|
Class: MeasurementValue
Object
|
+--Magnitude
|
+--ArithmeticValue
|
+--Number
|
+--MeasurementValue
- Package:
- stx:libbasic
- Category:
- Magnitude-Numbers
- Version:
- rev:
1.15
date: 2017/07/01 17:33:33
- user: cg
- file: MeasurementValue.st directory: libbasic
- module: stx stc-classLibrary: libbasic
- Author:
- Claus Gittinger
A MeasurementValue is a numeric value with an error, such as returned
by measurement devices (Volt-Meter). For example, if a measurement-device has
an error of 10%, a measured value of 20 could be any value between 18 and 22.
Arithmetic operations keep track of the error; if any operand is a MeasurementValue,
the operation returns a MeasurementValue as result.
This class is possibly unfinished and needs more arithmetic methods.
For now, the stuff found here represents our needs and more might be added in the future.
Also notice, that instances do not keep the error as a fraction, but instead a min. and maxValue.
That means, that we can handle the case where the error is different in
the positive and negative directions.
I am not sure if this is more flexibility than needed in the long run.
Number
Float
ShortFloat
Fraction
FixedPoint
Integer
Complex
FloatArray
DoubleArray
constants
-
unity
-
return the neutral element for multiplication
usage example(s):
-
zero
-
return the neutral element for addition (0 +/- 0)
usage example(s):
instance creation
-
value: valueArg error: errorArg
-
return a new measurementValue with a given value and an error (fraction)
usage example(s):
10 with an error of 20%:
MeasurementValue value:10 error:0.2
|
-
value: valueArg minValue: minArg maxValue: maxArg
-
return a new measurementValue with a given value and an error given as min-max values.
Use this, if the error is not the same in both directions
usage example(s):
an order of magnitude error:
MeasurementValue value:5 minValue:1 maxValue:10
10 percent:
MeasurementValue value:10 minValue:9 maxValue:11
|
accessing
-
maxValue
-
the maximum possible value, considerung what has been measured and what the measurement error is
-
minValue
-
the minimum possible value, considerung what has been measured and what the measurement error is
-
value
-
the measured value
arithmetic
-
* aNumber
-
return the product of the receiver and the argument.
Care for the error to propagate into the result.
usage example(s):
(MeasurementValue value:-10 error:0.2) * (MeasurementValue value:-10 error:0.2)
(MeasurementValue value:-10 error:0.2) * 2
|
-
+ aNumber
-
return the sum of the receiver and the argument.
Care for the error to propagate into the result.
usage example(s):
(MeasurementValue value:-10 error:0.2) + (MeasurementValue value:-10 error:0.2)
(MeasurementValue value:-10 error:0.2) + 2
|
-
- aNumber
-
return the difference of the receiver and the argument.
Care for the error to propagate into the result.
usage example(s):
(MeasurementValue value:-10 error:0.2) - (MeasurementValue value:-10 error:0.2)
(MeasurementValue value:-10 error:0.2) - 10
(MeasurementValue value:10 error:0.2) - 10
|
-
/ aNumber
-
return the quotient of the receiver and the argument.
Care for the error to propagate into the result.
coercing & converting
-
+/- error
-
return a MeasurementValue with a given error.
-
coerce: aNumber
-
convert the argument aNumber into an instance of the receiver's class and return it.
-
generality
-
return the generality value - see ArithmeticValue>>retry:coercing:
usage example(s):
adding 1 to the value's generality has the subtle side effect of enforcing
|
comparing
-
< aNumber
-
return true, if the argument is greater than the receiver.
Care for the error - i.e. compare against my maximum-value
-
= aNumber
-
hard to tell, what we want here...
How about: aNumber between:minValue and:maxValue ???
-
hash
-
-
lessFromFloat: aFloat
-
aFloat < self ?
-
lessFromInteger: anInteger
-
anInteger < self ?
printing & storing
-
printOn: aStream
-
(5 +/- 1) storeString
(MeasurementValue value:5 minValue:3 maxValue:8) storeString
private accessing
-
value: valueArg error: errorFraction
-
-
value: valueArg minValue: minValueArg maxValue: maxValueArg
-
queries
-
error
-
the relative error.
If the error is different in the min/max direction, the larger error is returned here
usage example(s):
(MeasurementValue value:10 error:0.2) errorLow
(MeasurementValue value:10 error:0.2) errorHigh
(MeasurementValue value:10 error:0.2) error
|
-
errorHigh
-
the relative error on the max side
usage example(s):
(MeasurementValue value:10 error:0.2) errorLow
(MeasurementValue value:10 error:0.2) errorHigh
(MeasurementValue value:10 error:0.2) error
(MeasurementValue value:20 error:0.2) errorLow
(MeasurementValue value:20 minValue:1 maxValue:100) errorLow
(MeasurementValue value:20 minValue:1 maxValue:100) errorHigh
(MeasurementValue value:20 minValue:1 maxValue:100) error
|
-
errorLow
-
the relative error on the min side
usage example(s):
(MeasurementValue value:10 error:0.2) errorLow
(MeasurementValue value:10 error:0.2) errorHigh
(MeasurementValue value:10 error:0.2) error
(MeasurementValue value:20 error:0.2) errorLow
(MeasurementValue value:20 minValue:1 maxValue:100) errorLow
(MeasurementValue value:20 minValue:1 maxValue:100) errorHigh
(MeasurementValue value:20 minValue:1 maxValue:100) error
|
testing
-
between: min and: max
-
Instance creation message in number:
arithmetic; notice, how the errors accumulate:
(100 +/- 5) * 2
(100 +/- 5) * (100 +/- 10)
(100 +/- 5) + (100 +/- 10)
(100 +/- 5) - (100 +/- 10)
|
again see, how the errors accumulate...
|voltage current power|
voltage := MeasurementValue value:10 error:0.05.
current := MeasurementValue value:2 error:0.1.
power := voltage * current.
power.
power minValue.
power maxValue.
|
|voltage current power|
voltage := MeasurementValue value:10 error:0.05.
current := 2.
power := voltage * current.
power
|
|voltage doubleVoltage|
voltage := MeasurementValue value:10 error:0.1.
doubleVoltage := 2 * voltage.
doubleVoltage
|
|