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Accumulator factory: Difference between revisions
Replace existing solution by a more general one and add a solution using a customized number type.
(Replace existing solution by a more general one and add a solution using a customized number type.) |
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=={{header|Nim}}==
Nim being a static typed language, if the accumulator function was created with an integer, it will always return an integer. So, it isn’t possible to mix integers and float.
Three solutions are possible:
:– convert
:– give the accumulator type the type of the initial value provided at the creation;
:– use a customized type.
We provide the code for the two last solutions.
<lang Nim>
proc accumulator[T: SomeNumber](x: T): auto =
var sum = x
result = proc (n: T): T =
sum += n
result = sum
echo
echo
let y = accumulator(3.5)
echo y(2) # 5.5
echo y(3) # 8.5
</lang>
{{out}}
<pre>
6
8
5.5
8.5
</pre>
==={Customized number typed}===
<lang Nim>
type
# Kind of numbers. We limit this example to "int" and "float".
NumberKind = enum kInt, kFloat
# Customized number type (using variants).
Number = object
case kind: NumberKind
of kInt: ival: int
of kFloat: fval: float
# The converters allow transparent conversion from int or float to Number.
converter toNumber(n: int): Number = Number(kind: kInt, ival: n)
converter toNumber(n: float): Number = Number(kind: kFloat, fval: n)
#---------------------------------------------------------------------------------------------------
proc accumulator[T: int|float](x: T): auto =
## Factory procedure.
# Allocate the accumulator storage.
when T is int:
var sum = Number(kind: kInt, ival: x)
elif T is float:
var sum = Number(kind: kFloat, fval: x)
# Create the accumulator procedure.
result = proc (n: Number): Number =
case sum.kind
of kInt:
case n.kind
of kInt:
# Add an int to an int.
sum.ival += n.ival
of kFloat:
# Add a float to an int => change the kind of accumulator to float.
sum = Number(kind: kFloat, fval: sum.ival.toFloat + n.fval)
of kFloat:
case n.kind
of kInt:
# Add an int to a float.
sum.fval += n.ival.toFloat
of kFloat:
# Add a float to a float.
sum.fval += n.fval
result = sum
#---------------------------------------------------------------------------------------------------
proc `$`(n: Number): string =
## Display the accumulator contents as an int or a float depending of its kind.
case n.kind
of kInt: $n.ival
of kFloat: $n.fval
#---------------------------------------------------------------------------------------------------
let acc = accumulator(1)
echo acc(5) # 6
discard accumulator(3) # Create another accumulator.
echo acc(2.3) # 8.3
</lang>
{{out}}
<pre>
6
8.300000000000001
</pre>
=={{header|Nit}}==
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