cs106b课堂笔记1

惭愧了 这么久才又开始学习

abstration

defination

Design that hides the details of how something works while still allowing the user to access complex functionality

what is an abstraction

Key idea:Through a simpler interface, users are able to take full advantage of a complex system without needing to know how it works or how it was made.

includes

angle bracket

use of the angle bracket operators is usually reserved for code from the C++ Standard library

quote

use of the quotes is usually reserved for code from the Stanford C++ libraries, or code in files that you have written yourself

variables and types

variables

A way for code to store information by associating a value with a name
we will think of a variable as a named container storing a value

types

All variables have a type associated with them, where the type describes the representation of the variable.
In C++,all types must be explicitly defined when the variable is created, and a variable cannot change its type.

funtion

anatomy of a function

definition:
parameter(s):
one or more variables that your function expects as input.

argument(s):
the values passed into your function and assigned to its parameter variables.

return value:
the value that your function hands back to the "calling" function.

returnType functionName(varType parameter1, varType parameter2, ...){
    returnType variable = /* Some fancy code */
    /* more code */
    return variable;
}

Pass-by-value is the default mode of operation when it comes to parameters in C++,which means that parameter is passed to function by value,variable is a copy of the variable passed in,changing it inside the function does not change the value in the calling function.

循环什么的不想记（瘫

string

• Strings are mutable in C++
• You can add characters to strings and strings to strings using += and +
  • Strings must use double quotes(““)while characters use single(‘’)
• You can use logical operators to compare strings(and characters)(only comparing the first letter)

when running

string hiThere = "hi"+"there";

you would get a error
cause there are cpp string and c string in cpp,when declare a string like “hi” you would get a c string,which is not allowed to be added together.

when running

string hiThere = "hi"+'!';

you would get a garbage
cause when add a different type to a c string, it would point to random garbage.

C strings vs C++ strings summary

• C strings have no methods
  • This is why you can’t do something like “hi”.length() in C++
• Conversion fixes
  • Store the C string in a variable first to convert it to a C++ string
  • Use a conversion function
    • string(“text”); // converts the C string literal into a C++ string
    • strig.c_str(); // return a C string from a C++ string
      

Takeaway:Beware of C string