UBF(B)
UBF(B) - quick summary
UBF(B) has:
- A type system
- Strings are written enclosed in double quotes, thus:
- A protocol description language
- The protocol description language
allows allows us to specific client server interaction in terms of a non-deterministic finite state machine.
The type system
The notation:
- int() Means a UBF(A) integer.
- string() Means a UBF(A) string.
- constant() Means a UBF(A) constant.
- bin() Means a UBF(A) binary data item.
- X() Means an Object of type X
UBF(A) literals are written as follows:
- "..." - denotes a UBF(A) string.
- [a-z][a-zA-Z0-9_]* - denotes a UBF(A) constant.
- [-][0-9]+ - denotes a UBF(A) integer.
Complex types are defined recursively:
- {T1, T2, ..., Tn}
- Is the tuple type if T1 .. Tn are types.
We say that {X1, X2, ..., Xn} is of type
{T1, T2, ..., Tn} if X1 is of type T1, X2 is of type T2, ... and
Xn is of type Tn.
- [T]
- Is the list type if T is a type.
We say that # Xn & Xn-1 & ... X2 & x1 is of type
[T] if all Xi are of type T.
- T1 | T2
- Is the alternation type if T1 and T2 are types.
We say that X is of type
T1 | T2 if X is of type T1 or if
X is of type T2.
New types
New types are introduced in UBF(B) with the notation:
+TYPE X() = Type
Examples:
+TYPE person() = {person, firstname(), lastname(), sex(), age()}.
+TYPE firstname() = string().
+TYPE lastname() = string().
+TYPE age() = int().
+TYPE sex() = male | female.
+Type people() = [person()].
This type schema defines a number of different types.
For example, it is easily seen that:
'person' >p
# {p "jim" "smith" male 10} &
# {p "susan" "jones" female 14} & $
Is of type people().
Note that UBF(B) type is a language independent type schema.
language independent type schema are the basis of Contracts
between clients are servers.
+NAME("irc").
+VSN("ubf1.0").
+TYPES
info() = info;
description() = description;
contract() = contract;
bool() = true | false;
nick() = string();
oldnick() = string();
newnick() = string();
group() = string();
logon() = logon;
proceed() = {ok, nick()} "A random nick is assigned";
listGroups() = groups;
groups() = [group()];
joinGroup() = {join, group()}
"You must join a group before you can send a message to it";
leaveGroup() = {leave, group()};
ok() = ok;
changeNick() = {nick, nick()} "Change your nick in all groups";
msg() = {msg, group(), string()} "send a message to a group";
msgEvent() = {msg, nick(), group(), string()};
joinEvent() = {joins, nick(), group()};
leaveEvent() = {leaves, nick(), group()};
changeNameEvent() = {changesName, oldnick(),newnick(), group()}.
%% I am assigned an initial (random) nick
+STATE start logon() => proceed() & active.
+STATE active
listGroups() => groups() & active;
joinGroup() => ok() & active;
leaveGroup() => ok() & active;
changeNick() => bool() & active;
msg() => bool() & active; % false if you have not joined the group
EVENT => msgEvent(); % A group sends me a message
EVENT => joinEvent(); % Nick joins group
EVENT => leaveEvent(); % Nick leaves group
EVENT => changeNameEvent(). % Nick changes name
+ANYSTATE
info() => string();
description() => string();
contract() => term().
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