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Diffstat (limited to 'doc/language/keyword/cpsc-keyword-class.7.md')
| -rw-r--r-- | doc/language/keyword/cpsc-keyword-class.7.md | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/doc/language/keyword/cpsc-keyword-class.7.md b/doc/language/keyword/cpsc-keyword-class.7.md index 2a713c0..6d730aa 100644 --- a/doc/language/keyword/cpsc-keyword-class.7.md +++ b/doc/language/keyword/cpsc-keyword-class.7.md @@ -40,6 +40,8 @@ A constructor is a PROCEDURE named NEW, following guide section 10.2. It may be `DECLARE Object : ClassName` zeroes the object's storage and constructs its fields recursively in declaration order; it then calls NEW only when the class has a parameterless NEW. Otherwise the object stays unconstructed until `Object <- NEW ClassName(arguments)` binds it, as in guide section 10.2. `DECLARE Object : ClassName(arguments)` always calls the matching NEW, so `ClassName()` is an error for a class whose NEW requires arguments, and supplying arguments to a class without NEW is an error. These automatic DECLARE, field and array calls are compiler extensions. Array elements and class-valued fields in records or classes follow the plain DECLARE rule, before the enclosing constructor runs. Constructor arguments after ARRAY OF are unsupported. A declaration executed again, such as inside a loop, first destroys its previous live incarnation, then zeroes and constructs its original storage again. +A single-parameter BYVAL constructor may specify IMPLICIT to allow automatic conversion from its parameter type; see [cpsc-keyword-implicit(7)](cpsc-keyword-implicit.7.md). + An `OVERLOAD PROCEDURE NEW(BYREF Other : ClassName)` defines a copy constructor. BYVAL class lvalue arguments and RETURN of class lvalues invoke it; a same-class BYVAL constructor is rejected. Classes without one retain bitwise copying for fields without STRING ownership. Records and BYVAL arrays recursively clone STRING-bearing fields or elements. Other owning class fields retain the existing shallow-copy limitations. Class results transfer ownership directly into BYVAL arguments, RETURN and ordinary assignment without an assignment overload. Discarded results and temporary receivers live until the statement ends, including exception exits. Ordinary user BYREF calls still require bare variables; constructor calls can bind temporaries. The keyword NEW is allowed only as the complete right side of assignment: `Target <- NEW ClassName`, `Target <- NEW ClassName()` or `Target <- NEW ClassName(arguments)`. Target must have exactly the named class type. NEW requires the memory.cps standard-library unit, imported by default; with **-no-std**, import and supply it explicitly. NEW uses the checked MALLOC allocation path, zeroes storage and constructs fields before calling NEW. A method-only class receives at least one byte of heap storage so its object address is non-null. Allocation failure reports a runtime error and throws; constructor exceptions also propagate to TRY/CATCH. Private constructor access and argument checks follow ordinary member-call rules. |