structure and union types 程式設計 潘仁義 ccu comm. structure type definition struct...

Structure and Union TypesStructure and Union Types

程式設計潘仁義

CCU COMM

Structure Type DefinitionStructure Type Definitionstruct

structured data objects, can be defined by users

#define STRSIZ 10

typedef struct {char name[STRSIZ];double diameter; /* diameter in km */int moons; /* number of moons */

double orbit_time, /* years to orbit sun once */rotation_time; /* hours to rotate once */

} planet_t;

int main (){ planet_t current_planet, blank_planet = {“”, 0,0,0,0};

int status = scan_planet(&current_planet); /* 等會看 */

current_planet = get_planet();print_planet(current_planet);…

Assigning Values to Components Assigning Values to Components of Variable current_planetof Variable current_planet

Function with a Structured Input ParameterFunction with a Structured Input Parameter

Function Comparing Two Structured Values Function Comparing Two Structured Values for Equalityfor Equality

Function with a Structured Output ArgumentFunction with a Structured Output Argument

也可寫成& plnp->diameter,&plnp->moons,& plnp->orbit_time,&plnp->rotation_time);

Data Areas of main and scan_planet during Data Areas of main and scan_planet during Execution of status = scan_planet (&currentExecution of status = scan_planet (&current_planet);_planet);

Function get_planet Returning a Structured Function get_planet Returning a Structured Result TypeResult Type

Data Type planet_t and Basic OperationsData Type planet_t and Basic Operations

例如 : 課本的 complexFigure 11.10

Parallel Arrays and an Array of StructuresParallel Arrays and an Array of Structures

int id[50];double gpa[50];

struct {int id;double gpa;

} stulist[50];

Union typesUnion types

UnionTo deal with situations in which one needs a data object that can be interpreted in a variety of ways.

typedef union {int wears_wig; /* 載假髮嗎 ?*/char color[20];

} hair_t;

typedef struct {int bald; /* 禿頭嗎 ?*/hair_t h;

} hair_info_t;

Function That Displays a Structure with a Function That Displays a Structure with a Union Type ComponentUnion Type Component

Q & AQ & A

union 可以用 -> 嗎 ?

struct planet_t a, b;a = b; /* 可這麼寫嗎 ? */if(a == b) {} /* 可這麼寫嗎 ? */

(*plnp).name*plnp.nameplnp->name&plnp->name

小心： union 的內容該如何解釋 ?