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Bug #12090

`Range#cover` does not raise an exception when comparison fails

Added by sawa (Tsuyoshi Sawada) about 3 years ago. Updated about 3 years ago.

Status:
Open
Priority:
Normal
Assignee:
-
Target version:
-
[ruby-core:73894]

Description

The documentation for Range#cover? says,

cover?(obj) → true or false

Returns true if obj is between the begin and end of the range.

This tests begin <= obj <= end when exclude_end? is false and begin <= obj < end when exclude_end? is true.

which implies that, when comparison fails, cover? should raise an error. But actually, it doesn't:

"a" <= 1 # => ArgumentError: comparison of String with 1 failed
1 <= "a" # => ArgumentError: comparison of Fixnum with String failed
("a".."z").cover?(1) # => false

It silently returns false instead of raising an error.

Either Range#cover? should raise an error when comparison fails, or the documentation should be changed to correctly describe this behaviour.

History

Updated by sos4nt (Stefan Schüßler) about 3 years ago

Raising an error would break backward compatibility. Maybe cover? should just return nil to indicate incomparable values.

("a".."z").cover?("c")  # => true
("a".."z").cover?("5")  # => false
("a".."z").cover?(1)    # => nil

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