Changelog for egison-5.0.0

Changelog

Static Type System: Introduced a static type system for Egison.
- Type annotations for function parameters and return types: def f (x: Integer) : Integer := x + 1
- Polymorphic type parameters: def id {a} (x: a) : a := x
- Type inference with unification
Type Classes: Added Haskell-style type class system.
- Type class declarations: class Eq a where ...
- Instance declarations: instance Eq Integer where ...
- Superclass constraints with extends: class Ord a extends Eq a where ...
- Type class constraints in function signatures: def f {Eq a} (x: a) (y: a) : Bool := x == y
Inductive Data Types: Added support for user-defined algebraic data types.
- Data type declarations: inductive Maybe a := | Nothing | Just a
- Pattern inductive types: inductive pattern [a] := | [] | (::) a [a]
Symbol Declarations: Added declare symbol for declaring symbolic variables used in tensor calculations.
- declare symbol x, y, z : Integer
Pattern Function Declarations: Added typed pattern function syntax.
- def pattern twin {a} (p1 : a) (p2 : MyList a) : MyList a := ...
New Built-in Types: MathExpr, IO, DiffForm

> let mod x y := x % y in 103 `mod` 10
3

> `(a + b) + `(a + b) -- QuoteExpr, which prevents (a + b) from unpacking
2 * '(a + b)
> 'exp x              -- QuoteSymbolExpr
exp x

Changed the specification of generateTensor so that the generation function takes indices as a collection. (#267)

Enabled user-defined infixes for expressions and patterns: https://egison.readthedocs.io/en/latest/reference/basic-syntax.html#infix-declaration
Allowed let expression to decompose data. Unlike match expressions (of Egison), this does not require matchers and the decomposition pattern is limited.

> let (x :: _) := [1, 2, 3] in x
1
> let (x :: _) := [] in x
Primitive data pattern match failed
  stack trace: <stdin>

> (\(x, _) -> x) (1, 2)
1

> let add x y := x + y in map (add 1) [1, 2, 3]
[2, 3, 4]

Huge speedup in mathematical programs:
- Reimplemented math normalization, which was originally implemented in Egison, to the interpreter in Haskell.
- Implemented lazy evaluation on tensor elements.
Added new syntax for symmetric / anti-symmetric tensors.

def x := 1

io was previously defined as a syntastic constructs, but it is changed into a primitive function. Namely, users will need to wrap the arguments to io in a parenthesis, or insert $ after io.

-- Invalid
io isEof ()

-- OK
io (isEOF ())
io $ isEOF ()

Added a command line option --no-normalize to turn off math normalization implemented in the standard math library.
Revived TSV input options: https://egison.readthedocs.io/en/latest/reference/command-line-options.html#reading-tsv-input
Deprecated redefine.