▼Programming Languages:   Application and Interpretation
►3 GC Mutator Scheme
On this page:
3.1 Building Mutators
allocator-setup
3.2 Mutator API
if
and
or
cond
case
define-values
let
let-values
let*
set!
quote
begin
define
lambda
λ
error
add1
sub1
zero?
+
-
*
/
even?
odd?
=
<
>
<=
>=
symbol?
symbol=?
number?
boolean?
empty?
eq?
cons
cons?
first
rest
set-first!
set-rest!
empty
print-only-errors
halt-on-errors
import-primitives
3.3 Testing Mutators
test/  location=?
test/  value=?
printf
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3 GC Mutator Scheme

 #lang plai/mutator package: plai-lib

The GC Mutator Scheme language is used to test garbage collectors written with the GC Collector Scheme language. Since collectors support a subset of Scheme’s values, the GC Mutator Scheme language supports a subset of procedures and syntax. In addition, many procedures that can be written in the mutator are omitted as they make good test cases. Therefore, the mutator language provides only primitive procedures, such as +, cons, etc.

3.1 Building Mutators

The first expression of a mutator must be:

syntax

(allocator-setup collector-module
                 heap-size)
 
heap-size = exact-nonnegative-integer
The collector-module form specifies the path to the garbage collector that the mutator should use. The collector must be written in the GC Collector Scheme language.

The rest of a mutator module is a sequence of definitions, expressions and test cases. The GC Mutator Scheme language transforms these definitions and statements to use the collector specified in allocator-setup. In particular, many of the primitive forms, such as cons map directly to procedures such as gc:cons, written in the collector.

3.2 Mutator API

The GC Mutator Scheme language supports the following procedures and syntactic forms:

syntax

if

Just like Racket’s if.

syntax

and

Just like Racket’s and.

syntax

or

Just like Racket’s or.

syntax

cond

Just like Racket’s cond.

syntax

case

Just like Racket’s case.

syntax

define-values

Just like Racket’s define-values.

syntax

let

Just like Racket’s let.

syntax

let-values

Just like Racket’s let-values.

syntax

let*

Just like Racket’s let*.

syntax

set!

Just like Racket’s set!.

syntax

quote

Just like Racket’s quote.

syntax

begin

Just like Racket’s begin.

syntax

(define (id arg-id ...) body-expression ...+)

Just like Racket’s define, except restricted to the simpler form above.

syntax

(lambda (arg-id ...) body-expression ...+)

syntax

(λ (arg-id ...) body-expression ...+)

Just like Racket’s lambda and λ, except restricted to the simpler form above.

value

error : procedure?

Just like Racket’s error.

value

add1 : procedure?

Just like Racket’s add1.

value

sub1 : procedure?

Just like Racket’s sub1.

value

zero? : procedure?

Just like Racket’s zero?.

value

+ : procedure?

Just like Racket’s +.

value

- : procedure?

Just like Racket’s -.

value

* : procedure?

Just like Racket’s *.

value

/ : procedure?

Just like Racket’s /.

value

even? : procedure?

Just like Racket’s even?.

value

odd? : procedure?

Just like Racket’s odd?.

value

= : procedure?

Just like Racket’s =.

value

< : procedure?

Just like Racket’s <.

value

> : procedure?

Just like Racket’s >.

value

<= : procedure?

Just like Racket’s <=.

value

>= : procedure?

Just like Racket’s >=.

value

symbol? : procedure?

Just like Racket’s symbol?.

value

symbol=? : procedure?

Just like Racket’s symbol=?.

value

number? : procedure?

Just like Racket’s number?.

value

boolean? : procedure?

Just like Racket’s boolean?.

value

empty? : procedure?

Just like Racket’s empty?.

value

eq? : procedure?

Just like Racket’s eq?.

procedure

(cons hd tl) → cons?

  hd : any/c
  tl : any/c
Constructs a (mutable) pair.

procedure

(cons? v) → boolean?

  v : any/c
Returns #t when given a value created by cons, #f otherwise.

procedure

(first c) → any/c

  c : cons?
Extracts the first component of c.

procedure

(rest c) → any/c

  c : cons?
Extracts the rest component of c.

procedure

(set-first! c v) → void?

  c : cons?
  v : any/c
Sets the first of the cons cell c.

procedure

(set-rest! c v) → void?

  c : cons?
  v : any/c
Sets the rest of the cons cell c.

syntax

empty

The identifier empty is defined to invoke (gc:alloc-flat '()) wherever it is used.

value

print-only-errors : procedure?

Behaves like PLAI’s print-only-errors.

value

halt-on-errors : procedure?

Behaves like PLAI’s halt-on-errors.

Other common procedures are left undefined as they can be defined in terms of the primitives and may be used to test collectors.

Additional procedures from scheme may be imported with:

syntax

(import-primitives id ...)

Imports the procedures id ... from scheme. Each procedure is transformed to correctly interface with the mutator. That is, its arguments are dereferenced from the mutator’s heap and the result is allocated on the mutator’s heap. The arguments and result must be heap-value?s, even if the imported procedure accepts or produces structured data.

For example, the GC Mutator Scheme language does not define modulo:

(import-primitives modulo)
 
(test/value=? (modulo 5 3) 2)

3.3 Testing Mutators

GC Mutator Scheme provides two forms for testing mutators:

syntax

(test/location=? mutator-expr1 mutator-expr2)

test/location=? succeeds if mutator-expr1 and mutator-expr2 reference the same location on the heap.

syntax

(test/value=? mutator-expr scheme-datum/quoted)

test/value=? succeeds if mutator-expr and scheme-datum/expr are structurally equal. scheme-datum/quoted is not allocated on the mutator’s heap. Futhermore, it must either be a quoted value or a literal value.

syntax

(printf format mutator-expr ...)

 
format = literal-string
In GC Mutator Scheme, printf is a syntactic form and not a procedure. The format string, format is not allocated on the mutator’s heap.

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