A short tour of the standard library. Each module's full reference is its own page under @link["modules/index.html"]{Modules}.
@subsection{std/prelude}
The prelude is what every module has without importing anything: the collections and their functions, strings and characters, files and ports, Concurrent ML and scopes, and the macros the language is written with, such as @code{cond}, @code{if-let} and @code{type/derive}. Its reference also covers the builtins, the functions compiled into the runtime rather than written in Bjolang, since every program gets them with the prelude. At the REPL, @code{:show name} prints the same documentation.
For more details, see @link["modules/std/prelude.html"]{@code{(std prelude)}}.
Numbers beyond the operators. Integer division has Racket's names: @code{quotient} and @code{remainder} are what @code{/} and @code{%} do, and @code{modulo} takes the sign of the divisor, so @code{(modulo -1 10)} is 9. There are @code{gcd}, @code{lcm}, an integer @code{expt} and an exact @code{integer-sqrt} at every integer type, the @code{exact-} roundings from a double to an int, and the rest of @code{System.Math} over doubles. The prelude has @code{abs}, @code{min}, @code{max} and @code{clamp} from here without an import.
For more details, see @link["modules/std/maths.html"]{@code{(std maths)}}.
Formatting in Bjolang is divided into two layers: interpolation and layout.
Interpolation provides a simple way to combine mixed scalar types into strings or print them directly using @code{println*} and @code{str*}.
The layout layer provides a composable block algebra for more complex text formatting, such as padding, aligning, wrapping paragraphs, and laying out tables.
Bjolang provides a built-in regular expression engine. Unlike languages that use strings for regex (like @code{"[a-z]+"}), Bjolang uses structural S-expressions. This means you never have to double-escape characters, and the compiler validates your patterns at compile time. Built-in character sets and anchors are written as keywords (e.g., @code{:bos}, @code{:digit}), and operations that group or repeat patterns are function-like lists (e.g., @code{(seq ...)}).
The @code{std/http} module allows you to build and send HTTP requests. Sending a request three ways — blocking, suspending, or as an event — is the only thing that differs between the entry points. There is no C# in this module: @code{System.Net.Http} is reached with @code{import/extern}, and the response body is an ordinary @code{TextInputPort}.
The @code{std/run} module provides a way to run external programs. A form is one thing to run, written as a quoted literal, like @code{'(cat "hej.txt")}. You can connect programs in a pipe with @code{'(pipe (cat "a") (wc -l))}, and redirect input and output to files. Redirections can nest, and you can even splice computed arguments or write stages in Bjolang.
The random module provides a ChaCha20 generator, seeded with 256 bits from the OS CSPRNG, with one generator per thread. The default path locks nothing and shares nothing, making it safe and fast on a bjoroutine. The ambient source has no state to race on, so drawing from multiple threads is efficient. You can generate random integers and more.
This module provides types and functions for handling time. The clock is an argument (with a default that a program can rebind), and the types refuse operations that mean nothing, such as adding a calendar day to an instant. The module separates @code{Date} (a calendar date without a timezone), @code{Time} (a time of day without a timezone), and @code{DateTime} (a date and time without a timezone), as well as handling timezones.
bjodat is Bjolang's shapes read as data: no evaluation, no macro expansion, no environment. It is what a package manifest, a lockfile, or a config file is written in. You can parse text straight into a record using @code{bjodat-parse-<Name>}, which avoids intermediate trees and allocations.
The @code{text/json} module provides JSON parsing and generation capabilities. Like @code{bjodat}, it allows for working with structured data but using the standard JSON format, which is essential for web communication.
For more details, see @code{prelude.org} and related standard library documentation.
