Expanded is and isnt operators #866

somebee · 2023-08-17T08:22:38Z

somebee
Aug 17, 2023
Maintainer

Imba will land a very neat feature in the next release. The existing is and isnt operators are expanded to make complex pattern matching more elegant:

let num = 1
let str = 'done'

# Basic usage is essentially like `===` and `!==` - no change there.
num is 1
num isnt 2
str is 'done'
str isnt 'ready'

# The right side of `is` can be a parenthesis with nested matchers.
num is (1 or 2)
str isnt 'ready'
str is 'done'
str is ('ready' or 'done')

# Now to the more powerful things. If the right-side implements a `#matcher` method, Imba
# will call this to see if the left-side matches. So lets create a pattern:

# Implements a matcher that checks if number is odd
const Odd = { #matcher: do(v) v % 2 == 1 }

# Implements a matcher that checks if number is rounded
const Rounded = { #matcher: do(v) v % 1 == 0 }

# Implements a matcher that checks if number is more than 1000
const Huge = { #matcher: do(v) v > 1000 }

# We can now test anything against this using `is` and `isnt` operators.

1 is Odd # Odd.#matcher(1) returns true
2 isnt Odd # Odd.#matcher(2) returns false
	
# This can also be used nested with other conditions
num is (Odd or 2)
2000 is Huge
3 
FF8
is (Huge or (Rounded and Odd))
3.5 isnt (Huge or Rounded)

# Let's create a rich status type:
class Status
	name
	desc

	def #matcher v
		v and v.status == name ? self : false

const Ready = new Status(name: 'ready', desc: "Item is ready for upload")
const Done = new Status(name: 'done', desc: "Upload has completed")

let obj = {
	name: "Hello"
	status: "ready"
}
obj is Ready
obj isnt Done
obj is (Ready or Done)

# Since the Status matcher returns the status itself on match
let status = obj is (Done or Ready)
status === Ready

madmaniak · 2023-08-20T17:24:19Z

madmaniak
Aug 20, 2023
Collaborator

For an easy case like Odd, Rounded, Huge could it be just a function instead of { #matcher: function } object?

0 replies

svallory · 2023-08-20T23:02:12Z

svallory
Aug 20, 2023

This is a really nice base for constructing an assertion library! It would read almost like a document

0 replies

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Expanded is and isnt operators #866

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Expanded is and isnt operators #866

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somebee Aug 17, 2023 Maintainer

Replies: 2 comments

Uh oh!

madmaniak Aug 20, 2023 Collaborator

Uh oh!

svallory Aug 20, 2023

somebee
Aug 17, 2023
Maintainer

madmaniak
Aug 20, 2023
Collaborator

svallory
Aug 20, 2023