schala/TODO.md

#Typechecking Notes

(cf. cardelli paper)

Given a length function def:

fn length(x) {
 if x.is_null {
   0
  } else {
   succ(length(x.tail))
  }
}

Constraints: .null: List a -> bool .tail: List a -> List a 0: Nat succ: Nat -> Nat

TODO Items

-make the REPL more advanced!

-Plan of attack: -write a visitor pattern for AST -convert AST type to including SourceMap'd wrappers (w/ .into()) -at the same time, amke sure the visitor pattern "skips over" the SourceMap'd stuff so it can just care about AST structure

• AST : maybe replace the Expression type with "Ascription(TypeName, Box) nodes??
• parser: add a "debug" field to the Parser struct for all debug-related things

-scala-style html"dfasfsadf${}" string interpolations!

-fuzz test schala

-look into Inkwell for LLVM

*A neat idea for pattern matching optimization would be if you could match on one of several things in a list ex: if x { is (comp, LHSPat, RHSPat) if comp in ["==, "<"] -> ... }

• https://nshipster.com/never/ -https://cranelift.readthedocs.io/en/latest/?badge=latest

-consult http://gluon-lang.org/book/embedding-api.html

• if/match playground

simple if if x == 1.0 { "a" } else { "b" }

one comparison multiple targets: if x == { 1.0 -> "a", 2.0 -> "b", else -> "c" }

different comparison operators/ method calls: if x { == 1.0 -> "a", eq NaN -> "n", .hella() -> "h", else -> "z" }

pattern matching/introducing bindings: if alice { .age < 18 -> "18", is Person("Alice", age) -> "${age}", else -> "none" }

pattern matching w/ if-let: if person is Person("Alice", age) { "${age}" } else { "nope" }

-https://soc.github.io/languages/unified-condition-syntax syntax:

if <cond-expr>" then <then-expr> else <else-expr> if <half-expr> \n <rest-expr1> then <result1-expr> \n <rest-expr2> then <result-expr2> else <result3-expr> -and rest-exprs (or "targets") can have 'is' for pattern-matching, actually so can a full cond-expr

UNIFIED IF EXPRESSIONS FINAL WORK:

basic syntax:

if_expr := if discriminator '{' (guard_expr)* '}' guard_expr := pattern 'then' block_or_expr' pattern := rhs | is_pattern is_pattern := 'is' ??? rhs := expression | ???

if the only two guard patterns are true and false, then the abbreviated syntax: 'if' discriminator 'then' block_or_expr 'else' block_or_expr can replace 'if' discriminator '{' 'true' 'then' block_or_expr; 'false' 'then' block_or_expr '}'

• Next priorities: - get ADTs working, get matches working

• inclusive/exclusive range syntax like .. vs ..=

• sketch of an idea for the REPL: -each compiler pass should be a (procedural?) macro like compiler_pass!("parse", dataproducts: ["ast", "parse_tree"], { match parsing::parse(INPUT) { Ok( PASS.add_artifact( }

-should have an Idris-like cast To From function

• REPL:
  • want to be able to do things like :doc Identifier, and have the language load up these definitions to the REPL

• change 'trait' to 'interface' -think about idris-related ideas of multiple implementations of a type for an interface (+ vs * impl for monoids, for preorder/inorder/postorder for Foldable)

• Share state between programming languages

• idea for Schala - scoped types - be able to define a quick enum type scoped to a function ro something, that only is meant to be used as a quick bespoke interface between two other things

• another idea, allow: type enum { type enum MySubVariant { SubVariant1, SubVariant2, etc. } Variant1(MySubVariant), Variant2(...), }

• idea for Schala: both currying and default arguments! ex. fn a(b: Int, c:Int, d:Int = 1) -> Int a(1,2) : Int a(1,2,d=2): Int a(,1,3) : Int -> Int a(1,2, c=): Int -> Int a(,,_) : Int -> Int -> Int -> Int

*Compiler passes architecture

-ProgrammingLanguageInterface defines a evaluate_in_repl() and evaluate_no_repl() functions -these take in a vec of CompilerPasses

struct CompilerPass { name: String, run: fn(PrevPass) -> NextPass }

-change "Type...." names in parser.rs to "Anno..." for non-collision with names in typechecking.rs

-get rid of code pertaining to compilation specifically, have a more generation notion of "execution type"