1	#!/usr/bin/env bash
2
3	#### (( )) result
4	(( 1 )) && echo True
5	(( 0 )) || echo False
6	## stdout-json: "True\nFalse\n"
7
8	#### negative number is true
9	(( -1 )) && echo True
10	## stdout: True
11
12	#### (( )) in if statement
13	if (( 3 > 2)); then
14	echo True
15	fi
16	## stdout: True
17
18	#### (( ))
19	# What is the difference with this and let? One difference: spaces are allowed.
20	(( x = 1 ))
21	(( y = x + 2 ))
22	echo $x $y
23	## stdout: 1 3
24
25	#### (( )) with arrays
26	a=(4 5 6)
27	(( sum = a[0] + a[1] + a[2] ))
28	echo $sum
29	## stdout: 15
30	## OK zsh stdout: 9
31
32	#### (( )) with error
33	(( a = 0 )) || echo false
34	(( b = 1 )) && echo true
35	(( c = -1 )) && echo true
36	echo $((a + b + c))
37	## STDOUT:
38	false
39	true
40	true
41	0
42	## END
43
44
45	#### bash and mksh: V in (( a[K] = V )) gets coerced to integer
46	K=key
47	V=value
48	typeset -a a
49	(( a[K] = V ))
50
51	# not there!
52	echo a[\"key\"]=${a[$K]}
53
54	echo keys = ${!a[@]}
55	echo values = ${a[@]}
56	## STDOUT:
57	a["key"]=0
58	keys = 0
59	values = 0
60	## END
61	## N-I zsh status: 1
62	## N-I zsh stdout-json: ""
63
64	#### bash: K in (( A[K] = V )) is a constant string
65	K=5
66	V=42
67	typeset -A A
68	(( A[K] = V ))
69
70	echo A["5"]=${A["5"]}
71	echo keys = ${!A[@]}
72	echo values = ${A[@]}
73	## STDOUT:
74	A[5]=
75	keys = K
76	values = 42
77	## END
78	## N-I zsh status: 1
79	## N-I zsh stdout-json: ""
80	## N-I mksh status: 1
81	## N-I mksh stdout-json: ""
82
83	#### BUG: (( V = A[K] )) doesn't retrieve the right value
84	typeset -A A
85	K=5
86	V=42
87	A["$K"]=$V
88	A["K"]=oops
89	A[K]=oops2
90
91	# We don't neither 42 nor "oops". Bad!
92	(( V = A[K] ))
93
94	echo V=$V
95	## status: 1
96	## stdout-json: ""
97	## BUG bash/zsh status: 0
98	## BUG bash/zsh STDOUT:
99	V=0
100	## END
101
102	#### bash: V in (( A[K] = V )) gets coerced to integer
103	K=key
104	V=value
105	typeset -A A || exit 1
106	(( A[K] = V ))
107
108	# not there!
109	echo A[\"key\"]=${A[$K]}
110
111	echo keys = ${!A[@]}
112	echo values = ${A[@]}
113	## STDOUT:
114	A["key"]=
115	keys = K
116	values = 0
117	## END
118	## N-I zsh stdout-json: ""
119	## N-I zsh status: 1
120	## N-I mksh stdout-json: ""
121	## N-I mksh status: 1
122
123	#### literal strings not properly supported
124	declare -A A
125	A['x']=x
126	(( x = A['x'] ))
127	(( A['y'] = 'y' )) # y is a variable, gets coerced to 0
128	echo $x ${A['y']}
129	## STDOUT:
130	0 0
131	## END
132	## N-I zsh/mksh STDOUT:
133	0
134	## END