Passing and returning arrays

Build the idea

Start with the concept and its key vocabulary.

Key idea

Pass an array into a sub-program, iterate over its indices and return a processed array or value.

An array can be supplied as a parameter just like one number or string. The sub-program can inspect each element, calculate from it or build a new array to return. Passing the collection keeps the sub-program reusable and avoids a global array. Indices begin at 0, so an ERL loop normally runs from 0 to array.length - 1; Python uses range(len(array)).

Array parameter

A parameter that receives an array or Python list from the caller.

Index

A zero-based position used to access an array element.

Return array

Send a complete processed array back from a function.

Mutable

Able to be changed after creation; Python lists are mutable.

Keep these in mind

Arrays can be passed to procedures and functions.
A function may return an array as its result.
Use the loop counter as the array index.
For a length of 5, valid indices are 0 to 4.
Python lists passed to functions can also be modified in place because they are mutable.

Build the idea

Start with the concept and its key vocabulary.

Key idea

Pass an array into a sub-program, iterate over its indices and return a processed array or value.

Array parameter

A parameter that receives an array or Python list from the caller.

Index

A zero-based position used to access an array element.

Return array

Send a complete processed array back from a function.

Mutable

Able to be changed after creation; Python lists are mutable.

Keep these in mind

Arrays can be passed to procedures and functions.
A function may return an array as its result.
Use the loop counter as the array index.
For a length of 5, valid indices are 0 to 4.
Python lists passed to functions can also be modified in place because they are mutable.