Low word of signed integer multiply.

Return non-zero if there is any possibility that the upper word of a signed integer multiply might contain useful information. Return zero only if you are completely sure that no overflow can occur. On a 32-bit platform, the recommmended implementation is to do a 32 x 32 -> 64 signed multiply, and subtract result[63:32] from (result[31] >>signed 31). If this is zero, meaning that the upper word is merely a sign extension of the lower one, no overflow can occur.

On a 64-bit platform it is not always possible to acquire the top 64 bits of the result. Therefore, a recommended implementation is to take the absolute value of both operands, and return 0 iff bits[63:31] of them are zero, since that means that their magnitudes fit within 31 bits, so the magnitude of the product must fit into 62 bits.

If in doubt, return non-zero, but do make an effort to create the correct answer for small args, since otherwise the performance of (*) :: Integer -> Integer -> Integer will be poor.

Rounds towards zero.

Satisfies (quotInt# x y) *# y +# (remInt# x y) == x.

Add with carry. First member of result is (wrapped) sum; second member is 0 iff no overflow occured.

Subtract with carry. First member of result is (wrapped) difference; second member is 0 iff no overflow occured.

Shift left. Result undefined if shift amount is not in the range 0 to word size - 1 inclusive.

Shift right arithmetic. Result undefined if shift amount is not in the range 0 to word size - 1 inclusive.

Shift right logical. Result undefined if shift amount is not in the range 0 to word size - 1 inclusive.

Shift left logical. Result undefined if shift amount is not in the range 0 to word size - 1 inclusive.

Shift right logical. Result undefined if shift amount is not in the range 0 to word size - 1 inclusive.

Truncates a Double. Results are undefined if the truncation if truncation yields a value outside the range of Int#.

Exponentiation.

Convert to integer. First component of the result is -1 or 1, indicating the sign of the mantissa. The next two are the high and low 32 bits of the mantissa respectively, and the last is the exponent.

Truncates a Float. Results are undefined if the truncation if truncation yields a value outside the range of Int#.

Convert to integers. First Int# in result is the mantissa; second is the exponent.

Create a new mutable array with the specified number of elements, in the specified state thread, with each element containing the specified initial value.

Read from specified index of mutable array. Result is not yet evaluated.

Write to specified index of mutable array.

Read from specified index of immutable array. Result is packaged into an unboxed singleton; the result itself is not yet evaluated.

Make a mutable array immutable, without copying.

Make an immutable array mutable, without copying.

Create a new mutable byte array of specified size (in bytes), in the specified state thread.

Create a mutable byte array that the GC guarantees not to move.

Create a mutable byte array, aligned by the specified amount, that the GC guarantees not to move.

Intended for use with pinned arrays; otherwise very unsafe!

Make a mutable byte array immutable, without copying.

Return the size of the array in bytes.

Return the size of the array in bytes.

Read 8-bit character; offset in bytes.

Read 31-bit character; offset in 4-byte words.

Read 8-bit character; offset in bytes.

Read 31-bit character; offset in 4-byte words.

Write 8-bit character; offset in bytes.

Write 31-bit character; offset in 4-byte words.

An arbitrary machine address assumed to point outside the garbage-collected heap.

The null address.

Result is meaningless if two Addr#s are so far apart that their difference doesn't fit in an Int#.

Return the remainder when the Addr# arg, treated like an Int#, is divided by the Int# arg.

Coerce directly from address to int. Strongly deprecated.

Coerce directly from int to address. Strongly deprecated.

Reads 8-bit character; offset in bytes.

Reads 31-bit character; offset in 4-byte words.

Reads 8-bit character; offset in bytes.

Reads 31-bit character; offset in 4-byte words.

A MutVar# behaves like a single-element mutable array.

Create MutVar# with specified initial value in specified state thread.

Read contents of MutVar#. Result is not yet evaluated.

Write contents of MutVar#.

Create a new TVar# holding a specified initial value.

Read contents of TVar#. Result is not yet evaluated.

Read contents of TVar# outside an STM transaction

Write contents of TVar#.

A shared mutable variable (not the same as a MutVar#!). (Note: in a non-concurrent implementation, (MVar# a) can be represented by (MutVar# (Maybe a)).)

Create new MVar#; initially empty.

If MVar# is empty, block until it becomes full. Then remove and return its contents, and set it empty.

If MVar# is empty, immediately return with integer 0 and value undefined. Otherwise, return with integer 1 and contents of MVar#, and set MVar# empty.

If MVar# is full, block until it becomes empty. Then store value arg as its new contents.

If MVar# is full, immediately return with integer 0. Otherwise, store value arg as MVar#'s new contents, and return with integer 1.

Return 1 if MVar# is empty; 0 otherwise.

Sleep specified number of microseconds.

Block until input is available on specified file descriptor.

Block until output is possible on specified file descriptor.

State# is the primitive, unlifted type of states. It has one type parameter, thus State# RealWorld, or State# s, where s is a type variable. The only purpose of the type parameter is to keep different state threads separate. It is represented by nothing at all.

RealWorld is deeply magical. It is primitive, but it is not unlifted (hence ptrArg). We never manipulate values of type RealWorld; it's only used in the type system, to parameterise State#.

(In a non-concurrent implementation, this can be a singleton type, whose (unique) value is returned by myThreadId#. The other operations can be omitted.)

Returns the number of sparks in the local spark pool.

Primitive bytecode type.

Convert an Addr# to a followable type.

Evaluates its first argument to head normal form, and then returns its second argument as the result.

The call (inline f) arranges that f is inlined, regardless of its size. More precisely, the call (inline f) rewrites to the right-hand side of f's definition. This allows the programmer to control inlining from a particular call site rather than the definition site of the function (c.f. INLINE pragmas in User's Guide, Section 7.10.3, "INLINE and NOINLINE pragmas").

This inlining occurs regardless of the argument to the call or the size of f's definition; it is unconditional. The main caveat is that f's definition must be visible to the compiler. That is, f must be let-bound in the current scope. If no inlining takes place, the inline function expands to the identity function in Phase zero; so its use imposes no overhead.

It is good practice to mark the function with an INLINABLE pragma at its definition, (a) so that GHC guarantees to expose its unfolding regardless of size, and (b) so that you have control over exactly what is inlined.

The lazy function restrains strictness analysis a little. The call (lazy e) means the same as e, but lazy has a magical property so far as strictness analysis is concerned: it is lazy in its first argument, even though its semantics is strict. After strictness analysis has run, calls to lazy are inlined to be the identity function.

This behaviour is occasionally useful when controlling evaluation order. Notably, lazy is used in the library definition of Control.Parallel.par:

par :: a -> b -> b

par x y = case (par# x) of _ -> lazy y

If lazy were not lazy, par would look strict in y which would defeat the whole purpose of par.

Like seq, the argument of lazy can have an unboxed type.

The type constructor Any is type to which you can unsafely coerce any lifted type, and back.

• It is lifted, and hence represented by a pointer
• It does not claim to be a data type, and that's important for the code generator, because the code gen may enter a data value but never enters a function value.

It's also used to instantiate un-constrained type variables after type checking. For example

length Any []

Annoyingly, we sometimes need Anys of other kinds, such as (* -> *) etc. This is a bit like tuples. We define a couple of useful ones here, and make others up on the fly. If any of these others end up being exported into interface files, we'll get a crash; at least until we add interface-file syntax to support them.

The function unsafeCoerce# allows you to side-step the typechecker entirely. That is, it allows you to coerce any type into any other type. If you use this function, you had better get it right, otherwise segmentation faults await. It is generally used when you want to write a program that you know is well-typed, but where Haskell's type system is not expressive enough to prove that it is well typed.

The following uses of unsafeCoerce# are supposed to work (i.e. not lead to spurious compile-time or run-time crashes):

• Casting any lifted type to Any
• Casting Any back to the real type
• Casting an unboxed type to another unboxed type of the same size (but not coercions between floating-point and integral types)
• Casting between two types that have the same runtime representation. One case is when the two types differ only in "phantom" type parameters, for example Ptr Int to Ptr Float, or [Int] to [Float] when the list is known to be empty. Also, a newtype of a type T has the same representation at runtime as T.

Other uses of unsafeCoerce# are undefined. In particular, you should not use unsafeCoerce# to cast a T to an algebraic data type D, unless T is also an algebraic data type. For example, do not cast Int->Int to Bool, even if you later cast that Bool back to Int->Int before applying it. The reasons have to do with GHC's internal representation details (for the congnoscenti, data values can be entered but function closures cannot). If you want a safe type to cast things to, use Any, which is not an algebraic data type.

Emits an event via the RTS tracing framework. The contents of the event is the zero-terminated byte string passed as the first argument. The event will be emitted either to the .eventlog file, or to stderr, depending on the runtime RTS flags.