标签：cas lines fork var operator one like top cut
Conditionals
Conditional expressions allow your programs to make decisions and take different forks in the road,depending on the value of variables or user input.
C provides a few different ways to implement conditional expressions (also know as branches ) in your programs,some of which likely look familiar from Scratch.
if (and if-else,and if-else..else)
Use Boolean expressions to make descisions.
if (boolean-expression)
{
statements;
}
if the boolean-expression evaluates to true,all lines of code between the curly braces will execute in order from top-to-bottom.
if the boolean-expression evaluates to false,those lines of code will not execute.
if (boolean-expression)
{
statements;
}
else
{
statements;
}
if the boolean-expression evaluates to true,all lines of code between the first set of curly braces will execute in order from top-to-bottom.
if the boolean-expression evaluates to false,all lines of code between the second set of curly braces will execute in order from top-to-bottom.
switch statement
Use discrete cases to make decisions
int x = GetInt();
switch(x)
{
case 1;
printf("One!\n");
break;
case 2:
printf("Two!\n");
break;
case 3:
printf("Three!\n");
break;
default:
printf("Sorry!\n");
}
C‘s switch() statement is a conditional statement that permits enumeration of discrete cases,instead of relying on Boolean expressions.
It‘s important to break;between each case,or you will "fall throug" each case (unless that is desired behavior).
The ternary operator (?:)
Use to replace a very simple if-else to make your code look fancy
cool but not a good idea
int x;
if (expr)
{
x = 5;
}
else
{
x = 5;
}
Next
int x = (expr) ? 5 : 6;
These two snippets of code act identically. // 这两段代码片段作用相同
The ternary operator (?:) is mostly a cute trick,but is useful for writing tricially short conditional branches.Be familiar with it,but know that you won‘t need to write it if you don‘t want to. // 三元操作符(?:)是一个不错的技巧
标签：cas lines fork var operator one like top cut
原文地址：https://www.cnblogs.com/jllin/p/9926599.html
