CS 61A Discussion 2 Environments and Higher Order Functions Albert - - PowerPoint PPT Presentation

CS 61A Discussion 2

Environments and Higher Order Functions

Slides: albertxu.xyz/teaching/cs61a/

Albert Xu

Announcements

functions can return other functions

functions can return other functions take in functions as arguments

functions can return other functions take in functions as arguments

functions can return other functions take in functions as arguments

>>> f = make_power(3) >>> f(5)

functions can return other functions take in functions as arguments

>>> f = make_power(3) >>> f(5) 125

functions can return other functions take in functions as arguments

functions can return other functions take in functions as arguments

>>> apply_twice(square, 3) 81

Environment Diagrams

let’s look at a function we’ve already seen.

Environment Diagrams

draw an environment diagram. let’s look at a function we’ve already seen.

Environment Diagrams

let’s look at a function we’ve already seen. def statement procedure:

1) Write the function on the right side, with appropriate intrinsic name + parent 2) Write the name of the function on the left in current frame 3) Draw an arrow to the function object on the right! 4) Skip the body.

Environment Diagrams

let’s look at a function we’ve already seen. assignment statement procedure:

1) Evaluate the right hand side 2) Bind that value to a name on the left 3) If the name doesn’t exist in the current frame, add it! Otherwise change the current value

Environment Diagrams

let’s look at a function we’ve already seen. function call procedure:

1) Evaluate the operator 2) Evaluate the operands 3) Open the call frame 4) Bind the parameters 5) Evaluate the body

Environment Diagrams

let’s look at a function we’ve already seen. function call procedure:

1) Evaluate the operator 2) Evaluate the operands 3) Open the call frame 4) Bind the parameters 5) Evaluate the body *don’t open a frame for built-in functions!

Environment Diagrams

let’s look at a function we’ve already seen. function call procedure:

1) Evaluate the operator 2) Evaluate the operands 3) Open the call frame 4) Bind the parameters 5) Evaluate the body

hi

*don’t open a frame for built-in functions!

Environment Diagrams

let’s look at a function we’ve already seen. function call procedure:

1) Evaluate the operator 2) Evaluate the operands 3) Open the call frame 4) Bind the parameters 5) Evaluate the body

hi None

*don’t open a frame for built-in functions!

Environment Diagrams

let’s look at a function we’ve already seen. hi None …and we’re done!

Thanks for coming.

Have a great rest of your week! :)

Attendance: links.cs61a.org/albert-disc Slides: albertxu.xyz/teaching/cs61a/