From 7e60437d3c064bca402d486be967c43bf4326067 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom@tomsmeding.com>
Date: Wed, 3 Sep 2025 23:31:40 +0200
Subject: Initial (with old code)

This includes old code too, perhaps from 2021-05-05, judging from the
birth timestamp on the directory. The old code included option parsing
and equation solving for fancy mutually-dependent options, but no actual
rendering (imagine that).
---
 eqsystem_solve.h | 62 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 62 insertions(+)
 create mode 100644 eqsystem_solve.h

(limited to 'eqsystem_solve.h')

diff --git a/eqsystem_solve.h b/eqsystem_solve.h
new file mode 100644
index 0000000..34cd4cc
--- /dev/null
+++ b/eqsystem_solve.h
@@ -0,0 +1,62 @@
+#pragma once
+
+#include <optional>
+#include <string>
+#include <variant>
+#include <vector>
+
+
+struct Product {
+	double cnst;
+	std::vector<std::string> vars;
+
+	const Product times(double x) const;
+	void times_inplace(double x);
+	const Product times(const Product &p) const;
+	bool contains(const std::string &var) const;
+	const Product without(const std::string &var) const;
+
+	bool operator==(const Product &other) const;
+};
+
+struct Sum {
+	std::vector<Product> terms;
+
+	const Sum times(double x) const;
+	const Sum substitute(const std::string &var, Sum sum) const;
+	void simplify();
+	// Returns std::nullopt if there are variables in the terms
+	std::optional<double> evaluate() const;
+};
+
+// An equation is not allowed to contain a variable name more than once.
+struct Equation {
+	Sum lhs, rhs;
+
+	std::optional<std::string> validate() const;
+	const Equation substitute(const std::string &var, Sum sum) const;
+	void substitute_inplace(const std::string &var, Sum sum);
+	int num_vars() const;
+	std::vector<std::string> all_vars() const;
+	bool isolatable(const std::string &target) const;
+	void isolate_left(const std::string &target);
+	void simplify();
+};
+
+struct System {
+	std::vector<Equation> eqs;
+
+	std::variant<
+		std::string,  // description of the error
+		std::vector<std::pair<std::string, double>>  // result assignment
+	> solve_inplace(bool debug);
+
+	void substitute_inplace(const std::string &var, Sum sum);
+};
+
+std::ostream& operator<<(std::ostream &os, const Product &p);
+std::ostream& operator<<(std::ostream &os, const Sum &s);
+std::ostream& operator<<(std::ostream &os, const Equation &eq);
+std::ostream& operator<<(std::ostream &os, const System &sys);
+
+// vim: set sw=4 ts=4 noet:
-- 
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