mathexpr.cc revision 11424:e07fd01651f3 
1/*
2 * Copyright (c) 2015 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder.  You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: David Guillen Fandos
38 */
39
40#include "sim/mathexpr.hh"
41
42#include <algorithm>
43#include <regex>
44#include <string>
45
46#include "base/misc.hh"
47
48MathExpr::MathExpr(std::string expr)
49 : ops(
50    std::array<OpSearch, uNeg + 1> {
51      OpSearch {true, bAdd, 0, '+', [] (double a, double b) { return a + b; } },
52      OpSearch {true, bSub, 0, '-', [] (double a, double b) { return a - b; } },
53      OpSearch {true, bMul, 1, '*', [] (double a, double b) { return a * b; } },
54      OpSearch {true, bDiv, 1, '/', [] (double a, double b) { return a / b; } },
55      OpSearch {false,uNeg, 2, '-', [] (double a, double b) { return -b; } },
56      OpSearch {true, bPow, 3, '^', [] (double a, double b) { return std::pow(a,b); } },
57    })
58{
59    // Cleanup
60    expr.erase(remove_if(expr.begin(), expr.end(), isspace), expr.end());
61
62    root = MathExpr::parse(expr);
63    panic_if(!root, "Invalid expression\n");
64}
65
66/**
67 * This function parses a string expression into an expression tree.
68 * It will look for operators in priority order to recursively build the
69 * tree, respecting parenthesization.
70 * Constants can be expressed in any format accepted by std::stod, whereas
71 * variables are essentially [A-Za-z0-9\.$\\]+
72 */
73MathExpr::Node *
74MathExpr::parse(std::string expr) {
75    if (expr.size() == 0)
76        return NULL;
77
78    // From low to high priority
79    int par = 0;
80    for (unsigned p = 0; p < MAX_PRIO; p++) {
81        for (int i = expr.size() - 1; i >= 0; i--) {
82            if (expr[i] == ')')
83                par++;
84            if (expr[i] == '(')
85                par--;
86
87            if (par < 0) return NULL;
88            if (par > 0) continue;
89
90            for (unsigned opt = 0; opt < ops.size(); opt++) {
91                if (ops[opt].priority != p) continue;
92                if (ops[opt].c == expr[i]) {
93                    // Try to parse each side
94                    Node *l = NULL;
95                    if (ops[opt].binary)
96                        l = parse(expr.substr(0, i));
97                    Node *r = parse(expr.substr(i + 1));
98                    if ((l && r) || (!ops[opt].binary && r)) {
99                        // Match!
100                        Node *n = new Node();
101                        n->op = ops[opt].op;
102                        n->l = l;
103                        n->r = r;
104                        return n;
105                    }
106                }
107            }
108        }
109    }
110
111    // Remove trivial parenthesis
112    if (expr.size() >= 2 && expr[0] == '(' && expr[expr.size() - 1] == ')')
113        return parse(expr.substr(1, expr.size() - 2));
114
115    // Match a number
116    {
117        char *sptr;
118        double v = strtod(expr.c_str(), &sptr);
119        if (sptr != expr.c_str()) {
120            Node *n = new Node();
121            n->op = sValue;
122            n->value = v;
123            return n;
124        }
125    }
126
127    // Match a variable
128    {
129        bool contains_non_alpha = false;
130        for (auto & c: expr)
131            contains_non_alpha = contains_non_alpha or
132                !( (c >= 'a' && c <= 'z') ||
133                   (c >= 'A' && c <= 'Z') ||
134                   (c >= '0' && c <= '9') ||
135                   c == '$' || c == '\\' || c == '.' || c == '_');
136
137        if (!contains_non_alpha) {
138            Node * n = new Node();
139            n->op = sVariable;
140            n->variable = expr;
141            return n;
142        }
143    }
144
145    return NULL;
146}
147
148double
149MathExpr::eval(const Node *n, EvalCallback fn) const {
150    if (!n)
151        return 0;
152    else if (n->op == sValue)
153        return n->value;
154    else if (n->op == sVariable)
155        return fn(n->variable);
156
157    for (auto & opt : ops)
158        if (opt.op == n->op)
159            return opt.fn( eval(n->l, fn), eval(n->r, fn) );
160
161    panic("Invalid node!\n");
162    return 0;
163}
164
165std::string
166MathExpr::toStr(Node *n, std::string prefix) const {
167    std::string ret;
168    ret += prefix + "|-- " + n->toStr() + "\n";
169    if (n->r)
170        ret += toStr(n->r, prefix + "|   ");
171    if (n->l)
172        ret += toStr(n->l, prefix + "|   ");
173    return ret;
174}
175
176