不同编程语言中的else if语法关键字
概述
常用的编程语言一般都会提供else if语法，一般这个语法的关键字也就是“else if”串联组合在一起。然而某些语言的else if关键字却很奇怪，比如说Ruby的就是elsif。
以下列出所有之前用过并且记得自己用过的语言中的else if关键字，并且给出一段代码示例。
Golang
else if
这应该是大部分人所预期的语法了。
package main
import (
"fmt"
)
func main() {
x := 100
if x == 50 {
fmt. Println ( "Germany" )
} else if x == 100 {
fmt. Println ( "Japan" )
} else {
fmt. Println ( "Canada" )
}
}
Unix Shell
elif
跟Ruby的相比还是觉得正常一点。
#!/bin/sh
a = 10
b = 20
if [ $a == $b ]
then
echo "a is equal to b"
elif [ $a - gt $b ]
then
echo "a is greater than b"
elif [ $a - lt $b ]
then
echo "a is less than b"
else
echo "None of the condition met"
fi
Java
else if
符合一般习惯。
int time = 22 ;
if ( time < 10 ) {
System . out . println ( "Good morning." );
} else if ( time < 20 ) {
System . out . println ( "Good day." );
} else {
System . out . println ( "Good evening." );
}
// Outputs "Good evening."
C++
else if
符合一般习惯。
int
time =
22
;
if
(time <
10
) {
cout <<
"Good morning."
;
}
else
if
(time <
20
) {
cout <<
"Good day."
;
}
else
{
cout <<
"Good evening."
;
}
// Outputs "Good evening."
Ruby
elsif
就因为这么奇怪，才想到比较一下不同语言的关键字。
#!/usr/bin/ruby
x = 1
if x > 2
puts "x is greater than 2"
elsif x <= 2 and x != 0
puts "x is 1"
else
puts "I can't guess the number"
end
Python
elif
跟Shell的一样。
a =
33
b =
33
if
b > a:
print
(
"b is greater than a"
)
elif
a == b:
print
(
"a and b are equal"
)
JavaScript
else if
符合一般习惯。
<html>
<head>
<script type="text/javascript">
var one = prompt("Enter the first number");
var two = prompt("Enter the second number");
one = parseInt(one);
two = parseInt(two);
if (one == two)
document.write(one + " is equal to " + two + ".");
else if (one<two)
document.write(one + " is less than " + two + ".");
else
document.write(one + " is greater than " + two + ".");
</script>
</head>
<body>
</body>
</html>
C#
else if
符合一般习惯。
using System;
namespace Conditional
{
class IfElseIfStatement
{
public static void Main ( string [] args)
{
int number = 12 ;
if (number < 5 )
{
Console.WriteLine( "{0} is less than 5" , number);
}
else if (number > 5 )
{
Console.WriteLine( "{0} is greater than 5" , number);
}
else
{
Console.WriteLine( "{0} is equal to 5" );
}
}
}
}
Lua
elseif
将else if粘在一起写，也还算直观的。
--[[
In Lua, if, elseif and else use then and end
clauses to delimit the conditional code
]]
j = 45
-- == for equality testing
if j==45 then print ("yes") end
if j==47 then print ("no") end
-- ~= for NOT equals
if j~=47 then print ("two nose make a yes") end
-- chaining with elseif and endif
if j<40 then print ("small") elseif j>50 then print ("big") else print ("between") end
-- much better to write it as blocks down the screen!
range = 7
if j<40 then
print ("tiny")
range = range + 2
elseif j>50 then
print ("huge")
range = range + 6
else
print ("middlin")
range = range + 4
end
print ("range is " .. range)
--[[ ----------------------------- Sample Output -------------
[trainee@easterton u103]$ lua lif
yes
two nose make a yes
between
middlin
range is 11
[trainee@easterton u103]$
]]
Rust
else if
符合一般习惯。
fn main() {
// All have type `Option<i32>`
let number = Some(7);
let letter: Option<i32> = None;
let emoticon: Option<i32> = None;
// The `if let` construct reads: "if `let` destructures `number` into
// `Some(i)`, evaluate the block (`{}`).
if let Some(i) = number {
println!("Matched {:?}!", i);
}
// If you need to specify a failure, use an else:
if let Some(i) = letter {
println!("Matched {:?}!", i);
} else {
// Destructure failed. Change to the failure case.
println!("Didn't match a number. Let's go with a letter!");
}
// Provide an altered failing condition.
let i_like_letters = false;
if let Some(i) = emoticon {
println!("Matched {:?}!", i);
// Destructure failed. Evaluate an `else if` condition to see if the
// alternate failure branch should be taken:
} else if i_like_letters {
println!("Didn't match a number. Let's go with a letter!");
} else {
// The condition evaluated false. This branch is the default:
println!("I don't like letters. Let's go with an emoticon :)!");
}
}
R
else if
符合一般习惯。
# Create vector quantiy
quantity <- 10
# Create multiple condition statement
if (quantity <20) {
print('Not enough for today')
} else if (quantity > 20 &quantity <= 30) {
print('Average day')
} else {
print('What a great day!')
}
Perl
elsif
跟Ruby的一样。
print "Enter salary\n" ;
$a = <>;
chomp ( $a );
print "Enter sex M/F\n" ;
$b = <>;
chomp ( $b );
if ( $a > 10000 && $b eq "M" ){
print "Your salary is good and you are a male\n" ;
}
elsif ( $a > 10000 && $b eq "F" ){
print "Your salary is good and you are a female\n" ;
}
elsif ( $a <= 10000 && $b eq "M" ){
print "Your salary is not so good and you are a male\n" ;
}
elsif ( $a <= 10000 && $b eq "F" ){
print "Your salary is not so good and you are a female\n" ;
}
else {
print "Enter valid input\n" ;
}
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