mathexpr.cc revision 12334:e0ab29a34764 
1/*
2 * Copyright (c) 2016 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 <cmath>
44#include <regex>
45#include <string>
46
47#include "base/logging.hh"
48
49MathExpr::MathExpr(std::string expr)
50 : ops(
51     std::array<OpSearch, uNeg + 1> {{
52      OpSearch {true, bAdd, 0, '+', [](double a, double b) { return a + b; }},
53      OpSearch {true, bSub, 0, '-', [](double a, double b) { return a - b; }},
54      OpSearch {true, bMul, 1, '*', [](double a, double b) { return a * b; }},
55      OpSearch {true, bDiv, 1, '/', [](double a, double b) { return a / b; }},
56      OpSearch {false,uNeg, 2, '-', [](double a, double b) { return -b; }},
57      OpSearch {true, bPow, 3, '^', [](double a, double b) {
58                 return std::pow(a,b); }
59      }},
60    })
61{
62    // Cleanup
63    expr.erase(remove_if(expr.begin(), expr.end(), isspace), expr.end());
64
65    root = MathExpr::parse(expr);
66    panic_if(!root, "Invalid expression\n");
67}
68
69/**
70 * This function parses a string expression into an expression tree.
71 * It will look for operators in priority order to recursively build the
72 * tree, respecting parenthesization.
73 * Constants can be expressed in any format accepted by std::stod, whereas
74 * variables are essentially [A-Za-z0-9\.$\\]+
75 */
76MathExpr::Node *
77MathExpr::parse(std::string expr) {
78    if (expr.size() == 0)
79        return NULL;
80
81    // From low to high priority
82    int par = 0;
83    for (unsigned p = 0; p < MAX_PRIO; p++) {
84        for (int i = expr.size() - 1; i >= 0; i--) {
85            if (expr[i] == ')')
86                par++;
87            if (expr[i] == '(')
88                par--;
89
90            if (par < 0) return NULL;
91            if (par > 0) continue;
92
93            for (unsigned opt = 0; opt < ops.size(); opt++) {
94                if (ops[opt].priority != p) continue;
95                if (ops[opt].c == expr[i]) {
96                    // Try to parse each side
97                    Node *l = NULL;
98                    if (ops[opt].binary)
99                        l = parse(expr.substr(0, i));
100                    Node *r = parse(expr.substr(i + 1));
101                    if ((l && r) || (!ops[opt].binary && r)) {
102                        // Match!
103                        Node *n = new Node();
104                        n->op = ops[opt].op;
105                        n->l = l;
106                        n->r = r;
107                        return n;
108                    }
109                }
110            }
111        }
112    }
113
114    // Remove trivial parenthesis
115    if (expr.size() >= 2 && expr[0] == '(' && expr[expr.size() - 1] == ')')
116        return parse(expr.substr(1, expr.size() - 2));
117
118    // Match a number
119    {
120        char *sptr;
121        double v = strtod(expr.c_str(), &sptr);
122        if (sptr != expr.c_str()) {
123            Node *n = new Node();
124            n->op = sValue;
125            n->value = v;
126            return n;
127        }
128    }
129
130    // Match a variable
131    {
132        bool contains_non_alpha = false;
133        for (auto & c: expr)
134            contains_non_alpha = contains_non_alpha or
135                !( (c >= 'a' && c <= 'z') ||
136                   (c >= 'A' && c <= 'Z') ||
137                   (c >= '0' && c <= '9') ||
138                   c == '$' || c == '\\' || c == '.' || c == '_');
139
140        if (!contains_non_alpha) {
141            Node * n = new Node();
142            n->op = sVariable;
143            n->variable = expr;
144            return n;
145        }
146    }
147
148    return NULL;
149}
150
151double
152MathExpr::eval(const Node *n, EvalCallback fn) const {
153    if (!n)
154        return 0;
155    else if (n->op == sValue)
156        return n->value;
157    else if (n->op == sVariable)
158        return fn(n->variable);
159
160    for (auto & opt : ops)
161        if (opt.op == n->op)
162            return opt.fn( eval(n->l, fn), eval(n->r, fn) );
163
164    panic("Invalid node!\n");
165    return 0;
166}
167
168std::string
169MathExpr::toStr(Node *n, std::string prefix) const {
170    std::string ret;
171    ret += prefix + "|-- " + n->toStr() + "\n";
172    if (n->r)
173        ret += toStr(n->r, prefix + "|   ");
174    if (n->l)
175        ret += toStr(n->l, prefix + "|   ");
176    return ret;
177}
178
179