glossary.dd

Ddoc

$(D_S Glossary,

$(DL

	$(DT $(LNAME2 blit, $(ACRONYM BLIT, Block Transfer)))
	$(DD Also known as BLT, blit refers to copying memory
	byte for byte. In C, this is referred to as a memcpy
	operation.
	The name originated with the BLT instruction on the
	DEC PDP-10 computer.
	)

	$(DT $(LNAME2 ctfe, $(ACRONYM CTFE, Compile Time Function Evaluation)))
	$(DD Refers to the ability to execute regular D
	functions at compile time rather than at run time.)

	$(DT code point) $(DD In Unicode terminology, a $(LUCKY code point)
	is a logical character. The range of code points is $(D 0)
	through $(D 0x10FFFF). Only $(D dchar)s can store code points
	directly; arrays of $(D char) and $(D wchar) need to use the
	variable-length encodings $(LUCKY UTF-8) and $(LUCKY UTF-16).)

	$(DT $(LNAME2 cow, $(ACRONYM COW, Copy On Write)))
	$(DD COW is a memory management strategy where (usually large) reference
	objects are copied if they are to be modified. The constant overhead of COW can be
	high, but may be preferable in applications that would otherwise do a lot of
	preemptive copying.
	)

	$(DT $(LEGACY_LNAME2 data_race, data-race, Data Race)) $(DD Two or more threads writing to
	the same memory location. Program behavior may depend on the arbitrary
	sequencing of these memory accesses.
	)

	$(DT $(LNAME2 functor, Functor)) $(DD A user-defined type (struct or
	class) that defines the function call operator ($(D opCall) in D) so it
	can be used similarly to a function.
	)

	$(DT $(LNAME2 gc, $(ACRONYM GC, Garbage Collection)))
	$(DD Garbage collection is the common name for the
	term automatic memory management. Memory can be allocated and used,
	and the GC will automatically free any chunks of memory no longer
	referred to. In contrast, explicit memory management
	is where the programmer must carefully match up each allocation with
	one and only one call to free().
	)

	$(DT Higher-order function) $(DD A function that either accepts another
	function as a parameter, returns a function, or both.
	)

    $(DT $(LNAME2 ifti, $(ACRONYM IFTI, Implicit Function Template Instantiation)))
	$(DD Refers to the ability to instantiate a template function
    without having to explicitly pass in the types to the template.
    Instead, the types are infered automatically from the types of the
    runtime arguments.)

	$(DT Illegal)
	$(DD A code construct is illegal if it does not conform to the
	D language specification.
	This may be true even if the compiler or runtime fails to detect
	the error.
	)

	$(DT Input range) $(DD A type (i.e., a struct or a class) that
	defines the member functions empty, head, and next. Input ranges
	are assumed to be strictly one-pass: there is no way to save the
	state of the iteration in a copy of the range. See also $(LINK2
	phobos/std_range.html,range).)

	$(DT Implementation Defined Behavior)
	$(DD This is variation in behavior of the D language in a manner
	that is up to the implementor of the language.
	An example of implementation defined behavior would be the size in
	bytes of a pointer: on a 32 bit machine it would be 4 bytes, on
	a 64 bit machine it would be 8 bytes.
	Minimizing implementation defined behavior in the language will
	maximize the portability of code.
	)

	$(DT $(LNAME2 lvalue, lvalue))
	$(DD An lvalue is an abstract term referring to a value with an accessible
	address (through e.g. the unary $(D &) operator). Typical examples of
	lvalues include variables, constants introduced with `const` or `immutable`
	(but not `enum`), and elements of arrays and associative arrays. Calls to
	functions that return `ref` and pointer dereference expressions are also
	lvalues. Lvalues can be passed to (or be returned from) functions by
	reference. An lvalue is the counterpart to an rvalue.
	)

	$(DT $(LNAME2 nrvo, $(ACRONYM NRVO, Named Return Value Optimization)))
	$(DD
	$(P NRVO is a technique invented by Walter Bright around
	1991 (the term for it was coined later) to minimize copying of struct
	data.
	Functions normally return their function return values in
	registers. For structs, however, they often are too big to
	fit in registers. The usual solution to this is to pass to
	the function a $(I hidden pointer) to a struct instance in the
	caller's stack frame, and the return value is copied there.
	For example:
	)
---
struct S { int a, b, c, d; }

S foo()
{
    S result;
    result.a = 3;
    return result;
}

void test()
{
    S s = foo();
}
---

	$(P is rewritten as:)

---
S* foo(S* hidden)
{
    S result;
    result.a = 3;
    *hidden = result;
    return hidden;
}

void test()
{
    S tmp;
    S s = *foo(&tmp);
}
---
	$(P This rewrite gives us an extra temporary object $(D tmp),
	and copies the struct contents twice.
	What NRVO does is recognize that the sole purpose of $(D result)
	is to provide a return value, and so all references to $(D result)
	can be replaced with $(D *hidden).
	$(D foo) is then rewritten as:
	)
---
S* foo(S* hidden)
{
    hidden.a = 3;
    return hidden;
}
---
	$(P A further optimization is done on the call to $(D foo) to eliminate
	the other copy, giving:)
---
void test()
{
    S s;
    foo(&s);
}
---
	$(P The result is written directly into the destination $(D s),
	instead of passing through two other instances.)
	)

	$(DT $(LEGACY_LNAME2 narrow strings, narrow-strings, narrow strings)) $(DD All arrays
	that use $(D char), $(D wchar), and their qualified versions are
	narrow strings. (Those include $(D string) and $(D
	wstring)). Range-oriented functions in the standard library handle
	narrow strings specially by automatically decoding the UTF-encoded
	characters.)

	$(DT $(LEGACY_LNAME2 opApply, op-apply, opApply))
	$(DD A special member function used to iterate over a
	collection; this is used by the
	$(LINK2 spec/statement.html#opApply, $(I ForeachStatement)).
	)

	$(DT $(LEGACY_LNAME2 opApplyReverse, op-apply-reverse, opApplyReverse))
	$(DD A special member function used to iterate over a
	collection in the reverse order; this is used by the
	$(LINK2 spec/statement.html#opApplyReverse, $(I ForeachStatement)).
	)

	$(DT $(LNAME2 pod, $(ACRONYM POD, Plain Old Data)))
	$(DD Refers to a struct that contains no hidden members,
	does not have virtual functions, does not inherit,
	has no destructor,
	and can be initialized and copied via simple bit copies.
	)

	$(DT $(LNAME2 predicate, Predicate)) $(DD A function or
	delegate returning a Boolean result. Predicates can be nullary
	(take no arguments), unary (take one argument), binary (take
	two arguments), or n-ary (take n arguments). Usually
	predicates are mentioned within the context of higher-order
	functions, which accept predicates as parameters.
	)

	$(DT $(LNAME2 raii, $(ACRONYM RAII, Resource Acquisition Is Initialization)))
	$(DD RAII refers to the technique of having the destructor
	of a class object called when the object goes out of scope.
	The destructor then releases any resources acquired by
	that object.
	RAII is commonly used for resources that are in short supply
	or that must have a predictable point when they are released.
	RAII objects in D are created using the $(D scope) storage class.
	)

	$(DT $(LNAME2 rvalue, rvalue))
	$(DD An rvalue is an abstract term referring to a value resulting from an
	expression that has no accessible memory address. This lack of address is
	only conceptual; the implementation has the liberty to store an rvalue in
	addressable memory. Rvalues cannot be changed and cannot be passed to (or
	be returned from) functions by reference. An rvalue is the counterpart to
	an lvalue.
	)

	$(DT $(LEGACY_LNAME2 sequential_consistency, sequential-consistency, Sequential Consistency))
	$(DD Data being written in one order in one thread
	being visible in the same order to another thread.
	)

	$(DT $(LNAME2 sfinae, $(ACRONYM SFINAE, Substitution Failure Is Not An Error)))
	$(DD If template argument deduction results in a type
	that is not valid, that specialization of the template
	is not considered further. It is not a compile error.
	See also $(LINK2 https://en.wikipedia.org/wiki/Substitution_failure_is_not_an_error, SFINAE).
	)

	$(DT $(LNAME2 tmp, $(ACRONYM TMP, Template Metaprogramming)))
	$(DD TMP is using the template features of the language to
	execute programs at compile time rather than runtime.)

	$(DT $(LNAME2 tls, $(ACRONYM TLS, Thread Local Storage)))
	$(DD TLS allocates each thread its own instance of the
	global data. See also
	$(LINK2 https://en.wikipedia.org/wiki/Thread-local_storage, Wikipedia).)

	$(DT $(LEGACY_LNAME2 undefined_behavior, undefined-behavior, $(ACRONYM UB, Undefined Behavior)))
	$(DD Undefined behavior happens when an illegal code construct is
	executed. Undefined behavior can include random, erratic results,
	crashes, faulting, etc.
	A buffer overflow is an example of undefined behavior.
	)

	$(DT $(LNAME2 uda, $(ACRONYM UDA, User-Defined Attribute)))
	$(DD $(LINK2 spec/attribute.html#uda, $(I User-defined attributes)) are
	metadata attached to symbols used for compile-time reflection.)

	$(DT $(LNAME2 ufcs, $(ACRONYM UFCS, Uniform Function Call Syntax)))
	$(DD $(LINK2 spec/function.html#pseudo-member, Uniform function call
	syntax) refers to the ability to call a function as if it were a method of
	its first argument. For example `funct(arg)` may be written as
	`arg.funct()`.)
)

)

Macros:
	TITLE=Glossary
    D=<span class="d_inlinecode">$0</span>