seqlua
view README @ 23:29792283522f
Removed iterator(...) function; ipairs doesn't accept iterator triplets anymore
| author | jbe |
|---|---|
| date | Thu Aug 21 20:01:52 2014 +0200 (2014-08-21) |
| parents | 50c6388d4963 |
| children | 44880bcfc323 |
line source
1 seqlua: Extended sequences and iterators in Lua
2 ===============================================
4 This is an experimental package to extend Lua in the following manner:
6 * allow ipairs(...) to accept tables as well as functions
7 * provide auxiliary C functions and macros to simplify iterating over both
8 tables and iterator functions with the same statement.
10 This library completely ignores the ``__ipairs`` metamethod (as it is
11 deprecated since Lua 5.3.0-alpha). It respects, however, any ``__index`` and
12 ``__call`` metamethods (this may cause unexpected behavior when passing
13 callable tables to ``ipairs``). The ``__call`` metamethod takes precedence over
14 an existing ``__index`` metamethod.
18 Lua part of the library
19 -----------------------
21 The new ``ipairs(...)`` function works as follows:
23 require "seqlua"
25 t = {"a", "b", "c"}
27 for i, v in ipairs(t) do
28 print(i, v)
29 end
30 -- prints:
31 -- 1 a
32 -- 2 b
33 -- 3 c
35 function alphabet()
36 local letter = nil
37 return function()
38 if letter == nil then
39 letter = "a"
40 elseif letter == "z" then
41 return nil
42 else
43 letter = string.char(string.byte(letter) + 1)
44 end
45 return letter
46 end
47 end
49 for i, v in ipairs(alphabet()) do
50 print(i, v)
51 end
52 -- prints:
53 -- 1 a
54 -- 2 b
55 -- 3 c
56 -- ...
57 -- 25 y
58 -- 26 z
60 function filter(f, seq)
61 return coroutine.wrap(function()
62 for i, v in ipairs(seq) do f(v) end
63 end)
64 end
66 function filterfunc(v)
67 local type_v = type(v)
68 if type_v == "string" then
69 coroutine.yield(v)
70 elseif type_v == "number" then
71 for i = 1, v do
72 coroutine.yield(true)
73 end
74 end
75 end
77 for v in filter(filterfunc, {"a", "b", 3, "c"}) do
78 print(v)
79 end
80 -- prints:
81 -- a
82 -- b
83 -- true
84 -- true
85 -- true
86 -- c
89 C part of the library
90 ---------------------
92 In ``seqlualib.h``, the following macro is defined:
94 #define seqlua_iterloop(L, iter, idx) \
95 for ( \
96 seqlua_iterinit((L), (iter), (idx)); \
97 seqlua_iternext(iter); \
98 lua_pop((L), 1) \
99 )
101 This macro allows iteration over either tables or iterator functions as the
102 following example function demonstrates:
104 int printcsv(lua_State *L) {
105 seqlua_Iterator iter;
106 seqlua_iterloop(L, &iter, 1) {
107 if (seqlua_itercount(&iter) > 1) fputs(",", stdout);
108 fputs(luaL_tolstring(L, -1, NULL), stdout);
109 lua_pop(L, 1); // pops value that luaL_tolstring pushed onto stack
110 }
111 fputs("\n", stdout);
112 return 0;
113 }
115 printcsv{"a", "b", "c"}
116 -- prints: a,b,c
118 printcsv(assert(io.open("testfile")):lines())
119 -- prints: line1,line2,... of "testfile"