Keywords

Strict needs very few keywords. Most code can only be written in one way, so swapping arguments or changing the style usually means the code no longer compiles, or at least doesn't behave the same way. You will understand any .strict code you read. Writing it is harder because of all the strict rules.

Keywords and operator words can't be used as names.

Declarations

Keyword	Meaning	See
has	Member that is set once when the instance is created	Members and Variables
constant	Member or variable computed only from constants, always optimized away	Members and Variables
let	Variable that doesn't change	Members and Variables
mutable	Member or variable that may change (parameters never do)	Members and Variables
with	Constraint on a member or parameter	Types
from	Custom constructor	Types

Control flow

Keyword	Meaning	See
if, else	Conditional blocks, else if chains and selector if	If
then	Single-line conditional condition then a else b and selector cases	If
for	The only loop, also the for method that makes a type iterable	For
as long as	Repeat a for while its condition is true	For
in	Containment (is in), and naming a loop variable	For
return	Leave a method early with a value	Methods

Operators

Keyword	Meaning
is, is not	Equality, also used by every test
is in, is not in	Containment
and, or, xor, not	Logic, as English words instead of C symbols
to	Conversion: 5 to Text, and conversion methods like to Number
+ - * / % ^ < > <= >=	Arithmetic and comparison
=	Assignment. Equality is always is
()	Lists, which includes method parameters and call arguments. An empty () is never written

Implicit names

Name	Meaning
value	The instance in a method, the current element in a for loop, the member value in a with constraint
index	The position in a for loop, starting at 0
outer	The value from outside the current for loop
true, false	The two Boolean values
None	The state of an optional value that was never set, see or None

Base types

The base types in the repository root are always available, everything else is found by name. Base Types describes each of them:

Any, Boolean, Byte, BytesReader, BytesWriter, Character, Closeable, Dictionary, Directory, Enum, Error, ErrorWithValue, File, Generic, HashCode, Iterator, Length, Library, List, Logger, Method, Mutable, Name, Number, Path, Process, ProcessResult, Range, Stacktrace, Text, TextReader, TextWriter, Type, Variable

Decimal precision

Step in a numeric constraint declares decimal precision: has price Number with Step 0.01. Add Floor or Ceiling for directed rounding. It is a constraint form rather than a separate decimal base type. See Decimals.

Package structure

A Strict package is a folder:

• Every type is a .strict file. Subfolders are packages of their own.
• A README.md explains the package and should show how to use it. This is the only place for explanations, because code has no comments.
• .editorconfig sets up any editor for tabs and the Strict style.

See Grammar for the complete syntax.