Eve System Library

The Standard Library is what every program has without an import: the built-in functions and the standard streams. The System Library is the set of modules that connect a program to the machine around it: the console, the file system, the clock, the shell and the network. A module of the system library is imported with from … use, like any other module, from $EVE_LIB.

Status: only io and exception are drafted for Eve 0.1 (evevm/lib/). The other modules are planned for the data client (level 3) and later; their names and members are a design, waiting for the author's review (plan/decision_level3.md, Q-024).

The modules

Module	What it holds	Status	Page
`io`	standard streams: `write`, `print`, `read`, `error`, `warning`, `log_err`, `log_wrn`	0.1 draft	Standard Library
`exception`	the class `Error`, `raise`, `expect`, `assert`, the error and warning codes	0.1 draft	Exceptions
system variables	`$EVE_LIB`, `$EVE_OUT`, `$HOME` and every environment variable as `$NAME`	0.1	EVE VM
`call` (shell)	run an operating system command, capture its output	0.1 design	Shell Commands
`fs`	files, folders and paths in one module: read and write text and bytes, lines as a stream, list a folder, glob; the operator `/` joins paths	designed, level 5	Files and ETL
`time`	the clock, `Instant`, `DateTime` with a zone, sleeping	designed, level 5	Date and Time
`secret`	`Secret`: tokens and passwords that never appear in logs or in code	designed, level 5	Databases
`os`	`run(command, arguments, cwd: dir)` without a shell, gives the exit code and the output	designed, level 5	Shell Commands
`csv`, `json`, `dat`	read and write files as streams of rows or nodes, typed by a record class, in Unicode; `.gz` files are read on the fly	designed, level 5	Files and ETL
`task`	channels and the worker pool of parallel aspects	planned, level 4	Concurrency
`database`	connections, `Record` and `Table`, tracked records, transactions per job, direct SQL, checkpoints	designed, level 5	Databases
`http`	the client in level 5 (`get!`, `post!`, `request!`); serving in level 6	client designed, level 5	Networking

Rules of the system library

Written in Eve. A module is Eve code. Only the few primitives that need the machine are external declarations, implemented by the virtual machine in Zig (see EVE VM);
Errors are values of the language. A module raises the errors of the exception module, so one recover region handles them all;
Thread safety is declared by the compiler. A function of a module is thread safe only if it keeps no plain shared variable; a concurrent aspect can call it only then (see Thread safety);
Documented from the code. eve --doc builds the reference of a module from its ** comments and signatures.

Example

The io module is always available. The example below reads a name and writes a line; it uses only the functions of the standard streams.


# ask a name and greet
driver greeting is
  process main is
    new name := "";
    read(name, "name: ");
    print "Hello,", name;
  return;
end greeting;

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