Collections

2 min read, 255 words collectionsetsvectorslists

How to ....?

1. declare?
2. add to?
3. remove from?
4. check is exists?
5. merge into?
6. can they nest?

Sets

just like maths, unordered with no duplicates

(def players #{"Alice", "Bob", "Kelly"})
(conj players "Fred")
(disj players "Bob" "Sal")
(contains? players "Kelly")

Merge one collection INTO another collection?

(def players #{"Alice" "Bob" "Kelly"})
(def new-players ["Tim" "Sue" "Greg"])
(into players new-players)

Hased Maps | Maps

operation	sets	maps
declare	def #{}	def {}
add to	conj	assoc
remove	disj	dissoc
lookup	contains?	get, contains?
sub		keys, vals
merging	into	merge
sorted		sorted-map

• Look up with a default, assign default values if not found
• great for representing Domain Objects
• Use Records for polymorphic behaviour, OO styled interfaces protocols

statements vs expressions

expressions return values, whereas statements do not

Programming Styles

• Use do blocks with if only if your bodies have side effects! (Why?)

Branching / Conditional Flow

using

1. if and if do
2. when
3. cond and else

Whats the difference b/w if and when?

if - handle both trythy and falsey Branching. Side-effects in do block when - only when truthy cndition has to be handleded

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