raskell

raskell

Functional and Concatenative Stream Programming in Ruby

Usage:

Reminder: Lambdas can be applied with [*args] notation and .() is syntactic sugar for .call() f = ->(x) { x + 2 } f[1] , f.(1), and f.call(1) all evaluate as 3

Lambdas can be partially applied, yielding a new lambda, with call plus = ->(x,y) { x + y } plus10 = plus.(10) ## or plus[10] plus10.(20) evaluates as 30

Lambda Composition with * (right-associative) ( (f * g * h).(x) == f.(g.(h.(x)))) times10 = ->(x) { x * 10 } minus3 = ->(x) { x - 3 } double = ->(x) { x * 2 }

(times10 * minus3 * double).(5) evaluates as 70 (double * minus3 * times10).(5) evaluates as 94

Lambda Pipelining with | (left-associative) (f | g | h).(x) == h.(g.(f.(x))) (times10 | minus3 | double).(5) evaluates as 94 (double | minus3 | times10).(5) evaluates as 70

Lambda Tupling with + (associative) (times10 + minus3 + double).(5) evaluates as [50, 2, 10]

Objects, when called, act like constant functions that throw away any values applied to them 5.(1,2,3,[4,7]) evaluates to 5

Arrays, when called, map across themselves calling each element with the arguments it was called with [times10, minus3, double].(5) evaluates to [50, -15, 10] [plus, times10, 3].(0,1) evaluates to [1, 0, 3] Note that [plus,times10,3][0,1] evaluates to [plus], not [1, 0, 3], so be careful where you use func[] as shorthand func.() or func.call()!

Streams, when called, map across themselves calling each element with the arguments it was called with [times10, minus3, double].to_stream.(5).to_a evaluates to [50, -15, 10] [plus, times10, 3].to_stream.(0,1) evaluates to [1, 0, 3].to_stream Note that [plus,times10,3].to_stream[0,1] evaluates to [plus].to_stream, not [1, 0, 3].to_stream, so be careful where you use func[] as shorthand func.() or func.call()!

Preface any collection function with F. to call that particular function F.map.(times10 * plus10).([1,2,3]) evaluates as [100, 200, 300]

Available Operators to Overload in Ruby

(unary) !, ~, +, -

(binary) **, *, /, %, +, -, <<, >>, &, |, ^, ||, && =, +=, *=, -=, <, <=, >=, >, ==, ===, !=, =, !, <=> [],[]=

Using in Raskell so far [], *, **, ^, |, &, +, %, <<, >>

=~ and !~ will be good for later when I have 'regular expressions' over arbitrary asterated semirings - then i can match if the data, path, whatever matches a regex of allowable types - this gives us a powerful form of type constraint for free