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This section defines the Text interface that defines text operations.
INTERFACE Text; TYPE T = TEXT;
A non-nil TEXT represents a zero-based sequence of characters. NIL does not represent any sequence of characters, it will not be returned from any procedure in the interface, and it is a checked runtime error to pass it to any procedure in the interface.
PROCEDURE Cat(t, u: T): T;
The concatenation of t and u.
PROCEDURE Equal(t, u: T): BOOLEAN;
TRUE if t and u have the same length and (case-sensitive) contents.
PROCEDURE GetChar(t: T; i: CARDINAL): CHAR;
Character i of t. A checked runtime error if i >= Length(t).
PROCEDURE Length(t: T): CARDINAL;
The number of characters in t.
PROCEDURE Empty(t: T): BOOLEAN;
TRUE if Length(t) = 0.
PROCEDURE Sub(t: T; start, length: CARDINAL): T;
Return a subsequence of t: empty if start >= Length(t) or length = 0; otherwise, the subsequence ranging from start to the minimum of start+length-1 and Length(t)-1.
PROCEDURE SetChars(VAR a: ARRAY OF CHAR; t: T);
For each i from 0 to MIN(LAST(a), Length(t)-1), set a[i] to GetChar(t, i).
PROCEDURE FromChar(ch: CHAR): T;
A text containing the single character ch.
PROCEDURE FromChars(READONLY a: ARRAY OF CHAR): T;
A text containing the characters of a.
PROCEDURE Hash(t: T): INTEGER;
Return a hash function of the contents of t.
END Text.
If a shared variable is written concurrently by two threads, or written by one and read concurrently by another, the effect is to set the variable to an implementation-dependent value of its type. For example, if one thread writes a[0] while another concurrently writes a[1], one of the writes might be lost. Thus, portable programs must use the Thread interface to provide mutual exclusion for shared variables.
INTERFACE Thread; TYPE T <: REFANY; Mutex = MUTEX; Condition <: ROOT; Closure = OBJECT METHODS apply(): REFANY END;
A Thread.T is a handle on a thread. A Mutex is locked by some thread or unlocked. A Condition is a set of waiting threads. A newly allocated Mutex is unlocked; a newly allocated Condition is empty. It is a checked runtime error to pass the NIL Mutex, Condition or T to any procedure in this interface.
PROCEDURE Fork(cl: Closure): T;
A handle on a newly created thread executing cl.apply().
PROCEDURE Join(t: T): REFANY;
Wait until t has terminated and return its result. It is a checked error to call this more than once for any t.
PROCEDURE Wait(m: Mutex; c: Condition);
The calling thread must have m locked. Atomically unlocks m and waits on c. Then relocks m and returns.
PROCEDURE Acquire(m: Mutex);
Wait until m is unlocked and then lock it.
PROCEDURE Release(m: Mutex);
The calling thread must have m locked. Unlocks m.
PROCEDURE Broadcast(c: Condition);
All threads waiting on c become eligible to run.
PROCEDURE Signal(c: Condition);
One or more threads waiting on c become eligible to run.
PROCEDURE Self(): T;
Return the handle of the calling thread.
EXCEPTION Alerted;
Used to approximate asynchronous interrupts.
PROCEDURE Alert(t: T);
Mark t as an alerted thread.
PROCEDURE TestAlert(): BOOLEAN;
TRUE if the calling thread has been marked alerted.
PROCEDURE AlertWait(m: Mutex; c: Condition) RAISES {Alerted};
Like Wait, but if the thread is marked alerted at the time of call or sometime during the wait, lock m and raise Alerted.
PROCEDURE AlertJoin(t: T): REFANY RAISES {Alerted};
Like Join, but if the calling thread is marked alerted at the time of call or sometime during the wait, raise Alerted.
CONST AtomicSize = ...;
An implementation-dependent integer constant: the number of bits in a memory-coherent block. If two components of a record or array fall in different blocks, they can be accessed concurrently by different threads without locking.
END Thread.
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