implementation follows ANSI Standard C,then the value the is a nonzero integer

_TIME_ A string containing the current time

# (ANSI C)

• # stringization – #define message_for(a,b) \ printf(#a “ and ” #b “: We love you!\n”) int main(void) { message_for(Carole, Debra); return 0; }

## (ANSI C)

• Merge tokens• #define X(i) x##i X(1) = X(2) = X(3); x1 = x2 = x3

assert()

• assert(p != NULL); assert(n>0 && n<7);• 389 page 설명

#error, #pragma

• #if A_SIZE < B_SIZE #error “Incompatible sizes” #endif

• #pragma tokens

Line Numbers, etc.

• #line integral_constant “filename”

• #undefine isalpha /* access the function, not the macro */

Quicksort

• 간단히 설명• 모르면 넘어간다

숙제• 학교 1, 6, 8• 집 5, 7, 13, 16, 20, 21• 30 을 해결하면 추가 점수 부여