Euler's totient φ(n) — the count of integers in [1, n] coprime to n — for a positive integer ≤ 10^15 (it is computed from the prime factorization).

Ground-up hotel development underwriting. Land + hard costs (S-curve draw) + soft costs + developer fee, funded by a construction loan (LTC) with capitalized interest, refinanced into a permanent loan sized on min(stabilized-value LTV, DSCR) at the CL term. Occupancy begins the month after construction; the hold is measured from construction end. Returns unlevered and levered project IRR and MOIC. Reconciled to a SHA-pinned Excel model — see /hotel-dev/reconciliation.

Generate an RFC 6238 time-based one-time password from a base32 secret. Uses the current time by default, or an explicit unix timestamp (seconds); configurable period (default 30s), digits (default 6) and algorithm (default SHA1). Also returns the counter and seconds remaining in the window.

Industrial acquisition underwriting — NNN and gross lease multi-tenant. Per-tenant lease modeling with contractual rent bumps and rollover vacancy. Blended OpEx based on NNN vs gross SF mix. Returns cap rate, NOI per SF, WALE, DSCR, IRR and MOIC.

Generate an RFC 4226 counter-based HMAC one-time password from a base32 secret and counter. Configurable digits (6–10, default 6) and algorithm (SHA1/SHA256/SHA512, default SHA1). An invalid base32 secret is a clean 400.

CRC-32 (IEEE 802.3 polynomial, as used by zip, gzip and PNG) over the input payload. Returns the checksum as an unsigned integer and 8-digit hex. Non-cryptographic — for error detection only.

Add, subtract, multiply or divide two fractions and return the exact, fully-reduced result. All computation is done in BigInt so there is no floating-point error. Dividing by a zero fraction is a clean 400.

Generate a random string of a given length from a named charset (alphanumeric, alpha, lower, upper, numeric, hex, base58) or a custom alphabet. Unbiased character selection.

Search the constants table by key, symbol or name substring. Exact matches rank first, then prefix matches, then substring matches. Returns up to `limit` constants (default 20) plus the total match count.

Encode a word with Double Metaphone, returning a primary and a secondary code to capture alternate pronunciations (useful for non-English names).

Encode a word with the classic Soundex algorithm (letter + 3 digits) for phonetic matching of names.

Encode a word with the Metaphone algorithm — more accurate than Soundex for English pronunciation.

Draw a random sample from a provided array — without replacement by default (a fair shuffle), or with replacement when unique is false. count defaults to 1.

Adler-32 checksum (as used by zlib) over the input payload. Faster than CRC-32 but weaker for short inputs. Returns the checksum as an unsigned integer and 8-digit hex. Non-cryptographic.

Transcribe text to Unicode braille (grade-1 / uncontracted English braille), with capital and number signs. Characters with no grade-1 representation are clean 400s.

Split YAML front-matter from a document — returns the parsed metadata object and the remaining content body. Malformed YAML is rejected as a clean 400.

Render a barcode (Code128, Code39, EAN-13/8, UPC-A/E, ITF-14, DataMatrix, PDF417) as SVG or PNG data URL.

Decode HTML entities (named, decimal and hex numeric references) back into plain text.

Fletcher checksum over the input payload, in 16-bit (default) or 32-bit width. Returns the checksum as an unsigned integer and hex. Non-cryptographic.

Given an emoji character (or any string), return its code points and — if known — its name, category, shortcodes and tags. An unknown emoji is a successful result with `known:false`, not an error.