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| author | Hans Bolinder <[email protected]> | 2016-10-07 08:19:46 +0200 |
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| committer | Hans Bolinder <[email protected]> | 2016-10-07 08:19:46 +0200 |
| commit | 1c18d72600eb2156c6dee75026d8cb904249fbaa (patch) | |
| tree | a4ea1cee8c73d94f3f06bf9ce86e485ea858467d /system | |
| parent | 5acfcf3758f89ba32d44807cd8cb406a55d39836 (diff) | |
| parent | 0411bfded2ee9aefb8178a47d139b54913490d5b (diff) | |
| download | otp-1c18d72600eb2156c6dee75026d8cb904249fbaa.tar.gz otp-1c18d72600eb2156c6dee75026d8cb904249fbaa.tar.bz2 otp-1c18d72600eb2156c6dee75026d8cb904249fbaa.zip | |
Merge branch 'rohrer/doc/undefined_fields/PR-1189' into maint
* rohrer/doc/undefined_fields/PR-1189:
Update per review comments.
Fix reference to automatic `undefined` field declared types.
Diffstat (limited to 'system')
| -rw-r--r-- | system/doc/reference_manual/typespec.xml | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/system/doc/reference_manual/typespec.xml b/system/doc/reference_manual/typespec.xml index 1899efd5f3..ced584ed35 100644 --- a/system/doc/reference_manual/typespec.xml +++ b/system/doc/reference_manual/typespec.xml @@ -409,11 +409,13 @@ The initial values for fields are to be compatible with (that is, a member of) the corresponding types. This is checked by the compiler and results in a compilation error - if a violation is detected. For fields without initial values, - the singleton type <c>'undefined'</c> is added to all declared types. - In other words, the following two record declarations have identical - effects: + if a violation is detected. </p> + <note> + <p>Before Erlang/OTP 19, for fields without initial values, + the singleton type <c>'undefined'</c> was added to all declared types. + In other words, the following two record declarations had identical + effects:</p> <pre> -record(rec, {f1 = 42 :: integer(), f2 :: float(), @@ -423,9 +425,10 @@ f2 :: 'undefined' | float(), f3 :: 'undefined' | 'a' | 'b'}).</pre> <p> - For this reason, it is recommended that records contain initializers, - whenever possible. + This is no longer the case. If you require <c>'undefined'</c> in your record field + type, you must explicitly add it to the typespec, as in the 2nd example. </p> + </note> <p> Any record, containing type information or not, once defined, can be used as a type using the following syntax: |