Julia基础知识：算数运算，赋值和字符串

• 话题:
  • 算数运算
  • 数字运算
  • 字符串运算

算数运算应该很熟悉

3 + 7 # addition
10 - 3 # subtraction
20 * 5 # multiplication
100 / 10 # division
10 ^ 2 # exponentiation
101 % 2 # remainder (modulus)
sqrt(2) # square root
√2 # Unicode to the rescue: \sqrt + TAB

注意，除以两个整数会产生浮点数。 这里有两个额外的运算符可能会有所帮助：

10 / 6
10 ÷ 6 # \div TAB or the `div` function
div(10, 6)
10 // 6

Numbers:不同方式来书写42

fortytwos = (42, 42.0, 4.20e1, 4.20f1, 84//2, 0x2a)

for x in fortytwos
    show(x)
    println("\tisa $(typeof(x))")
end

位运算

0x2a & 0x70 # AND
0x2a | 0x70 # OR
42 & 112
0b0010 << 2 # == 0b1000

逻辑运算

false&&true #and
false || true # or

注意复合运算

x=-42
x>0||error("x must be positive")

比较运算

1==1.0 # 相等
1===1.0 # 编程相等
3 < π
1<=1
.1+.2
.1+.2≈ .3 # \approx + TAB

比较“链”

尝试在其中一个比较中插入括号
2==2.0==0x02

x=42
0<x<100||error("x must be between 0 and 100")

分配赋值

x=1
y=x
x="hello"
print(y)
ϵ = eps(1.0) # You can make your own unicode names
5ϵ # Juxtaposition is multiplication

复合运算

y+=1==y=y+1
请注意，它只是为新值重新使用相同的名称。 这意味着类型甚至可能会改变：
y/=2

字符串

s1 = "I am a string."
s2 = """I am also a string. """
"Here, we get an "error" because it's ambiguous where this string ends "
"""Look, Mom, no "errors"!!! """
println("""The other nice thing about triple-quoted
            string literals is that they ignore leading
            indentation, which is nice for long strings
            in real code. Try changing these quotes!""")

字符串不是用单个字符编写的,' - 用于单个字符：
first(s1)
'⊂'
'If you try writing a string in single-quotes, you will get an error'

字符串插值

可以在字符串中使用美元符号来评估字符串中的Julia表达式 - 单个变量或更复杂的表达式：

name = "Jane"
num_fingers = 10
num_toes = 10
println("Hello, my name is $name.")
println("I have $num_fingers fingers and $num_toes toes.")

println("That is $(num_fingers + num_toes) digits in all!!")

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