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Constrained genericity: Difference between revisions
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// an instance of a Banana FoodBox
let someBananas = FoodBox [Banana(); Banana()]</lang>
=={{header|Forth}}==
{{works with|Forth}}
Works with any ANS Forth with one dependency
Needs the FMS-SI (single inheritance) library code located here:
http://soton.mpeforth.com/flag/fms/index.html
<lang forth>include FMS-SI.f
include FMS-SILib.f
\ This code uses an implementation dependent word dfa>xt
\ which converts a data-field address to an executable token.
: dfa>xt ( a-addr -- xt ) \ implementation dependent for VFX Forth
5 - ;
: where { class-xt where-xt -- flag }
begin
class-xt ['] object <>
while
class-xt where-xt = if true exit then
class-xt >body sfa @ dfa>xt to class-xt
repeat false ;
:class Eatable
:m eat ;m
;class
\ FoodBox is defined without using eat in any way.
:class FoodBox
object-list eatable-types
:m fill: { n class-xt -- }
class-xt ['] Eatable where
if n 0 do class-xt eatable-types xtadd: loop
else ." not an eatable type "
then ;m
:m test:
begin eatable-types each:
while eat cr ." successful eat"
repeat ;m
;class
FoodBox fb
3 ' Eatable fb fill:
fb test:
successful eat
successful eat
successful eat
FoodBox fb1
5 ' object fb1 fill: \ => not an eatable type
:class apple <super Eatable
;class
:class green-apple <super apple
;class
5 ' green-apple fb1 fill:
fb1 test:
successful eat
successful eat
successful eat
successful eat
successful eat
</lang>
=={{header|Go}}==
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