Nim/changelog.md

v0.18.0 - dd/mm/yyyy

Changes affecting backwards compatibility

• Removed basic2d/basic3d out of the stdlib and into Nimble packages. These packages deprecated however, use the glm, arraymancer, neo or another package.
• Arrays of char cannot be converted to cstring anymore, pointers to arrays of char can! This means $ for arrays can finally exist in system.nim and do the right thing.
• echo now works with strings that contain \0 (the binary zero is not shown) and nil strings are equal to empty strings.
• JSON: Deprecated getBVal, getFNum, and getNum in favour to getBool, getFloat, getBiggestInt. Also getInt procedure was added.
• reExtended is no longer default for the re constructor in the re module.
• The overloading rules changed slightly so that constrained generics are preferred over unconstrained generics. (Bug #6526)
• It is now possible to forward declare object types so that mutually recursive types can be created across module boundaries. See package level objects for more information.
• The unary < is now deprecated, for .. < use ..< for other usages use the pred proc.
• We changed how array accesses "from backwards" like a[^1] or a[0..^1] are implemented. These are now implemented purely in system.nim without compiler support. There is a new "heterogenous" slice type system.HSlice that takes 2 generic parameters which can be BackwardsIndex indices. BackwardsIndex is produced by system.^. This means if you overload [] or []= you need to ensure they also work with system.BackwardsIndex (if applicable for the accessors).
• mod and bitwise and do not produce range subtypes anymore. This turned out to be more harmful than helpful and the language is simpler without this special typing rule.
• Added algorithm.rotateLeft.
• rationals.toRational now uses an algorithm based on continued fractions. This means its results are more precise and it can't run into an infinite loop anymore.
• Added typetraits.$ as an alias for typetraits.name.
• os.getEnv now takes an optional default parameter that tells getEnv what to return if the environment variable does not exist.
• Removed PDCurses wrapper from the stdlib and published it as a separate Nimble package.
• The parsing rules of if expressions were changed so that multiple statements are allowed in the branches. We found few code examples that now fail because of this change, but here is one:

.. code-block:: nim

t[ti] = if exp_negative: '-' else: '+'; inc(ti)

This now needs to be written as:

.. code-block:: nim

t[ti] = (if exp_negative: '-' else: '+'); inc(ti)