Revision 28664

Date:
2009/10/08 20:49:07
Author:
jnthn
Revision Log:
First cut of specification for signature introspection.
Files:

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  • docs/Perl6/Spec/S06-routines.pod

     
    1924 1924
    1925 1925 =back
    1926 1926
    1927 =head2 Signature Introspection
    1927 1928
    1929 A C<Signature> object can be introspected to find out the details of
    1930 the parameters it is defined as expected. The C<.params> method will
    1931 return a C<List> of C<Parameter> objects, which have the following
    1932 readonly properties:
    1933
    1934 name The name of the lexical variable to bind to, if any
    1935 type The main type (the one multi-dispatch sorts by)
    1936 constraints Any further type constraints
    1937 readonly True if parameter has C<is readonly> trait
    1938 rw True if parameter has C<is rw> trait
    1939 copy True if parameter has C<is copy> trait
    1940 ref True if parameter has C<is ref> trait
    1941 named True if the parameter is to be passed named
    1942 named_names List of names a named parameter can be passed as
    1943 slurpy True if the parameter is slurpy
    1944 optional True if the parameter is optional
    1945 default A closure returning the default value
    1946 signature A nested signature to bind the argument against
    1947
    1948 Note that C<constraints> will be something that can be smart-matched
    1949 against if it is defined; if there are many constraints it may be a
    1950 C<Junction> of some sort, but if there is just one it may be simply
    1951 that one thing.
    1952
    1953 Further, various things that appear in an original written signature
    1954 will have been deconstructed a bit. For example, a signature like:
    1955
    1956 :(1)
    1957
    1958 Will introspect the same was as:
    1959
    1960 :(Int $ where 1)
    1961
    1962 And if we have:
    1963
    1964 subset Odd of Int where { $^n % 2 };
    1965 sub foo(Odd $x) { ... }
    1966
    1967 Then the signature of foo will be equivalent to something like:
    1968
    1969 :(Int $x where { $^n % 2 })
    1970
    1971 That is, the refinement type will have been deconstructed into the
    1972 part that nominal type that multiple dispatch uses for sorting the
    1973 candidates and an additional constraint.
    1974
    1975
    1928 1976 =head1 Advanced subroutine features
    1929 1977
    1930 1978 =head2 The C<return> function