Source Files and Execution

Language design. Generated coverage names measured programs and target restrictions; examples here illustrate the design.

Current command line

Use dewy file.dewy to run, dewy check file.dewy to check without output, or dewy build file.dewy --release -o program to save a native executable. In a checkout use ./tools/dewy in place of dewy. build --target wasm32 emits a browser page. See installation and target-scoped coverage.

Source-language rules

A source file is a compilation unit. Its executable top-level expressions run once in source order after imported dependencies have initialized.

A program does not require main. When a zero-argument function named main exists in the entry module, the program invokes it after top-level initialization.

printl"initializing"

let main = ():>void => {
    printl"running"
}

main returns void or the errors that reach it: void | E, an ordinary result type, declared or inferred. It gives no exit code: success exits 0, and a script that needs a particular code calls exit(n). An error reaching main is printed on standard error and ends the program with its kind's code, assigned 1, 2, 3, … in the order the kinds are declared (a declared result fixes the order), below 126; an error type may pin its own with an exit_code member. dewy build --exit-codes prints the table. Additional standardized entry parameters such as command-line arguments and environment access are provisional.

An explicit top-level call to main() is an ordinary call and does not suppress automatic entry invocation.

Imported modules initialize once in dependency order. Import cycles and colliding names are errors unless a future construct explicitly defines a valid cycle or disambiguation.