From 4e76c6e7087b9682e5f07d4dba3d91d6f7e0a966 Mon Sep 17 00:00:00 2001
From: Sam Hocevar <sam@hocevar.net>
Date: Fri, 16 Jan 2015 15:41:07 +0000
Subject: [PATCH] lolremez: shorter code in the expression parser.
---
tools/lolremez/expression.h | 157 +++++++++++++-----------------------
1 file changed, 58 insertions(+), 99 deletions(-)
diff --git a/tools/lolremez/expression.h b/tools/lolremez/expression.h
index f8834914..ba9ad48f 100644
--- a/tools/lolremez/expression.h
+++ b/tools/lolremez/expression.h
@@ -13,7 +13,12 @@
#pragma once
//
-// Parser tools for a simple calculator grammar with + - * /
+// Powerful arithmetic expression parser/evaluator
+//
+// Usage:
+// expression e;
+// e.parse(" 2*x^3 + 3 * sin(x - atan(x))");
+// auto y = e.eval("1.5");
//
#include "pegtl.hh"
@@ -85,114 +90,68 @@ struct expression
*/
lol::real eval(lol::real const &x) const
{
+ /* Use a stack */
lol::array<lol::real> stack;
- lol::real tmp;
for (int i = 0; i < m_ops.Count(); ++i)
{
- switch (m_ops[i].m1)
+ /* Rules that do not consume stack elements */
+ if (m_ops[i].m1 == op::x)
{
- case op::plus:
- break;
- case op::minus:
- stack.Push(-stack.Pop());
- break;
- case op::abs:
- stack.Push(fabs(stack.Pop()));
- break;
- case op::sqrt:
- stack.Push(sqrt(stack.Pop()));
- break;
- case op::cbrt:
- stack.Push(cbrt(stack.Pop()));
- break;
- case op::exp:
- stack.Push(exp(stack.Pop()));
- break;
- case op::exp2:
- stack.Push(exp2(stack.Pop()));
- break;
- case op::log:
- stack.Push(log(stack.Pop()));
- break;
- case op::log2:
- stack.Push(log2(stack.Pop()));
- break;
- case op::log10:
- stack.Push(log10(stack.Pop()));
- break;
- case op::sin:
- stack.Push(sin(stack.Pop()));
- break;
- case op::cos:
- stack.Push(cos(stack.Pop()));
- break;
- case op::tan:
- stack.Push(tan(stack.Pop()));
- break;
- case op::asin:
- stack.Push(asin(stack.Pop()));
- break;
- case op::acos:
- stack.Push(acos(stack.Pop()));
- break;
- case op::atan:
- stack.Push(atan(stack.Pop()));
- break;
- case op::sinh:
- stack.Push(sinh(stack.Pop()));
- break;
- case op::cosh:
- stack.Push(cosh(stack.Pop()));
- break;
- case op::tanh:
- stack.Push(tanh(stack.Pop()));
- break;
+ stack.push(x);
+ continue;
+ }
+ else if (m_ops[i].m1 == op::constant)
+ {
+ stack.push(m_constants[m_ops[i].m2]);
+ continue;
+ }
- case op::add:
- tmp = stack.Pop();
- stack.Push(stack.Pop() + tmp);
- break;
- case op::sub:
- tmp = stack.Pop();
- stack.Push(stack.Pop() - tmp);
- break;
- case op::mul:
- tmp = stack.Pop();
- stack.Push(stack.Pop() * tmp);
- break;
- case op::div:
- tmp = stack.Pop();
- stack.Push(stack.Pop() / tmp);
- break;
- case op::atan2:
- tmp = stack.Pop();
- stack.Push(atan2(stack.Pop(), tmp));
- break;
- case op::pow:
- tmp = stack.Pop();
- stack.Push(pow(stack.Pop(), tmp));
- break;
- case op::min:
- tmp = stack.Pop();
- stack.Push(min(stack.Pop(), tmp));
- break;
- case op::max:
- tmp = stack.Pop();
- stack.Push(max(stack.Pop(), tmp));
- break;
+ /* All other rules consume at least the head of the stack */
+ lol::real head = stack.pop();
- case op::x:
- stack.Push(x);
- break;
+ switch (m_ops[i].m1)
+ {
+ case op::plus: stack.push(head); break;
+ case op::minus: stack.push(-head); break;
+
+ case op::abs: stack.push(fabs(head)); break;
+ case op::sqrt: stack.push(sqrt(head)); break;
+ case op::cbrt: stack.push(cbrt(head)); break;
+ case op::exp: stack.push(exp(head)); break;
+ case op::exp2: stack.push(exp2(head)); break;
+ case op::log: stack.push(log(head)); break;
+ case op::log2: stack.push(log2(head)); break;
+ case op::log10: stack.push(log10(head)); break;
+ case op::sin: stack.push(sin(head)); break;
+ case op::cos: stack.push(cos(head)); break;
+ case op::tan: stack.push(tan(head)); break;
+ case op::asin: stack.push(asin(head)); break;
+ case op::acos: stack.push(acos(head)); break;
+ case op::atan: stack.push(atan(head)); break;
+ case op::sinh: stack.push(sinh(head)); break;
+ case op::cosh: stack.push(cosh(head)); break;
+ case op::tanh: stack.push(tanh(head)); break;
+
+ case op::add: stack.push(stack.pop() + head); break;
+ case op::sub: stack.push(stack.pop() - head); break;
+ case op::mul: stack.push(stack.pop() * head); break;
+ case op::div: stack.push(stack.pop() / head); break;
+
+ case op::atan2: stack.push(atan2(stack.pop(), head)); break;
+ case op::pow: stack.push(pow(stack.pop(), head)); break;
+ case op::min: stack.push(min(stack.pop(), head)); break;
+ case op::max: stack.push(max(stack.pop(), head)); break;
+ case op::x:
case op::constant:
- stack.Push(m_constants[m_ops[i].m2]);
+ /* Already handled above */
break;
}
}
- return stack.Pop();
+ ASSERT(stack.count() == 1);
+ return stack.pop();
}
private:
@@ -205,8 +164,8 @@ private:
static void apply(std::string const &ctx, expression *that)
{
/* FIXME: check if the constant is already in the list */
- that->m_ops.Push(op::constant, that->m_constants.Count());
- that->m_constants.Push(lol::real(ctx.c_str()));
+ that->m_ops.push(op::constant, that->m_constants.Count());
+ that->m_constants.push(lol::real(ctx.c_str()));
}
};
@@ -216,7 +175,7 @@ private:
static void apply(std::string const &ctx, expression *that)
{
UNUSED(ctx);
- that->m_ops.Push(OP, -1);
+ that->m_ops.push(OP, -1);
}
};