mathexpr.cc revision 11527:9007a9729815 
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 <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) {
57                 return std::pow(a,b); }
58      },
59    })
60{
61    // Cleanup
62    expr.erase(remove_if(expr.begin(), expr.end(), isspace), expr.end());
63
64    root = MathExpr::parse(expr);
65    panic_if(!root, "Invalid expression\n");
66}
67
68/**
69 * This function parses a string expression into an expression tree.
70 * It will look for operators in priority order to recursively build the
71 * tree, respecting parenthesization.
72 * Constants can be expressed in any format accepted by std::stod, whereas
73 * variables are essentially [A-Za-z0-9\.$\\]+
74 */
75MathExpr::Node *
76MathExpr::parse(std::string expr) {
77    if (expr.size() == 0)
78        return NULL;
79
80    // From low to high priority
81    int par = 0;
82    for (unsigned p = 0; p < MAX_PRIO; p++) {
83        for (int i = expr.size() - 1; i >= 0; i--) {
84            if (expr[i] == ')')
85                par++;
86            if (expr[i] == '(')
87                par--;
88
89            if (par < 0) return NULL;
90            if (par > 0) continue;
91
92            for (unsigned opt = 0; opt < ops.size(); opt++) {
93                if (ops[opt].priority != p) continue;
94                if (ops[opt].c == expr[i]) {
95                    // Try to parse each side
96                    Node *l = NULL;
97                    if (ops[opt].binary)
98                        l = parse(expr.substr(0, i));
99                    Node *r = parse(expr.substr(i + 1));
100                    if ((l && r) || (!ops[opt].binary && r)) {
101                        // Match!
102                        Node *n = new Node();
103                        n->op = ops[opt].op;
104                        n->l = l;
105                        n->r = r;
106                        return n;
107                    }
108                }
109            }
110        }
111    }
112
113    // Remove trivial parenthesis
114    if (expr.size() >= 2 && expr[0] == '(' && expr[expr.size() - 1] == ')')
115        return parse(expr.substr(1, expr.size() - 2));
116
117    // Match a number
118    {
119        char *sptr;
120        double v = strtod(expr.c_str(), &sptr);
121        if (sptr != expr.c_str()) {
122            Node *n = new Node();
123            n->op = sValue;
124            n->value = v;
125            return n;
126        }
127    }
128
129    // Match a variable
130    {
131        bool contains_non_alpha = false;
132        for (auto & c: expr)
133            contains_non_alpha = contains_non_alpha or
134                !( (c >= 'a' && c <= 'z') ||
135                   (c >= 'A' && c <= 'Z') ||
136                   (c >= '0' && c <= '9') ||
137                   c == '$' || c == '\\' || c == '.' || c == '_');
138
139        if (!contains_non_alpha) {
140            Node * n = new Node();
141            n->op = sVariable;
142            n->variable = expr;
143            return n;
144        }
145    }
146
147    return NULL;
148}
149
150double
151MathExpr::eval(const Node *n, EvalCallback fn) const {
152    if (!n)
153        return 0;
154    else if (n->op == sValue)
155        return n->value;
156    else if (n->op == sVariable)
157        return fn(n->variable);
158
159    for (auto & opt : ops)
160        if (opt.op == n->op)
161            return opt.fn( eval(n->l, fn), eval(n->r, fn) );
162
163    panic("Invalid node!\n");
164    return 0;
165}
166
167std::string
168MathExpr::toStr(Node *n, std::string prefix) const {
169    std::string ret;
170    ret += prefix + "|-- " + n->toStr() + "\n";
171    if (n->r)
172        ret += toStr(n->r, prefix + "|   ");
173    if (n->l)
174        ret += toStr(n->l, prefix + "|   ");
175    return ret;
176}
177
178