Changeset 2335

Timestamp:

03/20/10 04:42:28 (23 months ago)

Author:

Chuck.Esterbrook

Message:

Improvements to the How-To's.

Location:

cobra/trunk/HowTo

Files:

cobra/trunk/HowTo/101-WriteBasicSyntax.cobra

r2127	r2335
52	52
53	53	# If-else statement
	54	# See also: "Make An If Else Ladder" How To
54	55	if a > b
55	56	print 'a is greater'
…	…
57	58	print 'a is not greater'
58	59
59		# Can put target on same if target is just one statement
	60	# Can put target on same line if the target is just one statement
60	61	if a > b, print 'a is greater'
61	62	else, print 'b is greater or equal'
…	…
64	65	while a > b
65	66	a -= 1 # augmented assignment
	67
	68	# While loop in one line
66	69	while a > b, a -= 1
	70
	71	# Parallel assignment
	72	a, b = 1, 2
	73
	74	# Lists -- see the "Use Lists" How To for more info
	75	t = ['a', 'b', 'c']
	76	for letter in t, print letter
	77
	78	# Dictionaries
	79	d = {'a': 1, 'b': 2}
	80	assert d['a'] == 1 and d['b'] == 2
	81	for key, value in d
	82	print '[key] = [value]' # string interpolation
	83
	84	# Sets -- like lists, but no repetition
	85	letters = {'a', 'b', 'c'}
	86	assert 'a' in letters
	87	for letter in letters, print letter
67	88
68	89	# Line continuation is implicit with parenthesized arguments

r2127	r2335
44	44
45	45	# Many properties just cover for an underlying variable. When that
46		# is the case, you can use a shortcut syntaxes. Later, you can
	46	# is the case, you can use a shortcut syntax. Later, you can
47	47	# change the property to the full form in order to add logic.
48	48
…	…
61	61
62	62
	63	# You can even pack an initial value into the declaration
	64	# which also be used to infer the data type.
	65
	66	class Person3
	67
	68	pro name from var = '' # inferred as String
	69
	70	pro age from var = 0 # inferred as int
	71
	72
63	73	# In this shortcut syntax, the vars were already declared so
64	74	# the property simply "... from var":
65	75
66		class Person3
	76	class Person4
67	77
68	78	var _name as String
…	…
88	98	# you can specify that name instead of "var":
89	99
90		class Person4
	100	class Person5
91	101
92	102	var _name as String
…	…
101	111	# Properties can be read-only:
102	112
103		class Person5
	113	class Person6
104	114
105	115	cue init(name as String)

r2127	r2335
8	8	* Use the `branch` statement (see MakeABranchStatement.cobra)
9	9
10		When using an if-else ladder, consider ~~rais~~ing a FallThroughException() at the
	10	When using an if-else ladder, consider throwing a FallThroughException() at the
11	11	bottom if you expect that it should never happen.
12	12

r2127	r2335
84	84	assert word == 'number'
85	85
86		# ~~Don't forget that you can~~ branch on enumerations, strings and characters.
	86	# You can also branch on enumerations, strings and characters.

r2127	r2335
8	8
9	9	cue init
10		# ~~code~~
	10	# statements
11	11
12	12	cue init(ARG as TYPE)
13		# ~~code~~
	13	# statements
14	14
15	15	cue init(ARG1 as TYPE1, ARG2 as TYPE2)
16		# code
	16	# statements
	17
	18	Where the first statement is call to another initializer in the same class or
	19	the base class:
17	20
18	21	Some key points:
…	…
20	23	* You can have 0 or more arguments.
21	24
22		* If you declare no initalizers at all for a given class, Cobra will
23		provide one, public, parameterless initializer.
	25	* If you declare no initializers at all, Cobra will automatically provide
	26	them to match each non-private initializer in the base class.
	27
	28	* If you declare even one initializer, Cobra will not automatically add any
	29	more. This gives you control over how a class must be initialized.
24	30
25	31	* Initializers can be overloaded by the number and type of their arguments.
…	…
27	33	* Initializers are public by default.
28	34
29		* Initializers can say "base.init(ARGS)" to invoke a base init.
	35	* Initializers can say "base.init" or "base.init(ARGS)" to invoke
	36	a base initializer.
30	37
31		* Initializers can say ".init" or ".init(ARGS)" to invoke a fellow init.
	38	* Initializers can say ".init" or ".init(ARGS)" to invoke
	39	a fellow initialier.
32	40
33	41	* Initializers can have their own unit tests just like methods.
…	…
94	102	get age from var as int
95	103
	104
	105	class Program
	106
96	107	def main
97	108	pass

r2216	r2335
230	230	assert names.indexOf('foo', 1, 2) == -1 # start at 1, search 2 items
231	231
232		# left off on .insertRange
	232	# TODO: left off on .insertRange
233	233
234	234	# additional methods. search web for "msdn generic list"
…	…
269	269	require .count > 0
270	270	return this[.count // 2]
	271
271	272
272	273	# a subclass with specific type
…	…
289	290	return leftMost
290	291
	292
291	293	# a generic subclass with a type constraint is even better,
292	294	# because then you can specify a type parameter when using it

r2046	r2335
53	53	body
54	54	sum = 0
55		for num in nums
56		sum += num
	55	for num in nums, sum += num
57	56	return sum
58	57
…	…
61	60	# list or any object that implements IList.
62	61	sum = 0
63		for num in nums
64		sum += num
	62	for num in nums, sum += num
65	63	return sum
66	64

r2127	r2335
92	92	name = if(value and value <> 0, 'value', nil) # type is "String?"
93	93	if name, print name
	94
	95	# you can coalesce with ? as a binary operator
	96	displayName = name ? '(no name)'
	97	print displayName

r2127	r2335
47	47	for cust in customers, print cust
48	48
49		# Yes, there will be lambdas in a future version so
50		# the comparison can be inlined in the sort() call.
	49	# you can localize the comparison code with a closure
	50	customers.sort(do(a as Customer, b as Customer))
	51	return a.name.toLower.compareTo(b.name.toLower)
	52
	53	# or a lambda expression
	54	customers.sort(do(a as Customer, b as Customer)=a.name.toLower.compareTo(b.name.toLower))
51	55
52	56	def orderByName(a as Customer, b as Customer) as int is shared

r2127	r2335
37	37	def dump
38	38	print this stop
39		if _left
40		print ' left:', _left stop
41		if _right
42		print ' right:', _right stop
	39	if _left, print ' left:', _left stop
	40	if _right, print ' right:', _right stop
43	41	print
44	42	if _left, _left.dump

r2127	r2335
2	2	MakeACollectionClass.cobra
3	3
4		This HowTo shows the syntax and techniques for declaring an IList.
	4	This HowTo shows the syntax and techniques for declaring a class that
	5	implements IList<of T>.
5	6	"""
6	7