Re: math.sum returns as a valid an object thatt should be a RangeError

[pmags]

Thanks -- I wasn't aware of `.push checks: off` or even that run-time type 
checking could be completely disabled!

This seems like it would be important to document in the intro section of the 
`math` module docs. I'll file an issue on GitHub.

Re: math.sum returns as a valid an object thatt should be a RangeError

[SolitudeSF]

whats strange is that if you just copy the function from math to current module 
it will raise properly. 


type Probability = range[0.0..1.0]

proc sum*[T](x: openArray[T]): T {.noSideEffect.} =
  ## Computes the sum of the elements in ``x``.
  ##
  ## If ``x`` is empty, 0 is returned.
  ##
  ## See also:
  ## * `prod proc <#prod,openArray[T]>`_
  ## * `cumsum proc <#cumsum,openArray[T]>`_
  ## * `cumsummed proc <#cumsummed,openArray[T]>`_
  runnableExamples:
doAssert sum([1, 2, 3, 4]) == 10
doAssert sum([-1.5, 2.7, -0.1]) == 1.1
  for i in items(x): result = result + i

let ps = @[Probability 0.5, 0.5, 0.5]

# The following line raises properly
echo "Using math sum: ", sum(ps), " typeof: ", typeof(sum(ps))


Run

Re: math.sum returns as a valid an object thatt should be a RangeError

[SolitudeSF]

ah, its not strange at all, math module just explicitly disables all checks 


{.push checks: off, line_dir: off, stack_trace: off.}


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math.sum returns as a valid an object thatt should be a RangeError

[pmags]

Consider the following toy code for representing Probability types. Applying 
the `math.sum` function to an array/seq of Probabilities that sum to more than 
1.0 should return a RangeError, but it doesn't. However, exactly the same 
implementation as math.sum (see 
[https://github.com/nim-lang/Nim/blob/version-1-0/lib/pure/math.nim#L204)](https://github.com/nim-lang/Nim/blob/version-1-0/lib/pure/math.nim#L204\)),
 but no longer generic on T, does return a RangeError as expected.

> How is it that the generic function manages to create an invalid Probability 
> variable in the code below? Is this a compiler bug?


import math
type Probability = range[0.0..1.0]

proc probSum(ps: openArray[Probability]): Probability =
  for p in items(ps):
result += p

let ps = @[Probability 0.5, 0.5, 0.5]

# The following line should raise an error, but doesn't
echo "Using math sum: ", sum(ps), " typeof: ", typeof(sum(ps))

# This line raises and error
# echo "Using probSum: ", probSum(ps), " typeof: ", typeof(probSum(ps))



Run