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Verified Scarp alpha.2: module constants and source inspection

Compiler: v0.0.5-alpha.2, published November 2, 2026. This tutorial reproduces three complete tagged examples and their exact expected stdout. Imported source files are reproduced before the entry script, so the TypeScript evidence checker can detect missing or reordered dependencies. Each fixture is checked and executed in the separate alpha.2 CI job.

This tutorial is specific to the published alpha.2 release, not the main alpha.1 reference. The compiler is an interpreter; module inspection does not produce an executable.

1. Compile-time scalar constants across three files

Create these files with the exact paths shown. Paths in an import are resolved relative to the importing file.

modules/constant_base.srp — public literal constants:

pub bind base = 10;
pub bind multiplier = 4;
pub bind label = "constant expressions";

modules/constants.srp — compile-time expressions and a pure function:

import "constant_base.srp" as settings;
bind step = 2;
pub bind answer = settings.base * settings.multiplier + step;
pub bind label = settings.label;
pub bind ready = answer == 42 and not false;
pub bind ratio = (1.5 * 2.0) / 4.0;

pub pure funcra adjust(value: integer = answer) -> integer
needs ready;
ensures result >= answer;
{
    return value;
}

constant_expressions.srp — entry program:

import "modules/constants.srp" as constants;
pub bind doubled = constants.answer * 2;
print(constants.label, constants.answer, doubled, constants.ready, constants.ratio, constants.adjust());

Expected stdout from the published output file:

constant expressions 42 84 true 0.75 42

settings.base * settings.multiplier + step is evaluated while compiling the module, not through a runtime global initialization system. pub bind doubled is another module constant. The imported pure function can read published constants and use its default argument. Constant initializers remain deliberately restricted: arbitrary runtime function calls, indexing, collections and side effects are not allowed in the initializer expression. See the compiler's tagged constant expression reference.

2. Inspect a module without running its entry statements

modules/inspection.srp — notice public and private declarations:

pub bind label = "module tools";
bind offset = 1;

pub pure funcra adjusted(value: integer, step: integer = 2) -> integer
    needs step >= 0;
    ensures result >= value;
{
    return helper(value) + step;
}

pure funcra helper(value: integer) -> integer {
    return value + offset;
}

module_inspection.srp — import and call:

import "modules/inspection.srp" as tools;
print(tools.label, tools.adjusted(39));

Expected stdout when running the program:

module tools 42

The distinct scarp modules module_inspection.srp command does not run the print. It reports source/module metadata, including import relationships, public/private declarations, parameters and function signatures. A private symbol can be visible in the inventory without being importable from another module. Use scarp run module_inspection.srp to produce the stdout above.

3. Versioned JSON module metadata

inspection_json.srp — a self-contained source module with two compile-time constants and one function:

pub bind base: integer = 6;
pub bind answer: integer = base * 7;
pure funcra echo(value: integer = answer) -> integer {
    return value;
}
print(echo());

Expected stdout on scarp run:

42

This published JSON inspection snapshot records the source-local metadata (not the runtime output):

{"schema_version":1,"entry":0,"modules":[{"id":0,"path":"inspection_json.srp","imports":[],"dependencies":[],"dependents":[],"symbols":[{"name":"base","public":true,"span":[9,13],"kind":"constant","type":"integer"},{"name":"answer","public":true,"span":[37,43],"kind":"constant","type":"integer"},{"name":"echo","public":false,"span":[77,81],"kind":"function","pure":true,"result":"integer","parameters":[{"name":"value","type":"integer","has_default":true,"span":[82,87]}]}]}],"constant_dependencies":[{"source":0,"declaration":[37,43],"target":0,"target_declaration":[9,13],"span":[55,59]}]}

schema_version: 1 is the format identifier. span values are half-open UTF-8 byte offsets, not line numbers or Unicode-character offsets. The constant_dependencies record connects answer to base. A native filesystem CLI inspection may serialize a different module path label from the in-memory snapshot, because its source loader uses the actual path. Do not treat these path labels as cross-machine identifiers. The new test compares stable metadata and typed spans to the published snapshot while allowing the path label to vary.

Run the examples with the matching compiler

Use the alpha.2 executable and preserve all modules/ files in the same relative directory as the entry programs:

scarp check constant_expressions.srp
scarp run constant_expressions.srp
scarp modules module_inspection.srp
scarp modules --json inspection_json.srp
scarp run inspection_json.srp

A successful check is silent. run produces the expected stdout above; modules provides static information and --json selects its machine-readable form. Neither is a native compiler or a package manager.

Evidence: tagged Scarp examples, module inspection reference and verification approach.

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