factor-day-1.factor

!! EASY

! Using only * and +, how would you calculate 3^2 + 4^2 with Factor?
3 3 * 4 4 * +
clear

! Enter USE: math.functions in the Listener. Now, with sq and sqrt,
! calculate the square root of 3^2 + 4^2.
USE: math.functions
3 sq 4 sq + sqrt
clear

! If you had the numbers 1 2 on the stack, what code could you use to end up
! with 1 1 2 on the stack?
1 2 over swap
clear

! Enter USE: ascii in the Listener. Put your name on the stack, and write a
! line of code that puts "Hello," in front of your name and converts the whole
! string to uppercase. Use the append word to concatenate two strings and
! >upper to convert to uppercase. Did you have to do any stack shuffling to
! get the desired result?
"Josh"
"Hello, " swap append >upper
clear


!! MEDIUM

! The reduce word taks a sequence, an intial value, and a quotation and
! returns the result of applying the quotation to the initial value and the
! first element of the sequence, then the result of applying th quotation to
! the result and th next element of the sequence, and so on. Using reduce,
! write a line of code that returns the sum of the numbers 1, 4, 17, 9, 11.
! Try it out on your own first, but if you are truly stuck, look back
! carefully over the pages you've just read. There is a hint hiding somewhere.
{ 1 4 17 9 11 } 0 [ + ] reduce ! -> 42
clear

! Now calculate the sum of the numbers 1 to 100 in a similar fashion. Do not
! manually write the sequence of numbers. Instead, enter USE: math.ranges in
! the Listener, and use the [1,b] word to produce the sequence.
USE: math.ranges
100 [1,b] 0 [ + ] reduce ! -> 5050
clear

! The map word takes a sequence and a quotation, and returns a sequence of
! results of applying the quotation to each value. Using map and the words
! that you have learned so far, write a line of code that returns the squares
! of the numbers 1 to 10.
10 [1,b] [ sq ] map ! -> { 1 4 9 16 25 36 49 64 81 100 }
clear


!! HARD

! Write a line of code that, given a number between 1 and 99, returns the
! two digits in the number. That is, given 42 <your code>, you should get 4
! and 2 on the stack. Use the words /i, mod, and bi to accomplish the task.
42 [ 10 /i ] [ 10 mod ] bi

! Repeat the previous exercise for any number of digits. Use a different
! strategy, though: first convert the number to a string, then iterate over
! each character, converting each character back to a string and then to a
! number. Enter USE: math.parser in the Listener and use number>string,
! string>number, 1string, and each.
USE: math.parser
42 number>string [ 1string ] each [ string>number ] bi@
clear