Consider this an "academic" question. I have been wondering about about avoiding NULLs from time to time and this is an example where I can't come up with a satisfactory solution.

Let's assume I store measurements where on occasions the measurement is known to be impossible (or missing). I would like to store that "empty" value in a variable while avoiding NULL. Other times the value could be unknown. So, having the measurements for a certain time-frame, a query about a measurement withing that time period could return 3 kinds of responses:

• The actual measurement at that time (any numerical value, including 0)
• A "missing"/"empty" value (i.e., a measurement was done, and the value is known to be empty at that point).
• An unknown value (i.e., no measurement has been done at that point. It could be empty, but it could also be any other value).

Important Clarification:

Assuming you had a function get_measurement() returning one of "empty", "unknown" and a real value, then I would like to be able to write code, avoiding NULL checks, for example (pseudocode):

>>> value = get_measurement()  # returns `2`
>>> print(value * 2)
4

>>> value = get_measurement()  # returns `Empty()`
>>> print(value * 2)
Empty()

>>> value = get_measurement()  # returns `Unknown()`
>>> print(value * 2)
Unknown()

Note that none of the print statements caused exceptions (as no NULLs were used). So the empty & unknown values would propagate as necessary and the check whether a value is actually "unknown" or "empty" could be delayed until really necessary (like storing/serialising the value somewhere).

Side-Note: The reason I'd like to avoid NULLs, is primarily a brain-teaser. If I want to get stuff done I'm not opposed to using NULLs, but I found that avoiding them can make code a lot more robust in some cases.

Consider this an "academic" question. I have been wondering about about avoiding NULLs from time to time and this is an example where I can't come up with a satisfactory solution.

Let's assume I store measurements where on occasions the measurement is known to be impossible (or missing). I would like to store that "empty" value in a variable while avoiding NULL. Other times the value could be unknown. So, having the measurements for a certain time-frame, a query about a measurement within that time period could return 3 kinds of responses:

• The actual measurement at that time (for example, any numerical value including 0)
• A "missing"/"empty" value (i.e., a measurement was done, and the value is known to be empty at that point).
• An unknown value (i.e., no measurement has been done at that point. It could be empty, but it could also be any other value).

Important Clarification:

Assuming you had a function get_measurement() returning one of "empty", "unknown" and a value of type "integer". Having a numerical value implies that certain operations can be done on the return value (multiplication, division, ...) but using such operations on NULLs will crash the application if not caught.

I would like to be able to write code, avoiding NULL checks, for example (pseudocode):

>>> value = get_measurement()  # returns `2`
>>> print(value * 2)
4

>>> value = get_measurement()  # returns `Empty()`
>>> print(value * 2)
Empty()

>>> value = get_measurement()  # returns `Unknown()`
>>> print(value * 2)
Unknown()

Note that none of the print statements caused exceptions (as no NULLs were used). So the empty & unknown values would propagate as necessary and the check whether a value is actually "unknown" or "empty" could be delayed until really necessary (like storing/serialising the value somewhere).

Side-Note: The reason I'd like to avoid NULLs, is primarily a brain-teaser. If I want to get stuff done I'm not opposed to using NULLs, but I found that avoiding them can make code a lot more robust in some cases.

Consider this an "academic" question. I have been wondering about about avoiding NULLs from time to time and this is an example where I can't come up with a satisfactory solution.

Let's assume I store measurements where on occasions the measurement is known to be impossible (or missing). I would like to store that "empty" value in a variable while avoiding NULL. Other times the value could be unknown. So, having the measurements for a certain time-frame, a query about a measurement withing that time period could return 3 kinds of responses:

• The actual measurement at that time (any numerical value, including 0)
• A "missing"/"empty" value (i.e., a measurement was done, and the value is known to be empty at that point).
• An unknown value (i.e., no measurement has been done at that point. It could be empty, but it could also be any other value).

Side-Note: The reason I'd like to avoid NULLs, is primarily a brain-teaser. If I want to get stuff done I'm not opposed to using NULLs, but I found that avoiding them can make code a lot more robust in some cases.

Consider this an "academic" question. I have been wondering about about avoiding NULLs from time to time and this is an example where I can't come up with a satisfactory solution.

Let's assume I store measurements where on occasions the measurement is known to be impossible (or missing). I would like to store that "empty" value in a variable while avoiding NULL. Other times the value could be unknown. So, having the measurements for a certain time-frame, a query about a measurement withing that time period could return 3 kinds of responses:

• The actual measurement at that time (any numerical value, including 0)
• A "missing"/"empty" value (i.e., a measurement was done, and the value is known to be empty at that point).
• An unknown value (i.e., no measurement has been done at that point. It could be empty, but it could also be any other value).

Important Clarification:

Assuming you had a function get_measurement() returning one of "empty", "unknown" and a real value, then I would like to be able to write code, avoiding NULL checks, for example (pseudocode):

>>> value = get_measurement()  # returns `2`
>>> print(value * 2)
4

>>> value = get_measurement()  # returns `Empty()`
>>> print(value * 2)
Empty()

>>> value = get_measurement()  # returns `Unknown()`
>>> print(value * 2)
Unknown()

Note that none of the print statements caused exceptions (as no NULLs were used). So the empty & unknown values would propagate as necessary and the check whether a value is actually "unknown" or "empty" could be delayed until really necessary (like storing/serialising the value somewhere).

Side-Note: The reason I'd like to avoid NULLs, is primarily a brain-teaser. If I want to get stuff done I'm not opposed to using NULLs, but I found that avoiding them can make code a lot more robust in some cases.