| rev |
line source |
|
jbe@0
|
1 seqlua: Extended sequences and iterators in Lua
|
|
jbe@0
|
2 ===============================================
|
|
jbe@0
|
3
|
|
jbe@0
|
4 This is an experimental package to extend Lua in the following manner:
|
|
jbe@0
|
5
|
|
jbe@0
|
6 * allow ipairs(...) to accept tables as well as functions or iterator triplets,
|
|
jbe@0
|
7 * provide a function iterator(...) that returns single functions unmodified,
|
|
jbe@0
|
8 but converts
|
|
jbe@0
|
9 * iterator triplets into closures, and
|
|
jbe@0
|
10 * tables into a function closure that iterates over the elements,
|
|
jbe@0
|
11 * provide the auxiliary C functions and macros to simplify iterating over both
|
|
jbe@0
|
12 tables and iterator functions with the same statement.
|
|
jbe@0
|
13
|
|
jbe@0
|
14 This library completely ignores the ``__ipairs`` metamethod (as it is
|
|
jbe@0
|
15 deprecated since Lua 5.3.0-alpha). It respects, however, any ``__call``
|
|
jbe@0
|
16 metamethods (this may cause unexpected behavior when passing callable tables
|
|
jbe@0
|
17 to ``ipairs``).
|
|
jbe@0
|
18
|
|
jbe@0
|
19
|
|
jbe@0
|
20
|
|
jbe@0
|
21 Lua part of the library
|
|
jbe@0
|
22 -----------------------
|
|
jbe@0
|
23
|
|
jbe@0
|
24 The new ``ipairs(...)`` function works as follows:
|
|
jbe@0
|
25
|
|
jbe@0
|
26 require "seqlua"
|
|
jbe@0
|
27
|
|
jbe@0
|
28 t = {"a", "b", "c"}
|
|
jbe@0
|
29
|
|
jbe@0
|
30 for i, v in ipairs(t) do
|
|
jbe@0
|
31 print(i, v)
|
|
jbe@0
|
32 end
|
|
jbe@0
|
33 -- prints:
|
|
jbe@0
|
34 -- 1 a
|
|
jbe@0
|
35 -- 2 b
|
|
jbe@0
|
36 -- 3 c
|
|
jbe@0
|
37
|
|
jbe@0
|
38 function alphabet()
|
|
jbe@0
|
39 local letter = nil
|
|
jbe@0
|
40 return function()
|
|
jbe@0
|
41 if letter == nil then
|
|
jbe@0
|
42 letter = "a"
|
|
jbe@0
|
43 elseif letter == "z" then
|
|
jbe@0
|
44 return nil
|
|
jbe@0
|
45 else
|
|
jbe@0
|
46 letter = string.char(string.byte(letter) + 1)
|
|
jbe@0
|
47 end
|
|
jbe@0
|
48 return letter
|
|
jbe@0
|
49 end
|
|
jbe@0
|
50 end
|
|
jbe@0
|
51
|
|
jbe@0
|
52 f = alphabet()
|
|
jbe@0
|
53
|
|
jbe@0
|
54 for i, v in ipairs(f) do
|
|
jbe@0
|
55 print(i, v)
|
|
jbe@0
|
56 end
|
|
jbe@0
|
57 -- prints:
|
|
jbe@0
|
58 -- 1 a
|
|
jbe@0
|
59 -- 2 b
|
|
jbe@0
|
60 -- 3 c
|
|
jbe@0
|
61 -- ...
|
|
jbe@0
|
62 -- 25 y
|
|
jbe@0
|
63 -- 26 z
|
|
jbe@0
|
64
|
|
jbe@0
|
65 set = {apple = true, banana = true}
|
|
jbe@0
|
66 for i, k, v in ipairs(pairs(set)) do
|
|
jbe@0
|
67 print(i, k, v)
|
|
jbe@0
|
68 end
|
|
jbe@0
|
69 -- prints:
|
|
jbe@0
|
70 -- 1 banana true
|
|
jbe@0
|
71 -- 2 apple true
|
|
jbe@0
|
72 -- (order of "apple" and "banana" may vary)
|
|
jbe@0
|
73
|
|
jbe@0
|
74 The function ``iterator(...)`` may be used to convert any table, any function,
|
|
jbe@0
|
75 or any iterator triplet into a single function (possibly creating a closure):
|
|
jbe@0
|
76
|
|
jbe@0
|
77 function filter_strings(...)
|
|
jbe@0
|
78 nextvalue = iterator(...)
|
|
jbe@0
|
79 return function()
|
|
jbe@0
|
80 local value
|
|
jbe@0
|
81 repeat
|
|
jbe@0
|
82 value = nextvalue()
|
|
jbe@0
|
83 until value == nil or type(value) == "string"
|
|
jbe@0
|
84 return value
|
|
jbe@0
|
85 end
|
|
jbe@0
|
86 end
|
|
jbe@0
|
87
|
|
jbe@0
|
88 for i, v in ipairs(filter_strings{"Hello", true, "World"}) do
|
|
jbe@0
|
89 print(i, v)
|
|
jbe@0
|
90 end
|
|
jbe@0
|
91 -- prints:
|
|
jbe@0
|
92 -- 1 Hello
|
|
jbe@0
|
93 -- 2 World
|
|
jbe@0
|
94
|
|
jbe@0
|
95 tbl = {apple = true, banana = true, [1] = "array entry"}
|
|
jbe@0
|
96 for v in filter_strings(pairs(tbl)) do
|
|
jbe@0
|
97 print(v)
|
|
jbe@0
|
98 end
|
|
jbe@0
|
99 -- prints:
|
|
jbe@0
|
100 -- banana
|
|
jbe@0
|
101 -- apple
|
|
jbe@0
|
102 -- (order may vary)
|
|
jbe@0
|
103
|
|
jbe@0
|
104
|
|
jbe@0
|
105
|
|
jbe@0
|
106 C part of the library
|
|
jbe@0
|
107 ---------------------
|
|
jbe@0
|
108
|
|
jbe@0
|
109 In ``seqlualib.h``, the following macro is defined:
|
|
jbe@0
|
110
|
|
jbe@0
|
111 #define seqlua_iterloop(L, iter, idx) \
|
|
jbe@0
|
112 for ( \
|
|
jbe@0
|
113 seqlua_iterinit((L), (iter), (idx)); \
|
|
jbe@0
|
114 seqlua_iternext(iter); \
|
|
jbe@0
|
115 lua_pop((L), 1) \
|
|
jbe@0
|
116 )
|
|
jbe@0
|
117
|
|
jbe@0
|
118 This macro allows iteration over either tables or iterator functions (but not
|
|
jbe@0
|
119 iterator triplets) as the following example function demonstrates:
|
|
jbe@0
|
120
|
|
jbe@0
|
121 int printcsv(lua_State *L) {
|
|
jbe@0
|
122 seqlua_Iterator iter;
|
|
jbe@0
|
123 seqlua_iterloop(L, &iter, 1) {
|
|
jbe@0
|
124 if (seqlua_itercount(&iter) > 1) fputs(",", stdout);
|
|
jbe@0
|
125 fputs(luaL_tolstring(L, -1, NULL), stdout);
|
|
jbe@1
|
126 lua_pop(L, 1); // pops value that luaL_tolstring pushed onto stack
|
|
jbe@0
|
127 }
|
|
jbe@0
|
128 fputs("\n", stdout);
|
|
jbe@0
|
129 return 0;
|
|
jbe@0
|
130 }
|
|
jbe@0
|
131
|
|
jbe@0
|
132 printcsv{"a", "b", "c"} -- prints: a,b,c
|
|
jbe@0
|
133
|
|
jbe@0
|
134 Additionally, ``seqlualib`` includes a function ``seqlua_iterclosure(L, idx)``,
|
|
jbe@0
|
135 which converts a table at a given stack index into a function closure (stored
|
|
jbe@0
|
136 on the same stack index) that iterates over the elements of the table. If the
|
|
jbe@0
|
137 value at the given stack index is already a function, it leaves the value
|
|
jbe@0
|
138 unchanged. If the value is convertible to a function using ``__ipairs,`` then
|
|
jbe@0
|
139 the function is replaced by its ``__ipairs`` metamethod.
|
|
jbe@0
|
140
|
|
jbe@0
|
141
|