Add builtin functions for calc

examples/calc/AST.cpp

@@ -1,9 +1,43 @@
 #include "AST.h"
 
 #include <cmath>
+#include <functional>
+#include <map>
+#include <string>
 
 namespace calc {
 
+namespace {
+    using d2dfn = double(*)(double);
+    std::function<double(const Variables&, const Functions&, FunctionArguments&)> wrap(std::function<double(double)> fn) {
+        return [fn](const Variables& vars, const Functions& funs, FunctionArguments& args) -> double{
+            if (args.size() != 1)
+                return 0;
+            return fn(args[0]->eval(vars, funs));
+        };
+    }
+
+    std::map<std::string, std::function<double(const Variables&, const Functions&, FunctionArguments&)>> builtins = 
+    {
+        {"if", [](const Variables& vars, const Functions& funs, FunctionArguments& args) -> double {
+            if (args.size() != 3)
+                return 0;
+            double test = args[0]->eval(vars, funs);
+            if (std::fabs(test) < 1e-8)
+                return args[2]->eval(vars, funs);
+            else
+                return args[1]->eval(vars, funs);
+        }},
+        {"sin", wrap((d2dfn)(std::sin))},
+        {"cos", wrap((d2dfn)(std::cos))},
+        {"tan", wrap((d2dfn)(std::tan))},
+        {"asin", wrap((d2dfn)(std::asin))},
+        {"acos", wrap((d2dfn)(std::acos))},
+        {"atan", wrap((d2dfn)(std::atan))},
+        {"abs", wrap((d2dfn)(std::fabs))}
+    };
+}
+
 Number::Number(double d) : m_val(d) {}
 double Number::eval(const Variables&, const Functions&) const {
     return m_val;
@@ -74,8 +108,13 @@ std::size_t FunctionArguments::size() const {
 FunctionCall::FunctionCall(std::string name, std::unique_ptr<FunctionArguments>&& arguments) : m_name(name), m_arguments(std::move(arguments)) {}
 double FunctionCall::eval(const Variables& vars, const Functions& funs) const {
     auto fp = funs.find(m_name);
-    if (fp == funs.end())
+    if (fp == funs.end()) {
-        return 0;
+        if (builtins.count(m_name)) {
+            return builtins[m_name](vars, funs, *m_arguments);
+        } else {
+            return 0;
+        }
+    }
     Function& fun = *dynamic_cast<Function*>((fp->second.get()));
 
     if (m_arguments->size() != fun.getParams().size()) return 0;