我学的某门课上提到过：
# Why there are so many programming languages?
Application domains have distinctive/ conflicting needs:
- Scientific Computing(FORTRAN I)

- good float point performance

- good arrays support

- parallelism

- Business Application(SQL)

- Persistence

- report generation

- data analysis

- System programming(C /Cpp)

- control of resources

- real-time constraints

# Why are there new programming languages?
Application domains have distinctive/ conflicting needs:因为需求还没有被满足，所以会有新语言出来。

Programmer training is the dominant cost for a programming language.

1. Widely languages are slow to change

2. Easy to start a new language

If the productivity of a language is greater than its Traning Cost, the developer is willing to change.

And if a new language could fill a void, it would be easier to get adopted.

New languages tend to look like old languages That can reduce the Traning Cost,