| Overview |  |
Authors: : Ulf Wiger (ulf.wiger@ericsson.com).
This parse transform can be used to reduce compile-time dependencies in large systems.
In the old days, before records, Erlang programmers often wrote access functions for tuple data. This was tedious and error-prone. The record syntax made this easier, but since records were implemented fully in the pre-processor, a nasty compile-time dependency was introduced.
This module automates the generation of access functions for records. While this method cannot fully replace the utility of pattern matching, it does allow a fair bit of functionality on records without the need for compile-time dependencies.
Whenever record definitions need to be exported from a module,
inserting a compiler attribute,
export_records([RecName|...]) causes this transform
to lay out access functions for the exported records:
-module(foo)
-compile({parse_transform, dia_exprecs}).
-record(a, {a, b, c}).
-export_records([a]).
-export(['#info-'/1, '#info-'/2,
'#get-'/2, '#set-'/2,
'#new-a'/0, '#new-a'/1,
'#get-a'/2, '#set-a'/2,
'#info-a'/1]).
'#info-'(Rec) ->
'#info-'(Rec, fields).
'#info-'(a, Info) ->
'#info-a'(Info).
'#new-a'() -> #a{}.
'#new-a'(Vals) -> '#set-a'(Vals, #a{}).
'#get-'(Attrs, Rec) when is_record(Rec, a) ->
'#get-a'(Attrs, Rec).
'#get-a'(Attrs, R) when is_list(Attrs) ->
['#get-a'(A, R) || A <- Attrs];
'#get-a'(a, R) -> R#a.a;
'#get-a'(b, R) -> R#a.b;
'#get-a'(c, R) -> R#a.c.
'#set-'(Vals, Rec) when is_record(Rec, a) ->
'#set-a'(Vals, Rec).
'#set-a'(Vals, Rec) ->
F = fun ([], R, _F1) -> R;
([{a, V} | T], R, F1) -> F1(T, R#a{a = V}, F1);
([{b, V} | T], R, F1) -> F1(T, R#a{b = V}, F1);
([{c, V} | T], R, F1) -> F1(T, R#a{c = V}, F1)
end,
F(Vals, Rec, F).
'#info-a'(fields) -> record_info(fields, a);
'#info-a'(size) -> record_info(size, a).
| context/2 | |
| format_error/1 | |
| parse_transform/2 |
context(X1, Context) -> any()
format_error(X1) -> any()
parse_transform(Forms, Options) -> any()
Generated by EDoc, Jan 10 2010, 19:56:29.