Intro to C++ for Robotics Made for ALARM

Computer System Hardware – cpu, memory, i/o Software – OS, drivers

Steps in writing software From ideas to stuff a computer will run

C++ - a quick intro Look at some code

IDE (Integrated Development Environment) Editing Saving Compiling Linking Debugging

Breakpoints, watching variables, stepping

C++ - program structure.h - Header files – contain definitions – aka signatures.cc – contain the “code” or how to do what it does

Compiler Directives #include – brings in definition files #define – sets up literal names for unchanging values

C++ Basic Program structure Main Where everything starts, creates and calls other software until task is done. Statement Ends in ; White space does not matter to the compiler, but matter a LOT to the engineer. Compound statements are contained in { } Attributes (aka variables) Methods (aka functions)

C++ Arithmetic Operators Operator NameSyntax UnaryUnary Plus +a+a Addition (Sum) a + b Prefix IncrementIncrement ++a Postfix IncrementIncrement a++ Assignment by Addition a += b Unary Minus (Negation) -a-a Subtraction (Difference) a - b Prefix DecrementDecrement --a Postfix DecrementDecrement a-- Assignment by Subtraction a -= b Multiplication (Product) a * b Assignment by Multiplication a *= b Division (Quotient) a / b Assignment by Division a /= b ModulusModulus (Remainder) a % b Assignment by Modulus a %= b

C++ Comparison Operators Operator NameSyntax Less Than a < b Less Than or Equal To a <= b Greater Than a > b Greater Than or Equal To a >= b Not Equal To a != b Equal To a == b Logical Negation !a!a Logical AND a && b Logical OR a || b Any operation can given a True or False value 0 is False Anything else is True 2 + 3; is True 0 / 1234; is False Comparison operators return an integer (0 for False, 1 for True) int i = !( 2 >= 5);

C++ Bitwise Operators Operator NameSyntax Bitwise Left Shift a << b Assignment by Bitwise Left Shift a <<= b Bitwise Right Shift a >> b Assignment by Bitwise Right Shift a >>= b Bitwise One's Complement ~a~a Bitwise AND a & b Assignment by Bitwise AND a &= b Bitwise OR a | b Assignment by Bitwise OR a |= b Bitwise XOR a ^ b Assignment by Bitwise XOR a ^= b

C++ Other Operators Basic Assignment a = b FunctionFunction, Call a() ArrayArray Subscript a[b]a[b] IndirectionIndirection (Dereference) *a*a Address-ofAddress-of (Reference) &a&a Member by PointerPointer a->b Member a.ba.b Member by Pointer Function Pointer Indirection a->*b Member Function Pointer Indirection a.*b Cast (type) atype Comma a, b Ternary Conditional a ? b : c Scope Resolution a::b Member Function Pointer a::*b Size-of sizeof a sizeof(t ype)t ype Type Identification typeid(a) typeid(t ype)t ype Allocate Storage new typetype Allocate Storage (Array) new type[n]type Deallocate Storage delete a Deallocate Storage (Array) delete[] a

C++ Operators – try out some math Math - addition (+), subtraction (-), multiplication (*), division (/), and modulus (%). Code up this fragment in a new project and find the answers. int n1 = 7; int n2 = 2; int ans1 = 0, ans2 = 0, ans3 = 0, ans4 = 0, ans5 = 0; ans1 = n1 + n2; ans2 = n1 - n2; ans3 = n1 * n2; ans4 = n1 / n2; ans5 = n1 % n2;

C++ Program structure – For loop for (int i = 0; i < MAX_NUMBER_OF_CATS + 1; i++) { listOfCats[i] = NULL; }

C++ Program structure – While loop while (cat_p != NULL) { delete cat_p; cat_p = listOfCats[++postionInList]; }

C++ Program structure – Do loop So what does this code fragment do? char ch = ‘a’; do { cout << ch << ‘ ‘; ch++; } while ( ch <= ‘z’ ); Now see what other characters are out there, change the initial value of ch to 0 (not ‘0’) and the final value to 254 (not ‘254’). (Why did I pick that range?, try going over 254 and see what happens.)

C++ Program structure – If/else if (sensor_inputs.raw_direction_cmd < 123) { if (Front_cal_needed) { pwm06 = CALIBRATE_RIGHT_SPEED; CALIBRATE_FRONT_LED = LED_ON; /* signal calibrating the front */ } else { pwm05 = CALIBRATE_RIGHT_SPEED; CALIBRATE_BACK_LED = LED_ON; /* signal calibrating the back */ } } else if (sensor_inputs.raw_direction_cmd > 133) { if (Front_cal_needed) { pwm06 = CALIBRATE_LEFT_SPEED; CALIBRATE_FRONT_LED = LED_ON; /* signal calibrating the front */ } else { /* assume it is back */ pwm05 = CALIBRATE_LEFT_SPEED; CALIBRATE_BACK_LED = LED_ON; /* signal calibrating the back */ }

C++ Program structure – switch char* Pet::GetGenderAsString() { char* genderString; switch (itsGender) { case Male: genderString = "Male"; break; case Female: genderString = "Female"; break; default: genderString = "???"; break; } // end gender switch return genderString; }

C++ Attributes (aka variables): Definition All the variables that a program is going to use must be declared prior to use associates a type and a name with the variable allows the compiler to decide how much storage space to allocate for storage of the value associated with the identifier and to assign an address

C++ Attributes: Scope Attribute is only defined within the “block” of code that it was declared in. Can re-use names in different blocks (advanced topic – namespaces) Typically attributes are defined To be globally available in an include file used by everyone (see static modifier) As part of a class or structure At the start of a method At the start of a code control block (e.g. for loop) Scope operator is :: Cat::getAge(); Declaration is different than using “new”

C++ Attributes: Pointers/References Every variable has an address. Even without knowing the specific address of a given variable, you can store that address in a pointer Use naming convention foo_p So what does this do? int myAge = 47; int* foo_p = 0; foo_p = &myAge; myAge++; cout << *foo_p; Now try and increment the age using foo_p instead of myAge++.

C++ - Attributes: Built in types int represent negative and positive integer values Typically stored in one word (16 bits), with a range of to char a letter, a digit or a punctuation character Typically stored as a byte in memory (8 bits) with a range of 0 – 255. (Recall the do loop example.) bool hold the values true (1) or false (0) Typically stored as a byte (8 bits) in memory float any real numeric value Memory and accuracy depends on the system

C++ Attributes: Modifiers Const – value can not be changed Static – only one instance created in memory Extern – defined in some other file Long – modifies integer to be two words Unsigned – modifies integer to be only positive Double – modifies float to have twice the range

C++ Attributes: User defined types - typedef You can create types Typedef char* String_p; -- somewhere later --- String_p myName_p = 0;

C++ Attributes: User defined types - Arrays collection of data storage locations, each of which holds the same type of data Keyword are the square brackets, [] int ages[6] int IntegerArray[] = { 10, 20, 30, 40, 50 }; int theArray[5][3] Cat* listOfCats[10] (this is a BAD name – why?) How many fence posts you need for a 10-foot fence if you need one post for every foot?

C++ Attributes: User defined types - Structures structure is just a collection of variables typedef struct { int age; char name[80]; bool cool; } personAttributes;

C++ Attributes: User defined types - Classes class is a special structure - just a collection of variables - PLUS a set of related functions class Cat : public Pet { unsigned int itsAge; unsigned int itsWeight; Meow(); };

C++ Attributes: User defined types – Classes data hiding Private – only this class can get at it Protected – only this class and inheriting classes can get at it Public – everyone has access class Cat : public Pet { Private: unsigned int itsAge; unsigned int itsWeight; Protected: int getWeight(); Public: Meow(); int getAge(); };

C++ Attributes: User defined types – Classes - Inheritance Define classes that derive from one another such that one is a specialization of the other. A cat is a pet is a mammal is a animal The derived class can modify the attributes and methods of the base class The base class can leave things undefined using the virtual key word, meaning that the derived class MUST define it. Now add a fish to the collection of pets