1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
|
--- Manipulating iterators as sequences.
-- See @{07-functional.md.Sequences|The Guide}
--
-- Dependencies: `pl.utils`, `pl.types`, `debug`
-- @module pl.seq
local next,assert,pairs,tonumber,type,setmetatable = next,assert,pairs,tonumber,type,setmetatable
local strfind,format = string.find,string.format
local mrandom = math.random
local tsort,tappend = table.sort,table.insert
local io = io
local utils = require 'pl.utils'
local callable = require 'pl.types'.is_callable
local function_arg = utils.function_arg
local assert_arg = utils.assert_arg
local debug = require 'debug'
local seq = {}
-- given a number, return a function(y) which returns true if y > x
-- @param x a number
function seq.greater_than(x)
return function(v)
return tonumber(v) > x
end
end
-- given a number, returns a function(y) which returns true if y < x
-- @param x a number
function seq.less_than(x)
return function(v)
return tonumber(v) < x
end
end
-- given any value, return a function(y) which returns true if y == x
-- @param x a value
function seq.equal_to(x)
if type(x) == "number" then
return function(v)
return tonumber(v) == x
end
else
return function(v)
return v == x
end
end
end
--- given a string, return a function(y) which matches y against the string.
-- @param s a string
function seq.matching(s)
return function(v)
return strfind(v,s)
end
end
local nexti
--- sequence adaptor for a table. Note that if any generic function is
-- passed a table, it will automatically use seq.list()
-- @param t a list-like table
-- @usage sum(list(t)) is the sum of all elements of t
-- @usage for x in list(t) do...end
function seq.list(t)
assert_arg(1,t,'table')
if not nexti then
nexti = ipairs{}
end
local key,value = 0
return function()
key,value = nexti(t,key)
return value
end
end
--- return the keys of the table.
-- @param t an arbitrary table
-- @return iterator over keys
function seq.keys(t)
assert_arg(1,t,'table')
local key
return function()
key = next(t,key)
return key
end
end
local list = seq.list
local function default_iter(iter)
if type(iter) == 'table' then return list(iter)
else return iter end
end
seq.iter = default_iter
--- create an iterator over a numerical range. Like the standard Python function xrange.
-- @param start a number
-- @param finish a number greater than start
function seq.range(start,finish)
local i = start - 1
return function()
i = i + 1
if i > finish then return nil
else return i end
end
end
-- count the number of elements in the sequence which satisfy the predicate
-- @param iter a sequence
-- @param condn a predicate function (must return either true or false)
-- @param optional argument to be passed to predicate as second argument.
-- @return count
function seq.count(iter,condn,arg)
local i = 0
seq.foreach(iter,function(val)
if condn(val,arg) then i = i + 1 end
end)
return i
end
--- return the minimum and the maximum value of the sequence.
-- @param iter a sequence
-- @return minimum value
-- @return maximum value
function seq.minmax(iter)
local vmin,vmax = 1e70,-1e70
for v in default_iter(iter) do
v = tonumber(v)
if v < vmin then vmin = v end
if v > vmax then vmax = v end
end
return vmin,vmax
end
--- return the sum and element count of the sequence.
-- @param iter a sequence
-- @param fn an optional function to apply to the values
function seq.sum(iter,fn)
local s = 0
local i = 0
for v in default_iter(iter) do
if fn then v = fn(v) end
s = s + v
i = i + 1
end
return s,i
end
--- create a table from the sequence. (This will make the result a List.)
-- @param iter a sequence
-- @return a List
-- @usage copy(list(ls)) is equal to ls
-- @usage copy(list {1,2,3}) == List{1,2,3}
function seq.copy(iter)
local res,k = {},1
for v in default_iter(iter) do
res[k] = v
k = k + 1
end
setmetatable(res, require('pl.List'))
return res
end
--- create a table of pairs from the double-valued sequence.
-- @param iter a double-valued sequence
-- @param i1 used to capture extra iterator values
-- @param i2 as with pairs & ipairs
-- @usage copy2(ipairs{10,20,30}) == {{1,10},{2,20},{3,30}}
-- @return a list-like table
function seq.copy2 (iter,i1,i2)
local res,k = {},1
for v1,v2 in iter,i1,i2 do
res[k] = {v1,v2}
k = k + 1
end
return res
end
--- create a table of 'tuples' from a multi-valued sequence.
-- A generalization of copy2 above
-- @param iter a multiple-valued sequence
-- @return a list-like table
function seq.copy_tuples (iter)
iter = default_iter(iter)
local res = {}
local row = {iter()}
while #row > 0 do
tappend(res,row)
row = {iter()}
end
return res
end
--- return an iterator of random numbers.
-- @param n the length of the sequence
-- @param l same as the first optional argument to math.random
-- @param u same as the second optional argument to math.random
-- @return a sequence
function seq.random(n,l,u)
local rand
assert(type(n) == 'number')
if u then
rand = function() return mrandom(l,u) end
elseif l then
rand = function() return mrandom(l) end
else
rand = mrandom
end
return function()
if n == 0 then return nil
else
n = n - 1
return rand()
end
end
end
--- return an iterator to the sorted elements of a sequence.
-- @param iter a sequence
-- @param comp an optional comparison function (comp(x,y) is true if x < y)
function seq.sort(iter,comp)
local t = seq.copy(iter)
tsort(t,comp)
return list(t)
end
--- return an iterator which returns elements of two sequences.
-- @param iter1 a sequence
-- @param iter2 a sequence
-- @usage for x,y in seq.zip(ls1,ls2) do....end
function seq.zip(iter1,iter2)
iter1 = default_iter(iter1)
iter2 = default_iter(iter2)
return function()
return iter1(),iter2()
end
end
--- Makes a table where the key/values are the values and value counts of the sequence.
-- This version works with 'hashable' values like strings and numbers.
-- `pl.tablex.count_map` is more general.
-- @param iter a sequence
-- @return a map-like table
-- @return a table
-- @see pl.tablex.count_map
function seq.count_map(iter)
local t = {}
local v
for s in default_iter(iter) do
v = t[s]
if v then t[s] = v + 1
else t[s] = 1 end
end
return setmetatable(t, require('pl.Map'))
end
-- given a sequence, return all the unique values in that sequence.
-- @param iter a sequence
-- @param returns_table true if we return a table, not a sequence
-- @return a sequence or a table; defaults to a sequence.
function seq.unique(iter,returns_table)
local t = seq.count_map(iter)
local res,k = {},1
for key in pairs(t) do res[k] = key; k = k + 1 end
table.sort(res)
if returns_table then
return res
else
return list(res)
end
end
--- print out a sequence iter with a separator.
-- @param iter a sequence
-- @param sep the separator (default space)
-- @param nfields maximum number of values per line (default 7)
-- @param fmt optional format function for each value
function seq.printall(iter,sep,nfields,fmt)
local write = io.write
if not sep then sep = ' ' end
if not nfields then
if sep == '\n' then nfields = 1e30
else nfields = 7 end
end
if fmt then
local fstr = fmt
fmt = function(v) return format(fstr,v) end
end
local k = 1
for v in default_iter(iter) do
if fmt then v = fmt(v) end
if k < nfields then
write(v,sep)
k = k + 1
else
write(v,'\n')
k = 1
end
end
write '\n'
end
-- return an iterator running over every element of two sequences (concatenation).
-- @param iter1 a sequence
-- @param iter2 a sequence
function seq.splice(iter1,iter2)
iter1 = default_iter(iter1)
iter2 = default_iter(iter2)
local iter = iter1
return function()
local ret = iter()
if ret == nil then
if iter == iter1 then
iter = iter2
return iter()
else return nil end
else
return ret
end
end
end
--- return a sequence where every element of a sequence has been transformed
-- by a function. If you don't supply an argument, then the function will
-- receive both values of a double-valued sequence, otherwise behaves rather like
-- tablex.map.
-- @param fn a function to apply to elements; may take two arguments
-- @param iter a sequence of one or two values
-- @param arg optional argument to pass to function.
function seq.map(fn,iter,arg)
fn = function_arg(1,fn)
iter = default_iter(iter)
return function()
local v1,v2 = iter()
if v1 == nil then return nil end
return fn(v1,arg or v2) or false
end
end
--- filter a sequence using a predicate function.
-- @param iter a sequence of one or two values
-- @param pred a boolean function; may take two arguments
-- @param arg optional argument to pass to function.
function seq.filter (iter,pred,arg)
pred = function_arg(2,pred)
return function ()
local v1,v2
while true do
v1,v2 = iter()
if v1 == nil then return nil end
if pred(v1,arg or v2) then return v1,v2 end
end
end
end
--- 'reduce' a sequence using a binary function.
-- @func fn a function of two arguments
-- @param iter a sequence
-- @param initval optional initial value
-- @usage seq.reduce(operator.add,seq.list{1,2,3,4}) == 10
-- @usage seq.reduce('-',{1,2,3,4,5}) == -13
function seq.reduce (fn,iter,initval)
fn = function_arg(1,fn)
iter = default_iter(iter)
local val = initval or iter()
if val == nil then return nil end
for v in iter do
val = fn(val,v)
end
return val
end
--- take the first n values from the sequence.
-- @param iter a sequence of one or two values
-- @param n number of items to take
-- @return a sequence of at most n items
function seq.take (iter,n)
iter = default_iter(iter)
return function()
if n < 1 then return end
local val1,val2 = iter()
if not val1 then return end
n = n - 1
return val1,val2
end
end
--- skip the first n values of a sequence
-- @param iter a sequence of one or more values
-- @param n number of items to skip
function seq.skip (iter,n)
n = n or 1
for i = 1,n do
if iter() == nil then return list{} end
end
return iter
end
--- a sequence with a sequence count and the original value.
-- enum(copy(ls)) is a roundabout way of saying ipairs(ls).
-- @param iter a single or double valued sequence
-- @return sequence of (i,v), i = 1..n and v is from iter.
function seq.enum (iter)
local i = 0
iter = default_iter(iter)
return function ()
local val1,val2 = iter()
if not val1 then return end
i = i + 1
return i,val1,val2
end
end
--- map using a named method over a sequence.
-- @param iter a sequence
-- @param name the method name
-- @param arg1 optional first extra argument
-- @param arg2 optional second extra argument
function seq.mapmethod (iter,name,arg1,arg2)
iter = default_iter(iter)
return function()
local val = iter()
if not val then return end
local fn = val[name]
if not fn then error(type(val).." does not have method "..name) end
return fn(val,arg1,arg2)
end
end
--- a sequence of (last,current) values from another sequence.
-- This will return S(i-1),S(i) if given S(i)
-- @param iter a sequence
function seq.last (iter)
iter = default_iter(iter)
local val, l = iter(), nil
if val == nil then return list{} end
return function ()
val,l = iter(),val
if val == nil then return nil end
return val,l
end
end
--- call the function on each element of the sequence.
-- @param iter a sequence with up to 3 values
-- @param fn a function
function seq.foreach(iter,fn)
fn = function_arg(2,fn)
for i1,i2,i3 in default_iter(iter) do fn(i1,i2,i3) end
end
---------------------- Sequence Adapters ---------------------
local SMT
local function SW (iter,...)
if callable(iter) then
return setmetatable({iter=iter},SMT)
else
return iter,...
end
end
-- can't directly look these up in seq because of the wrong argument order...
local map,reduce,mapmethod = seq.map, seq.reduce, seq.mapmethod
local overrides = {
map = function(self,fun,arg)
return map(fun,self,arg)
end,
reduce = function(self,fun,initval)
return reduce(fun,self,initval)
end
}
SMT = {
__index = function (tbl,key)
local fn = overrides[key] or seq[key]
if fn then
return function(sw,...) return SW(fn(sw.iter,...)) end
else
return function(sw,...) return SW(mapmethod(sw.iter,key,...)) end
end
end,
__call = function (sw)
return sw.iter()
end,
}
setmetatable(seq,{
__call = function(tbl,iter,extra)
if not callable(iter) then
if type(iter) == 'table' then iter = seq.list(iter)
else return iter
end
end
if extra then
return setmetatable({iter=function()
return iter(extra)
end},SMT)
else
return setmetatable({iter=iter},SMT)
end
end
})
--- create a wrapped iterator over all lines in the file.
-- @param f either a filename, file-like object, or 'STDIN' (for standard input)
-- @param ... for Lua 5.2 only, optional format specifiers, as in `io.read`.
-- @return a sequence wrapper
function seq.lines (f,...)
local iter,obj
if f == 'STDIN' then
f = io.stdin
elseif type(f) == 'string' then
iter,obj = io.lines(f,...)
elseif not f.read then
error("Pass either a string or a file-like object",2)
end
if not iter then
iter,obj = f:lines(...)
end
if obj then -- LuaJIT version returns a function operating on a file
local lines,file = iter,obj
iter = function() return lines(file) end
end
return SW(iter)
end
function seq.import ()
debug.setmetatable(function() end,{
__index = function(tbl,key)
local s = overrides[key] or seq[key]
if s then return s
else
return function(s,...) return seq.mapmethod(s,key,...) end
end
end
})
end
return seq
|