静态/动态类型语言 & 强/弱类型语言

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静态/动态类型语言

Static/Dynamic typing is about when type information is aquired (Either at compiletime or at runtime)

静态类型语言比较不容易出差错，很多问题能提前检查出来。而动态语言比较灵活，用起来比较浪

In a statically typed language the type is static, meaning once you set a variable to a type, you CANNOT change it. That is because typing is associated with the value rather than the variable. (静态类型语言中类型与变量是一个整体)

For example in Java:

String str = "Hello";  //statically typed as string
str = 5;               //would throw an error since java is statically typed

Whereas in a dynamically typed language the type is dynamic, meaning after you set a variable to a type, you CAN change it. That is because typing is associated with the value rather than the variable. (动态类型语言中类型与值是一个整体)

For example in Python:

str = "Hello" # it is a string
str = 5       # now it is an integer; perfectly OK

强/弱类型语言

Strong/Weak typing is about how strictly types are distinguished (e.g. whether the language tries to do implicit conversion from strings to numbers).

For example in Python:

str = 5 + "hello"
# would throw an error since it does not want to cast one type to the other implicitly.

whereas in PHP:

$str = 5 + "hello"; // equals 5 because "hello" is implicitly casted to 0
// PHP is weakly typed, thus is a very forgiving language.