Itty Bitty Programming Language Assignment
Contents
Credit
This assignment is based on MUPL by Dan Grossman and his team at UW.
Code To Use
Code To Investigate
Ast
Expression Structs
(struct IdentifierExp (name) #:transparent)
(struct IntExp (value) #:transparent)
(struct AddExp (left_exp right_exp) #:transparent)
(struct IfGreaterExp (left_exp right_exp then_body_exp else_body_exp) #:transparent)
(struct NilExp () #:transparent)
(struct IsNilExp (exp) #:transparent)
(struct ConsExp (car_exp cdr_exp) #:transparent)
(struct CarOfConsExp (cons_exp) #:transparent)
(struct CdrOfConsExp (cons_exp) #:transparent)
(struct LetExp (binding_name binding_exp body_exp) #:transparent)
(struct FunctionExp (name_option parameter_name body_exp) #:transparent)
(struct CallExp (function_exp argument_exp) #:transparent)
expression?
(define (expression? exp)
(or (IdentifierExp? exp)
(IntExp? exp)
(AddExp? exp)
(IfGreaterExp? exp)
(NilExp? exp)
(IsNilExp? exp)
(ConsExp? exp)
(CarOfConsExp? exp)
(CdrOfConsExp? exp)
(LetExp? exp)
(FunctionExp? exp)
(CallExp? exp)))
Code To Implement
Warmup
file: | src/main/racket/ibpl/warmup.rkt | ![]() |
functions: | racket-integers->ib-IntExps ib-IntExps->racket-integers |
racket-integers->ib-IntExps
ib-IntExps->racket-integers
Interpreter
file: | src/main/racket/ibpl/interpreter.rkt | ![]() |
functions: | value? expand-environment evaluate |
(struct closure (env function) #:transparent)
value?
IBPL expressions evaluate to Racket values. value?
determines if the paramater v
is a valid value.
Valid value types are cons cells, integers, closures, and the null empty list.
For a cons cell to be a valid value, its car and cdr must be valid values.
ensure-value?
(define (ensure-value? v)
(if (value? v)
v
(raise-argument-error 'v "value?" v)))
lookup-value-in-environment
(struct entry (name value) #:transparent)
(define (lookup-value-in-environment env identifier-name)
(cond [(null? env) (error "unbound identifier during evaluation" identifier-name)]
[(equal? (entry-name (car env)) identifier-name) (entry-value (car env))]
[#t (lookup-value-in-environment (cdr env) identifier-name)]))
expand-environment
(define (expand-environment name value env)
(error 'not-yet-implemented))
Requirement: raise-argument-error for invalid parameters.
evaluate
Evaluate the expression exp
in the environment env
.
The provided shell ensures that the parameters exp
and env
pass expression? and list? respectively. ensure-value? is then used to ensure that what you evaluate the expression to is correctly a value.
(define (evaluate exp env)
(if (expression? exp)
(if (list? env)
(ensure-value?
(error 'not-yet-implemented))
(raise-argument-error 'env "list?" env))
(raise-argument-error 'exp "expression?" exp)))
The evaluation of sub-expressions described below, unless otherwise specified, should be performed in the current environment env
. Any sub-expression evaluation which does not pass what is to be "ensured" should result in an error.
- IdentifierExp evaluates to the value found by looking its name up in the environment.
- NilExp evaluates to the empty list (this is: the value null)
- IntExp evaluates to its value.
- AddExp first evaluates its sub-expressions: left_exp and right_exp, ensures that they are integers, and evaluates to the sum of the left and right values.
- ConsExp first evaluates its sub-expressions: car_exp and cdr_exp, ensures that they are values, and evaluates to a cons cell of the car and cdr values.
- CarOfConsExp first evaluates its sub-expression: cons_exp, ensures that it is a pair, and evaluates to the car of the pair.
- CdrOfConsExp first evaluates its sub-expression: cons_exp, ensures that it is a pair, and evaluates to the cdr of the pair.
- IfGreaterExp
- IsNilExp first evaluates its sub-expression: exp, and evaluates to
1
if it is the empty list, otherwise0
. - LetExp first expands the environment with the binding defined by the binding_name and the evaluation of the sub-expression: binding_exp, then evaluates the sub-expression: body_exp in that expanded environment.
- FunctionExp evaluates to a closure of the environment and the function expression itself.
- CallExp
Macros
file: | src/main/racket/ibpl/warmup.rkt | ![]() |
functions: | IbIfNil IbLet* IbIfEq |
Treat each Racket function as an Itty Bitty macro. Return an abstract syntax tree of expressions which can later be evaluated.
Alert: do not invoke evaluate. Each Racket function's return value should have all of the necessary logic encoded in its AST of expressions.
IbIfNil
IbLet*
(struct binding (name exp) #:transparent)
IbIfEq
Functions
Define Racket values which are abstract syntax trees of expressions that can be later evaluated.
Alert: do not invoke evaluate. Each Racket value you define should have all of the necessary logic encoded in its AST of expressions.
ib-double
; racket version for reference
(define (racket-double n) (+ n n))
ib-sum-curry
; racket version for reference
(define (racket-sum-curry a) (lambda (b) (+ a b)))
ib-call-with-one
; racket version for reference
(define (racket-call-with-one proc) (proc 1))
ib-map
ib-map-add-n
Testing
file: | test_all.rkt | ![]() |
source folder: | src/test/racket/ibpl |
note: ensure that you have removed all printing to receive credit for any assignment.