6.2. Map

This video introduces our first tool for using higher order blocks: Map.


Using Tools

The video shows how to load the new blocks used in this chapter in BYOB. If you are using SNAP (online version), you can just go to the File menu and Import Tools



Snap Tips

SNAP does not have a (copy of (list)) block. That is OK, the only reason I use (copy of (list)) is because otherwise BYOB hides the list from view - SNAP does not have that bug.

See BYOB Chapter 3.1 for how to set up a list in SNAP if you just switched to using it.

Checkpoint Exercises


All of the checkpoint exercises will work on the lists shown to the right. Start by making lists that look like them.

Two other hints:

  1. The map block is your “loop”. You should not be using any repeat blocks!

  2. You should make sure the reporter block you give to map is surrounded by a gray circle. If there is no gray circle, you need to reposition the block.


    The block shown above says “Do [item]+3 with each item in numbers”. Without the gray circle it would say “Do 0 + 3. Take that answer and do it to each item in numbers”… how do we “do 3 to each item”?????


Use Map to make a list where each number in the numbers list is double the value in the original list. (144, 158, 174, 136, 178)


ASCII Converter

Use Map to make a list where the numbers in the numbers list are converted to the letters that they correspond to on the ASCII table.

Hint: use the asciiBlock block (BYOB) or unicodeBlock block (SNAP) to convert a number to a letter. The list should spell a word.


ASCII Encoder

Use Map to make a list where you add 1 to each of the numbers, then turn it from ascii to a letter. It should be an encoded version of the word from #2 where each letter is one place later in the alphabet.


Word Lengther

Use Map to make a list that consists of the length of each word from the list of words. Hint: use the lengthOf block - you should get a list that consists of 1, 4, 11.


First Letter Check

Use Map to make a list that consists of true/false values. Build it by testing each word in the words list to see if the first letter is “p”. You should get the list false, false, true.

Start by using Map to make a list containing the first letter of each word. Then modify that logic to see if the letter is p.