The Fortress Language Specification - CiteSeerX

foo:String → ()
baz: String → String
then the file is assumed to consist of the declaration of a single API named Blarf .
Unlike component compilation, API compilation does not shadow existing elements of a fortress. If we attempt to
compile an API with the same name as an API already defined in the resident fortress, an error is signaled and the
fortress is left unchanged. To remove an API, we must first remove all components referring to the API, and then issue
the shell command:
fortress removeApi name
A component that exports an API must provide a definition for every program construct declared in the API. For
example, because our component HelloWorld:
component HelloWorld
export Executable
run(args) = print “Hello, world!”
end
exports the API Executable, it must include a definition for the function run . The definition of run in HelloWorld
need not include declarations of the parameter type or return type of run , as these can be inferred from the definition
of API Executable.
Components are also allowed to import APIs. A component that imports an API is allowed to use any of the program
constructs declared in that API. For example, the following component imports API Zeepf and calls the function foo
declared in Zeepf :
component Blargh
import Zeepf
export Executable
run(args) = Zeepf.foo(“whatever”)
end
Component Blargh imports the API Zeepf and exports the API Executable. Its run function is defined by calling
function foo , defined in Zeepf . Note that foo must be referred to by the qualified name Zeepf.foo , to distinguish it
from other declarations of foo that are imported by or defined in Blargh. To call foo as an unqualified name, we can
write the following form of import statement:
component Blargh
import {foo} from Zeepf
export Executable
run(args) = Zeepf.foo(“whatever”)
end
In an import statement of the form:
import S from A
all names in the set of names S are imported from API A, and can be referred to as unqualified names within the
importing component. In the example above, the set of names we have imported consists of a single name: foo . If we
had instead written:
import {foo,baz} from Zeepf
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