CLI: repl

The REPL (Read-Eval-Print Loop) lets you interactively explore ISL syntax, evaluate expressions, and test specification fragments.

Usage

shipgate repl [options]

Options

Flag	Description
--load <file>	Load an ISL file on start
--context <json>	Set initial evaluation context
--parse	Parse mode (non-interactive, for piped input)

Starting the REPL

$ shipgate repl

ISL REPL v1.0.0
Type expressions, definitions, or :help for commands.
isl>

REPL commands

Command	Description
:help	Show available commands
:load file	Load an ISL file
:clear	Clear the current context
:ast	Show AST for last expression
:type expr	Show type of an expression
:exit	Exit the REPL

Examples

Evaluate expressions

isl> 2 + 3
5

isl> "hello".length
5

isl> true and false
false

isl> 10 > 5 implies 3 < 7
true

Define types and entities

isl> type Money = Decimal { min: 0, precision: 2 }
Type Money defined

isl> entity User { id: UUID, name: String, email: Email }
Entity User defined

isl> enum Status { ACTIVE, INACTIVE }
Enum Status defined

Test expressions with context

isl> :context {"balance": 100, "amount": 50}

isl> balance >= amount
true

isl> balance - amount
50

isl> balance - amount >= 0
true

Load a spec file

isl> :load user-service.isl
Loaded: domain UserService (1 entity, 2 behaviors)

isl> :type User.email
Email

isl> User.count
0

Piped input

Use --parse mode for non-interactive use:

echo 'type Money = Decimal { min: 0, precision: 2 }' | shipgate repl --parse

Use cases

Exploring ISL syntax

Use the REPL to learn ISL before writing full specs:

isl> all(x in [1,2,3]: x > 0)
true

isl> count(x in [1,2,3,4,5]: x > 3)
2

isl> sum(x in [10, 20, 30]: x)
60

Testing preconditions

Set up context and test your preconditions interactively:

isl> :context {"email": "user@example.com", "name": "Alice", "amount": 100}

isl> email.is_valid
true

isl> name.length > 0
true

isl> amount > 0
true

isl> amount > 0 and email.is_valid and name.length > 0
true

Checking types

isl> :type 42
Int

isl> :type "hello"
String

isl> :type true and false
Boolean

isl> :type [1, 2, 3]
List<Int>

Exit codes

Code	Meaning
0	Clean exit