Advanced Features

Do-Notation

Chained operations on tensors:

do [1, 2, 3]
  ↦ λ→ ₀ × 2
  ▸ λ→ ₀ > 3
end
# Result: [4, 6]

With let bindings:

do [1, 2, 3, 4, 5]
  let x ← ₀ × 2
  ↦ λ→ ₀ + 1
end

Inline operators:

do [10, 20, 30]
  + 5
  × 2
end
# Result: [30, 50, 70]

Cast Expressions

Form Syntax Returns
Static expr as Type Type
Force expr as! Type Type
Try expr as? Type Option<Type> 
5 as! F                      # Force cast to Float
x as? String                 # Try cast, returns Option

Modules

Each .goth file is a module. Import with use:

use "prelude.goth"
use "../stdlib/option.goth"

The use declaration takes a relative path and inlines all declarations into the current namespace.

Standard Library Modules

Module Description
prelude.goth Core combinators (id, const, flip, compose)
list.goth List/array operations
math.goth Math functions with uncertainty propagation
option.goth Generic Option (some, none, mapOpt, flatMapOpt)
result.goth Generic Result (ok, err, mapRes, flatMapRes)
string.goth String manipulation
tui.goth Terminal UI (ANSI escapes, cursor, raw mode)
crypto.goth SHA-256, SHA-1, MD5, HMAC, PBKDF2
random.goth Seeded PRNG (xorshift64) with state-passing
json.goth JSON parser and serializer (detail)

JSON

The json.goth module provides a pure-Goth JSON parser and serializer. JSON values are represented as tagged 2-tuples ⟨tag, payload⟩:

Tag Type Payload Constructor
0 null 0 jsonNull ⟨⟩
1 bool Bool jsonBool ⊤
2 number F64 jsonNum 3.14
3 string String jsonStr "hi"
4 array [n]Json jsonArr [...]
5 object [n]⟨String, Json⟩ jsonObj [⟨"k", v⟩]

Parse and extract fields:

use "stdlib/json.goth"

╭─ main : () → String
╰─ let r = parseJson "{\"name\":\"Goth\",\"version\":1}"
   in if ¬(r.0) then "error: " ⧺ r.2
   else let json = r.1
   in let name = jsonGet "name" json
   in if name.0 then asStr name.1 else "unknown"

Build and serialize:

let obj = jsonObj [⟨"x", jsonNum 1.0⟩, ⟨"y", jsonArr [jsonBool ⊤, jsonNull ⟨⟩]⟩]
in toJson obj
# {"x":1,"y":[true,null]}

Core API:

Function Signature Description
parseJson String → ⟨Bool, Json, String⟩ Parse; ⟨⊤, val, ""⟩ or ⟨⊥, 0, msg⟩
toJson Json → String Serialize to compact JSON
jsonGet String → Json → ⟨Bool, Json⟩ Lookup key in object
jsonIndex ℤ → Json → ⟨Bool, Json⟩ Index into array
jsonKeys Json → [n]String Object keys
jsonValues Json → [n]Json Object values
jsonLen Json → ℤ Array/object length
jsonType Json → String "null", "bool", "number", etc.

See the full JSON reference for all constructors, predicates, and extractors.

Random Number Generation

The random.goth module returns ⟨value, nextSeed⟩ tuples for explicit state threading:

use "stdlib/random.goth"

╭─ main : ℤ → [n]F64
╰─ let seed = entropy ⟨⟩
   in let ⟨vals, _⟩ = randFloats ₁ seed
   in vals
Function Signature
entropy () → I64
randFloat I64 → ⟨F64, I64⟩
randFloatRange F64 → F64 → I64 → ⟨F64, I64⟩
randInt I64 → I64 → I64 → ⟨I64, I64⟩
randBool F64 → I64 → ⟨Bool, I64⟩
randNormal I64 → ⟨F64, I64⟩
randGaussian F64 → F64 → I64 → ⟨F64, I64⟩
randFloats I64 → I64 → ⟨[n]F64, I64⟩
randInts I64 → I64 → I64 → I64 → ⟨[n]I64, I64⟩
randNormals I64 → I64 → ⟨[n]F64, I64⟩

REPL

Start the REPL with goth (no arguments).

Command Short Action
:help :h, :? Show commands
:type expr :t Infer type
:ast expr   Show parse tree
:load file :l Load and execute file
:clear :c Clear environment
:quit :q Exit

Multi-line input continues automatically when delimiters are unbalanced or the line ends with an operator.

CLI

goth                         # Start REPL
goth program.goth            # Run file
goth program.goth 5 10       # Run with arguments
goth -e 'Σ [1, 2, 3]'       # Evaluate expression
goth -c program.goth         # Type check only
goth --to-json program.goth  # Emit JSON AST
goth --from-json ast.json    # Run from JSON AST