From afef2e25ff1e81fd9c5dcc513eb52959a1e8da12 Mon Sep 17 00:00:00 2001
From: mat <git@matdoes.dev>
Date: Sat, 13 Apr 2024 00:52:28 -0500
Subject: [PATCH] add numbat as calculator engine

---
 Cargo.lock                              | 467 +++++++++++++++++++++++-
 Cargo.toml                              |   1 +
 README                                  |   2 +-
 default-config.toml                     |   4 +
 src/engines/answer.rs                   |   3 +-
 src/engines/answer/{calc.rs => fend.rs} |   0
 src/engines/answer/numbat.rs            | 196 ++++++++++
 src/engines/mod.rs                      |   9 +-
 src/web/assets/style.css                |   4 +
 9 files changed, 676 insertions(+), 10 deletions(-)
 rename src/engines/answer/{calc.rs => fend.rs} (100%)
 create mode 100644 src/engines/answer/numbat.rs

diff --git a/Cargo.lock b/Cargo.lock
index 4b1fada..3138434 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -82,6 +82,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "arrayvec"
+version = "0.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "96d30a06541fbafbc7f82ed10c06164cfbd2c401138f6addd8404629c4b16711"
+
 [[package]]
 name = "async-compression"
 version = "0.4.6"
@@ -129,6 +135,19 @@ dependencies = [
  "syn 2.0.52",
 ]
 
+[[package]]
+name = "attohttpc"
+version = "0.27.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "184f5e6cce583a9db6b6f8d772a42cfce5b78e7c3ef26118cec3ce4c8c14969b"
+dependencies = [
+ "http 1.0.0",
+ "log",
+ "rustls 0.22.3",
+ "url",
+ "webpki-roots 0.26.1",
+]
+
 [[package]]
 name = "autocfg"
 version = "1.1.0"
@@ -227,6 +246,15 @@ version = "2.4.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ed570934406eb16438a4e976b1b4500774099c13b8cb96eec99f620f05090ddf"
 
+[[package]]
+name = "block-buffer"
+version = "0.10.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3078c7629b62d3f0439517fa394996acacc5cbc91c5a20d8c658e77abd503a71"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "brotli"
 version = "3.4.0"
@@ -316,6 +344,16 @@ dependencies = [
  "uncased",
 ]
 
+[[package]]
+name = "codespan-reporting"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3538270d33cc669650c4b093848450d380def10c331d38c768e34cac80576e6e"
+dependencies = [
+ "termcolor",
+ "unicode-width",
+]
+
 [[package]]
 name = "core-foundation"
 version = "0.9.4"
@@ -332,6 +370,15 @@ version = "0.8.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "06ea2b9bc92be3c2baa9334a323ebca2d6f074ff852cd1d7b11064035cd3868f"
 
+[[package]]
+name = "cpufeatures"
+version = "0.2.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53fe5e26ff1b7aef8bca9c6080520cfb8d9333c7568e1829cef191a9723e5504"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "crc32fast"
 version = "1.4.0"
@@ -341,6 +388,16 @@ dependencies = [
  "cfg-if",
 ]
 
+[[package]]
+name = "crypto-common"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1bfb12502f3fc46cca1bb51ac28df9d618d813cdc3d2f25b9fe775a34af26bb3"
+dependencies = [
+ "generic-array",
+ "typenum",
+]
+
 [[package]]
 name = "cssparser"
 version = "0.31.2"
@@ -375,6 +432,37 @@ dependencies = [
  "syn 1.0.109",
 ]
 
+[[package]]
+name = "digest"
+version = "0.10.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9ed9a281f7bc9b7576e61468ba615a66a5c8cfdff42420a70aa82701a3b1e292"
+dependencies = [
+ "block-buffer",
+ "crypto-common",
+]
+
+[[package]]
+name = "dirs"
+version = "5.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "44c45a9d03d6676652bcb5e724c7e988de1acad23a711b5217ab9cbecbec2225"
+dependencies = [
+ "dirs-sys",
+]
+
+[[package]]
+name = "dirs-sys"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "520f05a5cbd335fae5a99ff7a6ab8627577660ee5cfd6a94a6a929b52ff0321c"
+dependencies = [
+ "libc",
+ "option-ext",
+ "redox_users",
+ "windows-sys 0.48.0",
+]
+
 [[package]]
 name = "dtoa"
 version = "1.0.9"
@@ -396,6 +484,12 @@ version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3a68a4904193147e0a8dec3314640e6db742afd5f6e634f428a6af230d9b3591"
 
+[[package]]
+name = "either"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a47c1c47d2f5964e29c61246e81db715514cd532db6b5116a25ea3c03d6780a2"
+
 [[package]]
 name = "encoding_rs"
 version = "0.8.33"
@@ -560,6 +654,16 @@ dependencies = [
  "byteorder",
 ]
 
+[[package]]
+name = "generic-array"
+version = "0.14.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85649ca51fd72272d7821adaf274ad91c288277713d9c18820d8499a7ff69e9a"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
 [[package]]
 name = "getopts"
 version = "0.2.21"
@@ -630,6 +734,15 @@ version = "0.14.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "290f1a1d9242c78d09ce40a5e87e7554ee637af1351968159f4952f028f75604"
 
+[[package]]
+name = "heck"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "95505c38b4572b2d910cecb0281560f54b440a19336cbbcb27bf6ce6adc6f5a8"
+dependencies = [
+ "unicode-segmentation",
+]
+
 [[package]]
 name = "html-escape"
 version = "0.2.13"
@@ -774,7 +887,7 @@ dependencies = [
  "futures-util",
  "http 0.2.12",
  "hyper 0.14.28",
- "rustls",
+ "rustls 0.21.10",
  "tokio",
  "tokio-rustls",
 ]
@@ -850,6 +963,15 @@ version = "2.9.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f518f335dce6725a761382244631d86cf0ccb2863413590b31338feb467f9c3"
 
+[[package]]
+name = "itertools"
+version = "0.12.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ba291022dbbd398a455acf126c1e341954079855bc60dfdda641363bd6922569"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.10"
@@ -871,6 +993,16 @@ version = "0.2.153"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9c198f91728a82281a64e1f4f9eeb25d82cb32a5de251c6bd1b5154d63a8e7bd"
 
+[[package]]
+name = "libredox"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c0ff37bd590ca25063e35af745c343cb7a0271906fb7b37e4813e8f79f00268d"
+dependencies = [
+ "bitflags 2.4.2",
+ "libc",
+]
+
 [[package]]
 name = "lock_api"
 version = "0.4.11"
@@ -940,6 +1072,7 @@ dependencies = [
  "fend-core",
  "futures",
  "html-escape",
+ "numbat",
  "once_cell",
  "rand",
  "regex",
@@ -986,6 +1119,48 @@ version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e4a24736216ec316047a1fc4252e27dabb04218aa4a3f37c6e7ddbf1f9782b54"
 
+[[package]]
+name = "num-bigint"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "608e7659b5c3d7cba262d894801b9ec9d00de989e8a82bd4bef91d08da45cdc0"
+dependencies = [
+ "autocfg",
+ "num-integer",
+ "num-traits",
+]
+
+[[package]]
+name = "num-format"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a652d9771a63711fd3c3deb670acfbe5c30a4072e664d7a3bf5a9e1056ac72c3"
+dependencies = [
+ "arrayvec",
+ "itoa",
+]
+
+[[package]]
+name = "num-integer"
+version = "0.1.46"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7969661fd2958a5cb096e56c8e1ad0444ac2bbcd0061bd28660485a44879858f"
+dependencies = [
+ "num-traits",
+]
+
+[[package]]
+name = "num-rational"
+version = "0.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0638a1c9d0a3c0914158145bc76cff373a75a627e6ecbfb71cbe6f453a5a19b0"
+dependencies = [
+ "autocfg",
+ "num-bigint",
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.18"
@@ -995,6 +1170,43 @@ dependencies = [
  "autocfg",
 ]
 
+[[package]]
+name = "numbat"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a54ccd3e33759b0171c20adfa0d8b0d2709fe131067faabcfcc1c35621a30b4b"
+dependencies = [
+ "chrono",
+ "chrono-tz",
+ "codespan-reporting",
+ "heck",
+ "iana-time-zone",
+ "itertools",
+ "libc",
+ "num-format",
+ "num-integer",
+ "num-rational",
+ "num-traits",
+ "numbat-exchange-rates",
+ "pretty_dtoa",
+ "rust-embed",
+ "strsim",
+ "thiserror",
+ "unicode-ident",
+ "unicode-width",
+ "walkdir",
+]
+
+[[package]]
+name = "numbat-exchange-rates"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fd1e3c3e4f9f22d0d7cdcb413f01194f6506a302a9029d95deedcd1c25df7718"
+dependencies = [
+ "attohttpc",
+ "quick-xml",
+]
+
 [[package]]
 name = "object"
 version = "0.32.2"
@@ -1010,6 +1222,12 @@ version = "1.19.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3fdb12b2476b595f9358c5161aa467c2438859caa136dec86c26fdd2efe17b92"
 
+[[package]]
+name = "option-ext"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "04744f49eae99ab78e0d5c0b603ab218f515ea8cfe5a456d7629ad883a3b6e7d"
+
 [[package]]
 name = "parking_lot"
 version = "0.12.1"
@@ -1183,6 +1401,15 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
 
+[[package]]
+name = "pretty_dtoa"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a239bcdfda2c685fda1add3b4695c06225f50075e3cfb5b954e91545587edff2"
+dependencies = [
+ "ryu_floating_decimal",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.79"
@@ -1192,6 +1419,15 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "quick-xml"
+version = "0.31.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1004a344b30a54e2ee58d66a71b32d2db2feb0a31f9a2d302bf0536f15de2a33"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "quote"
 version = "1.0.35"
@@ -1240,6 +1476,17 @@ dependencies = [
  "bitflags 1.3.2",
 ]
 
+[[package]]
+name = "redox_users"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bd283d9651eeda4b2a83a43c1c91b266c40fd76ecd39a50a8c630ae69dc72891"
+dependencies = [
+ "getrandom",
+ "libredox",
+ "thiserror",
+]
+
 [[package]]
 name = "regex"
 version = "1.10.3"
@@ -1293,7 +1540,7 @@ dependencies = [
  "once_cell",
  "percent-encoding",
  "pin-project-lite",
- "rustls",
+ "rustls 0.21.10",
  "rustls-pemfile",
  "serde",
  "serde_json",
@@ -1308,7 +1555,7 @@ dependencies = [
  "wasm-bindgen",
  "wasm-bindgen-futures",
  "web-sys",
- "webpki-roots",
+ "webpki-roots 0.25.4",
  "winreg",
 ]
 
@@ -1327,6 +1574,41 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "rust-embed"
+version = "8.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fb78f46d0066053d16d4ca7b898e9343bc3530f71c61d5ad84cd404ada068745"
+dependencies = [
+ "rust-embed-impl",
+ "rust-embed-utils",
+ "walkdir",
+]
+
+[[package]]
+name = "rust-embed-impl"
+version = "8.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b91ac2a3c6c0520a3fb3dd89321177c3c692937c4eb21893378219da10c44fc8"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "rust-embed-utils",
+ "shellexpand",
+ "syn 2.0.52",
+ "walkdir",
+]
+
+[[package]]
+name = "rust-embed-utils"
+version = "8.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86f69089032567ffff4eada41c573fc43ff466c7db7c5688b2e7969584345581"
+dependencies = [
+ "sha2",
+ "walkdir",
+]
+
 [[package]]
 name = "rustc-demangle"
 version = "0.1.23"
@@ -1341,10 +1623,24 @@ checksum = "f9d5a6813c0759e4609cd494e8e725babae6a2ca7b62a5536a13daaec6fcb7ba"
 dependencies = [
  "log",
  "ring",
- "rustls-webpki",
+ "rustls-webpki 0.101.7",
  "sct",
 ]
 
+[[package]]
+name = "rustls"
+version = "0.22.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "99008d7ad0bbbea527ec27bddbc0e432c5b87d8175178cee68d2eec9c4a1813c"
+dependencies = [
+ "log",
+ "ring",
+ "rustls-pki-types",
+ "rustls-webpki 0.102.2",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "rustls-pemfile"
 version = "1.0.4"
@@ -1354,6 +1650,12 @@ dependencies = [
  "base64 0.21.7",
 ]
 
+[[package]]
+name = "rustls-pki-types"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ecd36cc4259e3e4514335c4a138c6b43171a8d61d8f5c9348f9fc7529416f247"
+
 [[package]]
 name = "rustls-webpki"
 version = "0.101.7"
@@ -1364,6 +1666,17 @@ dependencies = [
  "untrusted",
 ]
 
+[[package]]
+name = "rustls-webpki"
+version = "0.102.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "faaa0a62740bedb9b2ef5afa303da42764c012f743917351dc9a237ea1663610"
+dependencies = [
+ "ring",
+ "rustls-pki-types",
+ "untrusted",
+]
+
 [[package]]
 name = "rustversion"
 version = "1.0.14"
@@ -1376,6 +1689,21 @@ version = "1.0.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e86697c916019a8588c99b5fac3cead74ec0b4b819707a682fd4d23fa0ce1ba1"
 
+[[package]]
+name = "ryu_floating_decimal"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "700de91d5fd6091442d00fdd9ee790af6d4f0f480562b0f5a1e8f59e90aafe73"
+
+[[package]]
+name = "same-file"
+version = "1.0.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "93fc1dc3aaa9bfed95e02e6eadabb4baf7e3078b0bd1b4d7b6b0b68378900502"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "scopeguard"
 version = "1.2.0"
@@ -1498,6 +1826,26 @@ dependencies = [
  "stable_deref_trait",
 ]
 
+[[package]]
+name = "sha2"
+version = "0.10.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "793db75ad2bcafc3ffa7c68b215fee268f537982cd901d132f89c6343f3a3dc8"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest",
+]
+
+[[package]]
+name = "shellexpand"
+version = "3.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da03fa3b94cc19e3ebfc88c4229c49d8f08cdbd1228870a45f0ffdf84988e14b"
+dependencies = [
+ "dirs",
+]
+
 [[package]]
 name = "siphasher"
 version = "0.3.11"
@@ -1567,6 +1915,18 @@ dependencies = [
  "quote",
 ]
 
+[[package]]
+name = "strsim"
+version = "0.11.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7da8b5736845d9f2fcb837ea5d9e2628564b3b043a70948a3f0b778838c5fb4f"
+
+[[package]]
+name = "subtle"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "81cdd64d312baedb58e21336b31bc043b77e01cc99033ce76ef539f78e965ebc"
+
 [[package]]
 name = "syn"
 version = "1.0.109"
@@ -1627,6 +1987,35 @@ dependencies = [
  "utf-8",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "06794f8f6c5c898b3275aebefa6b8a1cb24cd2c6c79397ab15774837a0bc5755"
+dependencies = [
+ "winapi-util",
+]
+
+[[package]]
+name = "thiserror"
+version = "1.0.58"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "03468839009160513471e86a034bb2c5c0e4baae3b43f79ffc55c4a5427b3297"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.58"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c61f3ba182994efc43764a46c018c347bc492c79f024e705f46567b418f6d4f7"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.52",
+]
+
 [[package]]
 name = "tinyvec"
 version = "1.6.0"
@@ -1675,7 +2064,7 @@ version = "0.24.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c28327cf380ac148141087fbfb9de9d7bd4e84ab5d2c28fbc911d753de8a7081"
 dependencies = [
- "rustls",
+ "rustls 0.21.10",
  "tokio",
 ]
 
@@ -1790,6 +2179,12 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
+[[package]]
+name = "typenum"
+version = "1.17.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42ff0bf0c66b8238c6f3b578df37d0b7848e55df8577b3f74f92a69acceeb825"
+
 [[package]]
 name = "uncased"
 version = "0.9.10"
@@ -1820,6 +2215,12 @@ dependencies = [
  "tinyvec",
 ]
 
+[[package]]
+name = "unicode-segmentation"
+version = "1.11.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d4c87d22b6e3f4a18d4d40ef354e97c90fcb14dd91d7dc0aa9d8a1172ebf7202"
+
 [[package]]
 name = "unicode-width"
 version = "0.1.11"
@@ -1867,6 +2268,16 @@ version = "0.9.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "49874b5167b65d7193b8aba1567f5c7d93d001cafc34600cee003eda787e483f"
 
+[[package]]
+name = "walkdir"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "29790946404f91d9c5d06f9874efddea1dc06c5efe94541a7d6863108e3a5e4b"
+dependencies = [
+ "same-file",
+ "winapi-util",
+]
+
 [[package]]
 name = "want"
 version = "0.3.1"
@@ -1964,6 +2375,46 @@ version = "0.25.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5f20c57d8d7db6d3b86154206ae5d8fba62dd39573114de97c2cb0578251f8e1"
 
+[[package]]
+name = "webpki-roots"
+version = "0.26.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3de34ae270483955a94f4b21bdaaeb83d508bb84a01435f393818edb0012009"
+dependencies = [
+ "rustls-pki-types",
+]
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-util"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f29e6f9198ba0d26b4c9f07dbe6f9ed633e1f3d5b8b414090084349e46a52596"
+dependencies = [
+ "winapi",
+]
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
+
 [[package]]
 name = "windows-core"
 version = "0.52.0"
@@ -2143,3 +2594,9 @@ dependencies = [
  "quote",
  "syn 2.0.52",
 ]
+
+[[package]]
+name = "zeroize"
+version = "1.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "525b4ec142c6b68a2d10f01f7bbf6755599ca3f81ea53b8431b7dd348f5fdb2d"
diff --git a/Cargo.toml b/Cargo.toml
index bdf02c7..a5abf8e 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,7 @@ eyre = "0.6.12"
 fend-core = "1.4.5"
 futures = "0.3.30"
 html-escape = "0.2.13"
+numbat = "1.11.0"
 once_cell = "1.19.0"
 rand = "0.8.5"
 regex = "1.10.3"
diff --git a/README b/README
index 637ddfc..bc3586c 100644
--- a/README
+++ b/README
@@ -14,7 +14,7 @@ build it with `cargo b -r`, the resulting binary will be at
 `target/release/metasearch2`.
 
 the config.toml file is created in your current working directory on the first
-run of metasearch2. alternatively, you can copy the example-config.toml in the
+run of metasearch2. alternatively, you can copy the default-config.toml in the
 repo and rename it to config.toml.
 
 the default port is port 28019.
diff --git a/default-config.toml b/default-config.toml
index acfd3c6..899cbfa 100644
--- a/default-config.toml
+++ b/default-config.toml
@@ -5,6 +5,10 @@ google = { weight = 1.05 }
 bing = { weight = 1.0 }
 brave = { weight = 1.25 }
 
+# calculators (give them a high weight so they're always the first thing in autocomplete)
+numbat = { weight = 10 }
+fend = { enabled = false, weight = 10 }
+
 [engines.marginalia]
 args = { profile = "corpo", js = "default", adtech = "default" }
 weight = 0.15
diff --git a/src/engines/answer.rs b/src/engines/answer.rs
index b4b998b..3d60649 100644
--- a/src/engines/answer.rs
+++ b/src/engines/answer.rs
@@ -1,6 +1,7 @@
-pub mod calc;
 pub mod dictionary;
+pub mod fend;
 pub mod ip;
+pub mod numbat;
 pub mod thesaurus;
 pub mod timezone;
 pub mod useragent;
diff --git a/src/engines/answer/calc.rs b/src/engines/answer/fend.rs
similarity index 100%
rename from src/engines/answer/calc.rs
rename to src/engines/answer/fend.rs
diff --git a/src/engines/answer/numbat.rs b/src/engines/answer/numbat.rs
new file mode 100644
index 0000000..4b1da02
--- /dev/null
+++ b/src/engines/answer/numbat.rs
@@ -0,0 +1,196 @@
+use std::collections::HashSet;
+
+use fend_core::SpanKind;
+use numbat::{
+    markup::{FormatType, FormattedString, Markup},
+    pretty_print::PrettyPrint,
+    resolver::CodeSource,
+    InterpreterResult, InterpreterSettings, Statement,
+};
+use once_cell::sync::Lazy;
+
+use crate::engines::EngineResponse;
+
+pub fn request(query: &str) -> EngineResponse {
+    let query = clean_query(query);
+
+    let Some(NumbatResponse {
+        query_html,
+        result_html,
+    }) = evaluate(&query)
+    else {
+        return EngineResponse::new();
+    };
+
+    EngineResponse::answer_html(format!(
+        r#"<p class="answer-query">{query_html} =</p>
+<h3><b>{result_html}</b></h3>"#
+    ))
+}
+
+pub fn request_autocomplete(query: &str) -> Vec<String> {
+    let mut results = Vec::new();
+
+    let query = clean_query(query);
+
+    if let Some(result) = evaluate_for_autocomplete(&query) {
+        results.push(format!("= {result}"));
+    }
+
+    results
+}
+
+fn clean_query(query: &str) -> String {
+    query.strip_suffix('=').unwrap_or(query).trim().to_string()
+}
+
+#[derive(Debug)]
+pub struct Span {
+    pub text: String,
+    pub kind: SpanKind,
+}
+
+fn is_potential_request(query: &str) -> bool {
+    // allow these short constants, they're fine
+    if matches!(query.to_lowercase().as_str(), "pi" | "e" | "c") {
+        return true;
+    }
+
+    // at least 3 characters
+    if query.len() < 3 {
+        return false;
+    }
+
+    // must have numbers
+    if !query.chars().any(|c| c.is_numeric()) {
+        return false;
+    }
+
+    // if it starts and ends with quotes then the person was just searching in
+    // quotes and didn't mean to evaluate a string
+    if query.starts_with('"')
+        && query.ends_with('"')
+        && query.chars().filter(|c| *c == '"').count() == 2
+    {
+        return false;
+    }
+
+    true
+}
+
+fn interpret(query: &str) -> Option<(Statement, InterpreterResult)> {
+    if !is_potential_request(query) {
+        return None;
+    }
+
+    let mut ctx = NUMBAT_CTX.clone();
+
+    let (statements, res) = match ctx.interpret_with_settings(
+        &mut InterpreterSettings {
+            print_fn: Box::new(move |_: &Markup| {}),
+        },
+        query,
+        CodeSource::Text,
+    ) {
+        Ok(r) => r,
+        Err(_) => {
+            return None;
+        }
+    };
+
+    Some((statements.into_iter().last()?, res))
+}
+
+fn evaluate_for_autocomplete(query: &str) -> Option<String> {
+    let (_statements, res) = interpret(query)?;
+
+    let res_markup = match res {
+        InterpreterResult::Value(val) => val.pretty_print(),
+        InterpreterResult::Continue => return None,
+    };
+
+    Some(res_markup.to_string())
+}
+
+pub struct NumbatResponse {
+    pub query_html: String,
+    pub result_html: String,
+}
+
+fn evaluate(query: &str) -> Option<NumbatResponse> {
+    let (statement, res) = interpret(query)?;
+
+    let res_markup = match res {
+        InterpreterResult::Value(val) => val.pretty_print(),
+        InterpreterResult::Continue => return None,
+    };
+
+    let statement_markup = statement.pretty_print();
+    let query_html = markup_to_html(statement_markup);
+    let result_html = markup_to_html(res_markup);
+
+    Some(NumbatResponse {
+        query_html,
+        result_html,
+    })
+}
+
+fn markup_to_html(markup: Markup) -> String {
+    let mut html = String::new();
+    for FormattedString(_output_type, format_type, content) in markup.0 {
+        let class = match format_type {
+            FormatType::Value => "answer-calc-constant",
+            FormatType::String => "answer-calc-string",
+            FormatType::Identifier => "answer-calc-func",
+            _ => "",
+        };
+        if class.is_empty() {
+            html.push_str(&html_escape::encode_safe(&content));
+        } else {
+            html.push_str(&format!(
+                r#"<span class="{class}">{content}</span>"#,
+                content = html_escape::encode_safe(&content)
+            ));
+        }
+    }
+    html
+}
+
+pub static NUMBAT_CTX: Lazy<numbat::Context> = Lazy::new(|| {
+    let mut ctx = numbat::Context::new(numbat::module_importer::BuiltinModuleImporter {});
+    let _ = ctx.interpret("use prelude", CodeSource::Internal);
+    let _ = ctx.interpret("use units::currencies", CodeSource::Internal);
+
+    ctx.load_currency_module_on_demand(true);
+
+    // a few hardcoded aliases
+    // (the lowercase alias code won't work for these because they have prefixes)
+    for (alias, canonical) in &[
+        ("kb", "kB"),
+        ("mb", "MB"),
+        ("gb", "GB"),
+        ("tb", "TB"),
+        ("pb", "PB"),
+    ] {
+        let _ = ctx.interpret(&format!("unit {alias} = {canonical}"), CodeSource::Internal);
+    }
+
+    // lowercase aliases (so for example usd and USD are the same unit)
+
+    let mut unit_names = HashSet::new();
+    for names in ctx.unit_names() {
+        unit_names.extend(names.iter().map(|name| name.to_owned()));
+    }
+
+    for name in &unit_names {
+        // taken_unit_names.insert(alias_name);
+        let name_lower = name.to_lowercase();
+        // add every lowercase aliases for every unit as long as that alias isn't
+        // already taken
+        if !unit_names.contains(&name_lower) {
+            let _ = ctx.interpret(&format!("unit {name_lower} = {name}"), CodeSource::Internal);
+        }
+    }
+
+    ctx
+});
diff --git a/src/engines/mod.rs b/src/engines/mod.rs
index fba4a2e..5d6d21c 100644
--- a/src/engines/mod.rs
+++ b/src/engines/mod.rs
@@ -33,7 +33,8 @@ engines! {
     // answer
     Useragent = "useragent",
     Ip = "ip",
-    Calc = "calc",
+    Fend = "fend",
+    Numbat = "numbat",
     Wikipedia = "wikipedia",
     Dictionary = "dictionary",
     Thesaurus = "thesaurus",
@@ -53,7 +54,8 @@ engine_requests! {
     // answer
     Useragent => answer::useragent::request, None,
     Ip => answer::ip::request, None,
-    Calc => answer::calc::request, None,
+    Fend => answer::fend::request, None,
+    Numbat => answer::numbat::request, None,
     Wikipedia => answer::wikipedia::request, parse_response,
     Dictionary => answer::dictionary::request, parse_response,
     Thesaurus => answer::thesaurus::request, parse_response,
@@ -62,7 +64,8 @@ engine_requests! {
 
 engine_autocomplete_requests! {
     Google => search::google::request_autocomplete, parse_autocomplete_response,
-    Calc => answer::calc::request_autocomplete, None,
+    Fend => answer::fend::request_autocomplete, None,
+    Numbat => answer::numbat::request_autocomplete, None,
 }
 
 engine_postsearch_requests! {
diff --git a/src/web/assets/style.css b/src/web/assets/style.css
index 2bdd5ba..fce2b68 100644
--- a/src/web/assets/style.css
+++ b/src/web/assets/style.css
@@ -26,6 +26,7 @@
   --syntax-special: #e6b673;
   --syntax-constant: #d2a6ff;
   --syntax-comment: #acb6bf8c;
+  --syntax-func: #ffb454;
 }
 
 html {
@@ -237,6 +238,9 @@ h1 {
 .answer-calc-special {
   color: var(--syntax-special);
 }
+.answer-calc-func {
+  color: var(--syntax-func);
+}
 
 .answer-dictionary-word,
 .answer-thesaurus-word {