DSH Calculator

A deterministic math tool for DSH agents: it gives the model a real evaluation engine instead of mental arithmetic, so 0.1 + 0.2 answers 0.3 and money math does not drift.

The engine is a hand-written tokenizer plus a recursive-descent parser — no eval, no Function — in one dependency-free file, core.js.

What it does

• Operators: + - * / ^ (or **) % !, parentheses, unary minus, scientific notation 1.5e-3, and the × ÷ − × aliases.
• Constants: pi e tau phi inf.
• Functions: sqrt cbrt abs sign ceil floor round trunc exp expm1 ln log(x) log(x,base) log2 log10 sin cos tan asin acos atan atan2 sinh cosh tanh pow mod gcd lcm min max hypot radians degrees.
• Variables: pass variables: {"r": 3.5} and reference r in the expression.
• Batches: pass an array as expression, up to 50 expressions per call.
• Actionable errors: syntax, domain and division-by-zero failures come back with a position, so the model can correct itself instead of guessing.
• Two precisions:
  • float (default) — IEEE doubles, output rounded to 15 significant digits.
  • exact — arbitrary-precision decimal (BigInt backed) for money math. Supports + - * / %, integer ^ and !; functions and irrational constants are rejected explicitly rather than silently rounded.

Install

From the plugin market (search for "DSH Calculator"), or by hand:

dsh plugin --profile web add https://github.com/QqiqiQ/dsh-calculator/releases/latest/download/dsh-calculator.tgz

Then restart dsh web. The bundle registers a single calculate tool for every session of the profile, and appends a short usage rule to the system prompt so the model reaches for the tool instead of estimating.

Usage

// single expression
{ "expression": "sqrt(2)^2" }                              // → 2
// variables
{ "expression": "2 * pi * r", "variables": { "r": 3 } }    // → 18.8495559215388
// batch
{ "expression": ["0.1 + 0.2", "10!", "log(8, 2)"] }        // → 0.3 / 3628800 / 3
// exact decimal mode
{ "expression": "price * qty",
  "variables": { "price": "19.99", "qty": 3 },
  "precision": "exact" }                                   // → 59.97

OpenCode (optional)

The same engine also runs as an OpenCode custom tool — opencode/tools/calculate.ts; the tool name comes from the filename. Copy it together with a copy of core.js named calculator.core.js into .opencode/tools/ (project) or ~/.config/opencode/tools/ (global):

$dst = "<your project>\.opencode\tools"
New-Item -ItemType Directory -Force $dst
Copy-Item .\opencode\tools\calculate.ts $dst
Copy-Item .\core.js "$dst\calculator.core.js"

Re-copy calculator.core.js after upgrading the engine, so both sides stay on the same implementation.

Development

node test.js   # 44 assertions, no dependencies

License

MIT