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Merged
dlang-bot merged 3 commits into from
Apr 27, 2018
Merged

Improve *Foreach over Tuples* spec #2248

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b375bb8
Change CT tuple -> sequence [statement.dd]
ntrel Feb 23, 2018
202f0ce
Improve wording of *Foreach over Sequences* & example
ntrel Feb 23, 2018
d47264d
Fix foreach index types
ntrel Apr 11, 2018
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64 changes: 33 additions & 31 deletions spec/statement.dd
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Original file line number Diff line number Diff line change
Expand Up @@ -458,7 +458,7 @@ $(GNAME ForeachAggregate):
$(P
$(I ForeachAggregate) is evaluated. It must evaluate to an expression
of type static array, dynamic array, associative array,
struct, class, delegate, or tuple.
struct, class, delegate, or sequence.
The $(PS0) is executed, once for each element of the
aggregate.
At the start of each iteration, the variables declared by
Expand All @@ -485,8 +485,8 @@ $(P
If there are
two variables declared, the first is said to be the $(I index)
and the second is said to be the $(I value). The $(I index)
must be of $(D int), $(D uint) or $(D size_t) type,
it cannot be $(I ref),
must be of `int`, `uint`, `long` or `ulong` type,
it cannot be `ref`,
and it is set to be the index of the array element.
)
--------------
Expand Down Expand Up @@ -585,7 +585,7 @@ $(H3 $(LNAME2 foreach_over_associative_arrays, Foreach over Associative Arrays))
two variables declared, the first is said to be the $(I index)
and the second is said to be the $(I value). The $(I index)
must be of the same type as the indexing type of the associative
array. It cannot be $(I ref),
array. It cannot be `ref`,
and it is set to be the index of the array element.
The order in which the elements of the array are iterated over is unspecified
for $(D foreach). $(D foreach_reverse) for associative arrays
Expand Down Expand Up @@ -835,52 +835,54 @@ void main()
that is confusing to read. Therefore, using $(D foreach_reverse) with a
delegate is now deprecated, and will be rejected in the future.)

$(H3 $(LNAME2 foreach_over_tuples, Foreach over Tuples))
$(H3 $(LNAME2 foreach_over_tuples, Foreach over Sequences))

$(P
If the aggregate expression is a tuple, there
can be one or two variables declared. If one, then the variable
is said to be the $(I value) set to the elements of the tuple,
one by one. If the type of the
variable is given, it must match the type of the tuple contents.
If it is not given, the type of the variable is set to the type
of the tuple element, which may change from iteration to iteration.
If there are
two variables declared, the first is said to be the $(I index)
and the second is said to be the $(I value). The $(I index)
must be of $(D int) or $(D uint) type, it cannot be $(I ref),
and it is set to be the index of the tuple element.
)

$(P
If the tuple is a list of types, then the foreach statement
is executed once for each type, and the value is aliased to that
If the aggregate expression is a sequence, there
can be one or two iteration symbols declared. If one, then the symbol
is an $(I element alias) of each element in the sequence in turn.
)$(P
If the sequence is a $(I TypeSeq), then the foreach statement
is executed once for each type, and the element alias is set to each
type.
)$(P
When the sequence is a $(I ValueSeq), the element alias is a variable
and is set to each value in the sequence. If the type of the
variable is given, it must match the type of the sequence contents.
If no type is given, the type of the variable is set to the type
of the sequence element, which may change from iteration to iteration.
)$(P
If there are
two symbols declared, the first is the $(I index variable)
and the second is the $(I element alias). The index
must be of `int`, `uint`, `long` or `ulong` type,
it cannot be `ref`,
and it is set to the index of each sequence element.
)

$(P Example:)
-----
import std.stdio;
import std.meta : AliasSeq;

void main()
{
alias TL = AliasSeq!(int, long, double);
alias Seq = AliasSeq!(int, "literal", main);

foreach (T; TL)
foreach (sym; Seq)
{
writeln(typeid(T));
pragma(msg, sym.stringof);
}
}
-----

$(P Prints:)
$(P Output:)

$(CONSOLE
int
long
double
"literal"
main()
)

$(P See also: $(DDSUBLINK spec/version, staticforeach, Static Foreach).)

$(H3 $(LNAME2 foreach_ref_parameters, Foreach Ref Parameters))

$(P $(D ref) can be used to update the original elements:
Expand Down