Use SCHEME lang

htdp$.$org

racket$-$lang.org

drRacket IDE

Use Teaching language

Advanced student

Must show attempt to execute

Write documentation for the following code then code:

$4-$Function Calculator$($mycalc no op no$)$

Do in a single line of code

Re$-$implement reverse function for arbitrary list

no "for" or "loop" function

use recursion instead

use "cons" and "append" function

Count no of $"$e$"$ in a arbitrary list

list example

$($list head, tail$1,$ tail$2,$ tail $3,$dots $)=$ populated list

$($list$)=$ empty list

Notes for the HW:

Lambda's job is to construct functions.

Method of terminating recursion:

Are we there yet?

Least amount of work?

Who can I get to do the rest of the work?

Figure out where to locate head of list and its proceeding tails

Restricted form of Scheme only has $1$ operation $($name parms$)$

$($name of the function, parameter of function$)$

Define lambda: Use explicit use of lambda

scheme has functions:

$+\frac{-{?}^{**}}{?}$

$($list$)$ car cdr cons append if

car gets the head

cdr gets the tail

cons adds an element to front of list

append appends the list

Scheme lang example used in class:

Sum Function:

Terminates when there are no more numbers to add

$($define mysum

$($lambda$($x$)($

$($if$($equal$?$x$($list$))0$

$(+($carx$)($mysum$($cdrx$)))))$

square function example in scheme

$(($lambda$(\{$:$(x){(}^{**}))5)$

$=25$

pass $5$ into the lambda $(x)$ function which performs ${(}^{**})$ which are a prefix function