args — command-line arguments

Source

lib/args.low

Layer

L2 — host (wrapper over a builtin op)

Capabilities

cap args

Reads the command-line arguments the program received. Arguments are not a value visible everywhere; they are a capability handed to main, which is why the first input is cap args (chapter 16). The module is one wrapper that passes the builtin op arg through.

use args .

proc first_len input a cap args . output usize . effects none . do
  let who option slice u8 args.get a. 0 . .
  guard is_some who. . else return 0 . .
  return len some_value who. . . .
end .

op	shape	notes
arg	(cap args, i u64) → option slice u8	The i-th argument, from 0. none when there is no argument at that position

Table 50.1 — The ops of args

The number of arguments comes from the core op len a. . (the same word as the length of a slice).

Not built: option parsing (--name value), reading an argument as a number.