Description
This command declares a function.
Command Syntax
'@x:func' <id> {'[' <func formals> ']'}? {'(' <func formals> ')'}? {'~' <exp>}?
<func formals> ::=
<func formals> ::=
'%' <id>
<func formals> ::=
{<func formal> ','}* <func formal>
<func formal> ::=
<id> {'~' <exp>}?
The following options are permitted.
| lhs | This function is a left-hand-side function that can be called from the left-hand-side of assignments. There must also be a rhs function with the same name declared in the same scope. Only one of lhs and rhs can be specified on a single function. |
| rhs | This function is a left-hand-side function that can be called from the left-hand-side of assignments. There must also be a rhs function with the same name declared in the same scope. Only one of lhs and rhs can be specified on a single function. |
| visible | The function name is declared as visible in the enclosing scope. If visible is specified, then local can not be specified. For lhs-rhs function pairs either both or neither must be visible. |
| local | The function name is declared as local in the enclosing scope. If local is specified, then visible can not be specified. For lhs-rhs function pairs either both or neither must be local. The local option is only used for names declared directly within @x:type, @x:view and @x:view commands. |
Name Semantics
The func name is declared the scope that surrounds the @x:func command. The func formal <id>s are declared within the @x:func command scope.
Execution Semantics
Execution of the @x:func command associates the function value with the instance of the function name. The result of execution of the @x:func command is null. The body of the function is executed only when the function is called. A function can no longer be called after the scope containing the function command exits.
Examples
@x:func fact(n) {
@x:if n == 0 {
1
} @x:else {
n * fact(n - 1)
}
}
@x:for i := 1..10 {
@x:const j := fact(i);
"fact(&i;)=&j;&eol;"
}
@x:func sum[t](a~t,
a + b
}
sum[int](2,
sum[float](2.3,
See curry example.