函数-结构体 ppt下载.pptVIP

Expression to Function: y = x * x (lambda (x) (* x x)) float sqr(float x) { return x*x; } y = sqr(x); A small machine that transforms the data it receives into a finished product (x1,x2,…,xn) function ? y Concept of a Function Function Definition general format: return-type functionname ( type parameter1, type parameter2 ) { function body (or block) } top-level only, can’t define from within another function known from position defined in file to end of file components: return type parameters function body Function Definition Function Return a function call expression returns a value Function Parameters Pass values from arguments to parameters Parameters behave like local variables inside the function body; known within the function body specify parameter list as void if the function does not receive any values Function Definition int sum (int a, int b) { return ( a + b ); } Function Prototype Declaration general format: return-type functionname ( type, type ) ; makes function signature known to compiler a function must be defined or its prototype declared before it is used parameter names are optional put at beginning of file after preprocessor directives Function Prototype Declaration Declare Call Call a function general format: functionname ( argument1, argument2 ) arguments: none, one or comma separated list can be a constant, variable or expression must match parameter type in function definition Function Usage Call By Value all parameters in C, even address types, are passed from the calling function to the called function using call by value the called function gets a separate copy of each passed argument the called function cannot change the original value of the argument residing in the calling function for address type parameters, such as array names or pointers, the address itself in the calling function cannot be changed by the called function; however, what is addressed or “point