Add math expression evaluation to NumberInput boxes (#1472)

* Add math expression parsing to NumberInput boxes

* Prevent NaN results

* Add support for implicit multiplication in expressions

Cargo.lock

@@ -2286,6 +2286,7 @@ dependencies = [
  "graphite-editor",
  "js-sys",
  "log",
+ "meval",
  "ron",
  "serde",
  "serde-wasm-bindgen",
@@ -3101,9 +3102,9 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.5.0"
+version = "2.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+checksum = "f665ee40bc4a3c5590afb1e9677db74a508659dfd71e126420da8274909a0167"
 
 [[package]]
 name = "memmap2"
@@ -3165,6 +3166,16 @@ dependencies = [
  "paste",
 ]
 
+[[package]]
+name = "meval"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f79496a5651c8d57cd033c5add8ca7ee4e3d5f7587a4777484640d9cb60392d9"
+dependencies = [
+ "fnv",
+ "nom 1.2.4",
+]
+
 [[package]]
 name = "mime"
 version = "0.3.17"
@@ -3401,6 +3412,12 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
 
+[[package]]
+name = "nom"
+version = "1.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5b8c256fd9471521bcb84c3cdba98921497f1a331cbc15b8030fc63b82050ce"
+
 [[package]]
 name = "nom"
 version = "7.1.3"
@@ -4340,14 +4357,14 @@ dependencies = [
 
 [[package]]
 name = "regex"
-version = "1.9.3"
+version = "1.10.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "81bc1d4caf89fac26a70747fe603c130093b53c773888797a6329091246d651a"
+checksum = "380b951a9c5e80ddfd6136919eef32310721aa4aacd4889a8d39124b026ab343"
 dependencies = [
  "aho-corasick",
  "memchr",
- "regex-automata 0.3.6",
+ "regex-automata 0.4.3",
- "regex-syntax 0.7.4",
+ "regex-syntax 0.8.2",
 ]
 
 [[package]]
@@ -4361,13 +4378,13 @@ dependencies = [
 
 [[package]]
 name = "regex-automata"
-version = "0.3.6"
+version = "0.4.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fed1ceff11a1dddaee50c9dc8e4938bd106e9d89ae372f192311e7da498e3b69"
+checksum = "5f804c7828047e88b2d32e2d7fe5a105da8ee3264f01902f796c8e067dc2483f"
 dependencies = [
  "aho-corasick",
  "memchr",
- "regex-syntax 0.7.4",
+ "regex-syntax 0.8.2",
 ]
 
 [[package]]
@@ -4378,9 +4395,9 @@ checksum = "f162c6dd7b008981e4d40210aca20b4bd0f9b60ca9271061b07f78537722f2e1"
 
 [[package]]
 name = "regex-syntax"
-version = "0.7.4"
+version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e5ea92a5b6195c6ef2a0295ea818b312502c6fc94dde986c5553242e18fd4ce2"
+checksum = "c08c74e62047bb2de4ff487b251e4a92e24f48745648451635cec7d591162d9f"
 
 [[package]]
 name = "remain"
@@ -7466,7 +7483,7 @@ version = "0.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "463705a63313cd4301184381c5e8042f0a7e9b4bb63653f216311d4ae74690b7"
 dependencies = [
- "nom",
+ "nom 7.1.3",
 ]
 
 [[package]]

frontend/src/components/widgets/inputs/NumberInput.svelte

@@ -2,6 +2,7 @@
 	import { createEventDispatcher, onMount, onDestroy } from "svelte";
 
 	import { type NumberInputMode, type NumberInputIncrementBehavior } from "@graphite/wasm-communication/messages";
+	import { evaluateMathExpression } from "@graphite-frontend/wasm/pkg/graphite_wasm.js";
 
 	import FieldInput from "@graphite/components/widgets/inputs/FieldInput.svelte";
 
@@ -185,13 +186,11 @@
 		// The `unFocus()` call at the bottom of this function and in `onTextChangeCanceled()` causes this function to be run again, so this check skips a second run.
 		if (!editing) return;
 
-		const parsed = parseFloat(text);
+		let newValue = evaluateMathExpression(text);
-		const newValue = Number.isNaN(parsed) ? undefined : parsed;
+		if (newValue !== undefined && isNaN(newValue)) newValue = undefined; // Rejects `sqrt(-1)`
-
 		updateValue(newValue);
 
 		editing = false;
-
 		self?.unFocus();
 	}
 

frontend/wasm/Cargo.toml

@@ -37,6 +37,7 @@ ron = { version = "0.8", optional = true }
 bezier-rs = { path = "../../libraries/bezier-rs" }
 # We don't have wgpu on multiple threads (yet) https://github.com/gfx-rs/wgpu/blob/trunk/CHANGELOG.md#wgpu-types-now-send-sync-on-wasm
 wgpu = { version = "0.17", features = ["fragile-send-sync-non-atomic-wasm"] }
+meval = "0.2.0"
 
 [dependencies.web-sys]
 version = "0.3.4"

frontend/wasm/src/editor_api.rs

@@ -755,3 +755,86 @@ impl Drop for JsEditorHandle {
 		EDITOR_INSTANCES.with(|instances| instances.borrow_mut().remove(&self.editor_id));
 	}
 }
+
+#[wasm_bindgen(js_name = evaluateMathExpression)]
+pub fn evaluate_math_expression(expression: &str) -> Option<f64> {
+	// TODO: Rewrite our own purpose-built math expression parser that supports unit conversions.
+
+	let mut context = meval::Context::new();
+	context.var("tau", std::f64::consts::TAU);
+	context.func("log", f64::log10);
+	context.func("log10", f64::log10);
+	context.func("log2", f64::log2);
+
+	// Insert asterisks where implicit multiplication is used in the expression string
+	let expression = implicit_multiplication_preprocess(expression);
+
+	meval::eval_str_with_context(&expression, &context).ok()
+}
+
+// Modified from this public domain snippet: <https://gist.github.com/Titaniumtown/c181be5d06505e003d8c4d1e372684ff>
+// Discussion: <https://github.com/rekka/meval-rs/issues/28#issuecomment-1826381922>
+pub fn implicit_multiplication_preprocess(expression: &str) -> String {
+	let function = expression.to_lowercase().replace("log10(", "log(").replace("log2(", "logtwo(").replace("pi", "π").replace("tau", "τ");
+	let valid_variables: Vec<char> = "eπτ".chars().collect();
+	let letters: Vec<char> = ('a'..='z').chain('A'..='Z').collect();
+	let numbers: Vec<char> = ('0'..='9').collect();
+	let function_chars: Vec<char> = function.chars().collect();
+	let mut output_string: String = String::new();
+	let mut prev_chars: Vec<char> = Vec::new();
+
+	for c in function_chars {
+		let mut add_asterisk: bool = false;
+		let prev_chars_len = prev_chars.len();
+
+		let prev_prev_char = if prev_chars_len >= 2 { *prev_chars.get(prev_chars_len - 2).unwrap() } else { ' ' };
+
+		let prev_char = if prev_chars_len >= 1 { *prev_chars.get(prev_chars_len - 1).unwrap() } else { ' ' };
+
+		let c_letters_var = letters.contains(&c) | valid_variables.contains(&c);
+		let prev_letters_var = valid_variables.contains(&prev_char) | letters.contains(&prev_char);
+
+		if prev_char == ')' {
+			if (c == '(') | numbers.contains(&c) | c_letters_var {
+				add_asterisk = true;
+			}
+		} else if c == '(' {
+			if (valid_variables.contains(&prev_char) | (')' == prev_char) | numbers.contains(&prev_char)) && !letters.contains(&prev_prev_char) {
+				add_asterisk = true;
+			}
+		} else if numbers.contains(&prev_char) {
+			if (c == '(') | c_letters_var {
+				add_asterisk = true;
+			}
+		} else if letters.contains(&c) {
+			if numbers.contains(&prev_char) | (valid_variables.contains(&prev_char) && valid_variables.contains(&c)) {
+				add_asterisk = true;
+			}
+		} else if (numbers.contains(&c) | c_letters_var) && prev_letters_var {
+			add_asterisk = true;
+		}
+
+		if add_asterisk {
+			output_string += "*";
+		}
+
+		prev_chars.push(c);
+		output_string += &c.to_string();
+	}
+
+	// We have to convert the Greek symbols back to ASCII because meval doesn't support unicode symbols as context constants
+	output_string.replace("logtwo(", "log2(").replace("π", "pi").replace("τ", "tau")
+}
+
+#[test]
+fn implicit_multiplication_preprocess_tests() {
+	assert_eq!(implicit_multiplication_preprocess("2pi"), "2*pi");
+	assert_eq!(implicit_multiplication_preprocess("sin(2pi)"), "sin(2*pi)");
+	assert_eq!(implicit_multiplication_preprocess("2sin(pi)"), "2*sin(pi)");
+	assert_eq!(implicit_multiplication_preprocess("2sin(3(4 + 5))"), "2*sin(3*(4 + 5))");
+	assert_eq!(implicit_multiplication_preprocess("3abs(-4)"), "3*abs(-4)");
+	assert_eq!(implicit_multiplication_preprocess("-1(4)"), "-1*(4)");
+	assert_eq!(implicit_multiplication_preprocess("(-1)4"), "(-1)*4");
+	assert_eq!(implicit_multiplication_preprocess("(((-1)))(4)"), "(((-1)))*(4)");
+	assert_eq!(implicit_multiplication_preprocess("2sin(pi) + 2cos(tau)"), "2*sin(pi) + 2*cos(tau)");
+}