split math code out of ash and into a standalone library so we can use it in any shell (like hush!)

2009-04-02 10:02:37 +00:00 · 2009-04-02 10:02:37 +00:00 · 98c52645c0
commit 98c52645c0
parent 551ffdccea
6 changed files with 945 additions and 726 deletions
--- a/shell/math.c
+++ b/shell/math.c
@ -0,0 +1,701 @@
+/*
+ * arithmetic code ripped out of ash shell for code sharing
+ *
+ * Copyright (c) 1989, 1991, 1993, 1994
+ *      The Regents of the University of California.  All rights reserved.
+ *
+ * Copyright (c) 1997-2005 Herbert Xu <herbert@gondor.apana.org.au>
+ * was re-ported from NetBSD and debianized.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Kenneth Almquist.
+ *
+ * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ *
+ * Original BSD copyright notice is retained at the end of this file.
+ */
+/*
+ * rewrite arith.y to micro stack based cryptic algorithm by
+ * Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
+ *
+ * Modified by Paul Mundt <lethal@linux-sh.org> (c) 2004 to support
+ * dynamic variables.
+ *
+ * Modified by Vladimir Oleynik <dzo@simtreas.ru> (c) 2001-2005 to be
+ * used in busybox and size optimizations,
+ * rewrote arith (see notes to this), added locale support,
+ * rewrote dynamic variables.
+ */
+
+#include "busybox.h"
+#include "math.h"
+
+#define a_e_h_t arith_eval_hooks_t
+#define lookupvar (math_hooks->lookupvar)
+#define setvar (math_hooks->setvar)
+#define endofname (math_hooks->endofname)
+
+/* Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
+
+   Permission is hereby granted, free of charge, to any person obtaining
+   a copy of this software and associated documentation files (the
+   "Software"), to deal in the Software without restriction, including
+   without limitation the rights to use, copy, modify, merge, publish,
+   distribute, sublicense, and/or sell copies of the Software, and to
+   permit persons to whom the Software is furnished to do so, subject to
+   the following conditions:
+
+   The above copyright notice and this permission notice shall be
+   included in all copies or substantial portions of the Software.
+
+   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+   EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+   MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+   IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+   CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+   TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+   SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+*/
+
+/* This is my infix parser/evaluator. It is optimized for size, intended
+ * as a replacement for yacc-based parsers. However, it may well be faster
+ * than a comparable parser written in yacc. The supported operators are
+ * listed in #defines below. Parens, order of operations, and error handling
+ * are supported. This code is thread safe. The exact expression format should
+ * be that which POSIX specifies for shells. */
+
+/* The code uses a simple two-stack algorithm. See
+ * http://www.onthenet.com.au/~grahamis/int2008/week02/lect02.html
+ * for a detailed explanation of the infix-to-postfix algorithm on which
+ * this is based (this code differs in that it applies operators immediately
+ * to the stack instead of adding them to a queue to end up with an
+ * expression). */
+
+/* To use the routine, call it with an expression string and error return
+ * pointer */
+
+/*
+ * Aug 24, 2001              Manuel Novoa III
+ *
+ * Reduced the generated code size by about 30% (i386) and fixed several bugs.
+ *
+ * 1) In arith_apply():
+ *    a) Cached values of *numptr and &(numptr[-1]).
+ *    b) Removed redundant test for zero denominator.
+ *
+ * 2) In arith():
+ *    a) Eliminated redundant code for processing operator tokens by moving
+ *       to a table-based implementation.  Also folded handling of parens
+ *       into the table.
+ *    b) Combined all 3 loops which called arith_apply to reduce generated
+ *       code size at the cost of speed.
+ *
+ * 3) The following expressions were treated as valid by the original code:
+ *       1()  ,    0!  ,    1 ( *3 )   .
+ *    These bugs have been fixed by internally enclosing the expression in
+ *    parens and then checking that all binary ops and right parens are
+ *    preceded by a valid expression (NUM_TOKEN).
+ *
+ * Note: It may be desirable to replace Aaron's test for whitespace with
+ * ctype's isspace() if it is used by another busybox applet or if additional
+ * whitespace chars should be considered.  Look below the "#include"s for a
+ * precompiler test.
+ */
+
+/*
+ * Aug 26, 2001              Manuel Novoa III
+ *
+ * Return 0 for null expressions.  Pointed out by Vladimir Oleynik.
+ *
+ * Merge in Aaron's comments previously posted to the busybox list,
+ * modified slightly to take account of my changes to the code.
+ *
+ */
+
+/*
+ *  (C) 2003 Vladimir Oleynik <dzo@simtreas.ru>
+ *
+ * - allow access to variable,
+ *   used recursive find value indirection (c=2*2; a="c"; $((a+=2)) produce 6)
+ * - realize assign syntax (VAR=expr, +=, *= etc)
+ * - realize exponentiation (** operator)
+ * - realize comma separated - expr, expr
+ * - realise ++expr --expr expr++ expr--
+ * - realise expr ? expr : expr (but, second expr calculate always)
+ * - allow hexadecimal and octal numbers
+ * - was restored loses XOR operator
+ * - remove one goto label, added three ;-)
+ * - protect $((num num)) as true zero expr (Manuel`s error)
+ * - always use special isspace(), see comment from bash ;-)
+ */
+
+#define arith_isspace(arithval) \
+	(arithval == ' ' || arithval == '\n' || arithval == '\t')
+
+typedef unsigned char operator;
+
+/* An operator's token id is a bit of a bitfield. The lower 5 bits are the
+ * precedence, and 3 high bits are an ID unique across operators of that
+ * precedence. The ID portion is so that multiple operators can have the
+ * same precedence, ensuring that the leftmost one is evaluated first.
+ * Consider * and /. */
+
+#define tok_decl(prec,id) (((id)<<5)|(prec))
+#define PREC(op) ((op) & 0x1F)
+
+#define TOK_LPAREN tok_decl(0,0)
+
+#define TOK_COMMA tok_decl(1,0)
+
+#define TOK_ASSIGN tok_decl(2,0)
+#define TOK_AND_ASSIGN tok_decl(2,1)
+#define TOK_OR_ASSIGN tok_decl(2,2)
+#define TOK_XOR_ASSIGN tok_decl(2,3)
+#define TOK_PLUS_ASSIGN tok_decl(2,4)
+#define TOK_MINUS_ASSIGN tok_decl(2,5)
+#define TOK_LSHIFT_ASSIGN tok_decl(2,6)
+#define TOK_RSHIFT_ASSIGN tok_decl(2,7)
+
+#define TOK_MUL_ASSIGN tok_decl(3,0)
+#define TOK_DIV_ASSIGN tok_decl(3,1)
+#define TOK_REM_ASSIGN tok_decl(3,2)
+
+/* all assign is right associativity and precedence eq, but (7+3)<<5 > 256 */
+#define convert_prec_is_assing(prec) do { if (prec == 3) prec = 2; } while (0)
+
+/* conditional is right associativity too */
+#define TOK_CONDITIONAL tok_decl(4,0)
+#define TOK_CONDITIONAL_SEP tok_decl(4,1)
+
+#define TOK_OR tok_decl(5,0)
+
+#define TOK_AND tok_decl(6,0)
+
+#define TOK_BOR tok_decl(7,0)
+
+#define TOK_BXOR tok_decl(8,0)
+
+#define TOK_BAND tok_decl(9,0)
+
+#define TOK_EQ tok_decl(10,0)
+#define TOK_NE tok_decl(10,1)
+
+#define TOK_LT tok_decl(11,0)
+#define TOK_GT tok_decl(11,1)
+#define TOK_GE tok_decl(11,2)
+#define TOK_LE tok_decl(11,3)
+
+#define TOK_LSHIFT tok_decl(12,0)
+#define TOK_RSHIFT tok_decl(12,1)
+
+#define TOK_ADD tok_decl(13,0)
+#define TOK_SUB tok_decl(13,1)
+
+#define TOK_MUL tok_decl(14,0)
+#define TOK_DIV tok_decl(14,1)
+#define TOK_REM tok_decl(14,2)
+
+/* exponent is right associativity */
+#define TOK_EXPONENT tok_decl(15,1)
+
+/* For now unary operators. */
+#define UNARYPREC 16
+#define TOK_BNOT tok_decl(UNARYPREC,0)
+#define TOK_NOT tok_decl(UNARYPREC,1)
+
+#define TOK_UMINUS tok_decl(UNARYPREC+1,0)
+#define TOK_UPLUS tok_decl(UNARYPREC+1,1)
+
+#define PREC_PRE (UNARYPREC+2)
+
+#define TOK_PRE_INC tok_decl(PREC_PRE, 0)
+#define TOK_PRE_DEC tok_decl(PREC_PRE, 1)
+
+#define PREC_POST (UNARYPREC+3)
+
+#define TOK_POST_INC tok_decl(PREC_POST, 0)
+#define TOK_POST_DEC tok_decl(PREC_POST, 1)
+
+#define SPEC_PREC (UNARYPREC+4)
+
+#define TOK_NUM tok_decl(SPEC_PREC, 0)
+#define TOK_RPAREN tok_decl(SPEC_PREC, 1)
+
+#define NUMPTR (*numstackptr)
+
+static int
+tok_have_assign(operator op)
+{
+	operator prec = PREC(op);
+
+	convert_prec_is_assing(prec);
+	return (prec == PREC(TOK_ASSIGN) ||
+			prec == PREC_PRE || prec == PREC_POST);
+}
+
+static int
+is_right_associativity(operator prec)
+{
+	return (prec == PREC(TOK_ASSIGN) || prec == PREC(TOK_EXPONENT)
+	        || prec == PREC(TOK_CONDITIONAL));
+}
+
+typedef struct {
+	arith_t val;
+	arith_t contidional_second_val;
+	char contidional_second_val_initialized;
+	char *var;      /* if NULL then is regular number,
+			   else is variable name */
+} v_n_t;
+
+typedef struct chk_var_recursive_looped_t {
+	const char *var;
+	struct chk_var_recursive_looped_t *next;
+} chk_var_recursive_looped_t;
+
+static chk_var_recursive_looped_t *prev_chk_var_recursive;
+
+static int
+arith_lookup_val(v_n_t *t, a_e_h_t *math_hooks)
+{
+	if (t->var) {
+		const char * p = lookupvar(t->var);
+
+		if (p) {
+			int errcode;
+
+			/* recursive try as expression */
+			chk_var_recursive_looped_t *cur;
+			chk_var_recursive_looped_t cur_save;
+
+			for (cur = prev_chk_var_recursive; cur; cur = cur->next) {
+				if (strcmp(cur->var, t->var) == 0) {
+					/* expression recursion loop detected */
+					return -5;
+				}
+			}
+			/* save current lookuped var name */
+			cur = prev_chk_var_recursive;
+			cur_save.var = t->var;
+			cur_save.next = cur;
+			prev_chk_var_recursive = &cur_save;
+
+			t->val = arith (p, &errcode, math_hooks);
+			/* restore previous ptr after recursiving */
+			prev_chk_var_recursive = cur;
+			return errcode;
+		}
+		/* allow undefined var as 0 */
+		t->val = 0;
+	}
+	return 0;
+}
+
+/* "applying" a token means performing it on the top elements on the integer
+ * stack. For a unary operator it will only change the top element, but a
+ * binary operator will pop two arguments and push a result */
+static int
+arith_apply(operator op, v_n_t *numstack, v_n_t **numstackptr, a_e_h_t *math_hooks)
+{
+	v_n_t *numptr_m1;
+	arith_t numptr_val, rez;
+	int ret_arith_lookup_val;
+
+	/* There is no operator that can work without arguments */
+	if (NUMPTR == numstack) goto err;
+	numptr_m1 = NUMPTR - 1;
+
+	/* check operand is var with noninteger value */
+	ret_arith_lookup_val = arith_lookup_val(numptr_m1, math_hooks);
+	if (ret_arith_lookup_val)
+		return ret_arith_lookup_val;
+
+	rez = numptr_m1->val;
+	if (op == TOK_UMINUS)
+		rez *= -1;
+	else if (op == TOK_NOT)
+		rez = !rez;
+	else if (op == TOK_BNOT)
+		rez = ~rez;
+	else if (op == TOK_POST_INC || op == TOK_PRE_INC)
+		rez++;
+	else if (op == TOK_POST_DEC || op == TOK_PRE_DEC)
+		rez--;
+	else if (op != TOK_UPLUS) {
+		/* Binary operators */
+
+		/* check and binary operators need two arguments */
+		if (numptr_m1 == numstack) goto err;
+
+		/* ... and they pop one */
+		--NUMPTR;
+		numptr_val = rez;
+		if (op == TOK_CONDITIONAL) {
+			if (!numptr_m1->contidional_second_val_initialized) {
+				/* protect $((expr1 ? expr2)) without ": expr" */
+				goto err;
+			}
+			rez = numptr_m1->contidional_second_val;
+		} else if (numptr_m1->contidional_second_val_initialized) {
+			/* protect $((expr1 : expr2)) without "expr ? " */
+			goto err;
+		}
+		numptr_m1 = NUMPTR - 1;
+		if (op != TOK_ASSIGN) {
+			/* check operand is var with noninteger value for not '=' */
+			ret_arith_lookup_val = arith_lookup_val(numptr_m1, math_hooks);
+			if (ret_arith_lookup_val)
+				return ret_arith_lookup_val;
+		}
+		if (op == TOK_CONDITIONAL) {
+			numptr_m1->contidional_second_val = rez;
+		}
+		rez = numptr_m1->val;
+		if (op == TOK_BOR || op == TOK_OR_ASSIGN)
+			rez |= numptr_val;
+		else if (op == TOK_OR)
+			rez = numptr_val || rez;
+		else if (op == TOK_BAND || op == TOK_AND_ASSIGN)
+			rez &= numptr_val;
+		else if (op == TOK_BXOR || op == TOK_XOR_ASSIGN)
+			rez ^= numptr_val;
+		else if (op == TOK_AND)
+			rez = rez && numptr_val;
+		else if (op == TOK_EQ)
+			rez = (rez == numptr_val);
+		else if (op == TOK_NE)
+			rez = (rez != numptr_val);
+		else if (op == TOK_GE)
+			rez = (rez >= numptr_val);
+		else if (op == TOK_RSHIFT || op == TOK_RSHIFT_ASSIGN)
+			rez >>= numptr_val;
+		else if (op == TOK_LSHIFT || op == TOK_LSHIFT_ASSIGN)
+			rez <<= numptr_val;
+		else if (op == TOK_GT)
+			rez = (rez > numptr_val);
+		else if (op == TOK_LT)
+			rez = (rez < numptr_val);
+		else if (op == TOK_LE)
+			rez = (rez <= numptr_val);
+		else if (op == TOK_MUL || op == TOK_MUL_ASSIGN)
+			rez *= numptr_val;
+		else if (op == TOK_ADD || op == TOK_PLUS_ASSIGN)
+			rez += numptr_val;
+		else if (op == TOK_SUB || op == TOK_MINUS_ASSIGN)
+			rez -= numptr_val;
+		else if (op == TOK_ASSIGN || op == TOK_COMMA)
+			rez = numptr_val;
+		else if (op == TOK_CONDITIONAL_SEP) {
+			if (numptr_m1 == numstack) {
+				/* protect $((expr : expr)) without "expr ? " */
+				goto err;
+			}
+			numptr_m1->contidional_second_val_initialized = op;
+			numptr_m1->contidional_second_val = numptr_val;
+		} else if (op == TOK_CONDITIONAL) {
+			rez = rez ?
+				numptr_val : numptr_m1->contidional_second_val;
+		} else if (op == TOK_EXPONENT) {
+			if (numptr_val < 0)
+				return -3;      /* exponent less than 0 */
+			else {
+				arith_t c = 1;
+
+				if (numptr_val)
+					while (numptr_val--)
+						c *= rez;
+				rez = c;
+			}
+		} else if (numptr_val==0)          /* zero divisor check */
+			return -2;
+		else if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
+			rez /= numptr_val;
+		else if (op == TOK_REM || op == TOK_REM_ASSIGN)
+			rez %= numptr_val;
+	}
+	if (tok_have_assign(op)) {
+		char buf[sizeof(arith_t_type)*3 + 2];
+
+		if (numptr_m1->var == NULL) {
+			/* Hmm, 1=2 ? */
+			goto err;
+		}
+		/* save to shell variable */
+		snprintf(buf, sizeof(buf), arith_t_fmt, (arith_t_type) rez);
+		setvar(numptr_m1->var, buf, 0);
+		/* after saving, make previous value for v++ or v-- */
+		if (op == TOK_POST_INC)
+			rez--;
+		else if (op == TOK_POST_DEC)
+			rez++;
+	}
+	numptr_m1->val = rez;
+	/* protect geting var value, is number now */
+	numptr_m1->var = NULL;
+	return 0;
+ err:
+	return -1;
+}
+
+/* longest must be first */
+static const char op_tokens[] ALIGN1 = {
+	'<','<','=',0, TOK_LSHIFT_ASSIGN,
+	'>','>','=',0, TOK_RSHIFT_ASSIGN,
+	'<','<',    0, TOK_LSHIFT,
+	'>','>',    0, TOK_RSHIFT,
+	'|','|',    0, TOK_OR,
+	'&','&',    0, TOK_AND,
+	'!','=',    0, TOK_NE,
+	'<','=',    0, TOK_LE,
+	'>','=',    0, TOK_GE,
+	'=','=',    0, TOK_EQ,
+	'|','=',    0, TOK_OR_ASSIGN,
+	'&','=',    0, TOK_AND_ASSIGN,
+	'*','=',    0, TOK_MUL_ASSIGN,
+	'/','=',    0, TOK_DIV_ASSIGN,
+	'%','=',    0, TOK_REM_ASSIGN,
+	'+','=',    0, TOK_PLUS_ASSIGN,
+	'-','=',    0, TOK_MINUS_ASSIGN,
+	'-','-',    0, TOK_POST_DEC,
+	'^','=',    0, TOK_XOR_ASSIGN,
+	'+','+',    0, TOK_POST_INC,
+	'*','*',    0, TOK_EXPONENT,
+	'!',        0, TOK_NOT,
+	'<',        0, TOK_LT,
+	'>',        0, TOK_GT,
+	'=',        0, TOK_ASSIGN,
+	'|',        0, TOK_BOR,
+	'&',        0, TOK_BAND,
+	'*',        0, TOK_MUL,
+	'/',        0, TOK_DIV,
+	'%',        0, TOK_REM,
+	'+',        0, TOK_ADD,
+	'-',        0, TOK_SUB,
+	'^',        0, TOK_BXOR,
+	/* uniq */
+	'~',        0, TOK_BNOT,
+	',',        0, TOK_COMMA,
+	'?',        0, TOK_CONDITIONAL,
+	':',        0, TOK_CONDITIONAL_SEP,
+	')',        0, TOK_RPAREN,
+	'(',        0, TOK_LPAREN,
+	0
+};
+/* ptr to ")" */
+#define endexpression (&op_tokens[sizeof(op_tokens)-7])
+
+arith_t
+arith(const char *expr, int *perrcode, a_e_h_t *math_hooks)
+{
+	char arithval; /* Current character under analysis */
+	operator lasttok, op;
+	operator prec;
+	operator *stack, *stackptr;
+	const char *p = endexpression;
+	int errcode;
+	v_n_t *numstack, *numstackptr;
+	unsigned datasizes = strlen(expr) + 2;
+
+	/* Stack of integers */
+	/* The proof that there can be no more than strlen(startbuf)/2+1 integers
+	 * in any given correct or incorrect expression is left as an exercise to
+	 * the reader. */
+	numstackptr = numstack = alloca((datasizes / 2) * sizeof(numstack[0]));
+	/* Stack of operator tokens */
+	stackptr = stack = alloca(datasizes * sizeof(stack[0]));
+
+	*stackptr++ = lasttok = TOK_LPAREN;     /* start off with a left paren */
+	*perrcode = errcode = 0;
+
+	while (1) {
+		arithval = *expr;
+		if (arithval == 0) {
+			if (p == endexpression) {
+				/* Null expression. */
+				return 0;
+			}
+
+			/* This is only reached after all tokens have been extracted from the
+			 * input stream. If there are still tokens on the operator stack, they
+			 * are to be applied in order. At the end, there should be a final
+			 * result on the integer stack */
+
+			if (expr != endexpression + 1) {
+				/* If we haven't done so already, */
+				/* append a closing right paren */
+				expr = endexpression;
+				/* and let the loop process it. */
+				continue;
+			}
+			/* At this point, we're done with the expression. */
+			if (numstackptr != numstack+1) {
+				/* ... but if there isn't, it's bad */
+ err:
+				*perrcode = -1;
+				return *perrcode;
+			}
+			if (numstack->var) {
+				/* expression is $((var)) only, lookup now */
+				errcode = arith_lookup_val(numstack, math_hooks);
+			}
+ ret:
+			*perrcode = errcode;
+			return numstack->val;
+		}
+
+		/* Continue processing the expression. */
+		if (arith_isspace(arithval)) {
+			/* Skip whitespace */
+			goto prologue;
+		}
+		p = endofname(expr);
+		if (p != expr) {
+			size_t var_name_size = (p-expr) + 1;  /* trailing zero */
+
+			numstackptr->var = alloca(var_name_size);
+			safe_strncpy(numstackptr->var, expr, var_name_size);
+			expr = p;
+ num:
+			numstackptr->contidional_second_val_initialized = 0;
+			numstackptr++;
+			lasttok = TOK_NUM;
+			continue;
+		}
+		if (isdigit(arithval)) {
+			numstackptr->var = NULL;
+			numstackptr->val = strto_arith_t(expr, (char **) &expr, 0);
+			goto num;
+		}
+		for (p = op_tokens; ; p++) {
+			const char *o;
+
+			if (*p == 0) {
+				/* strange operator not found */
+				goto err;
+			}
+			for (o = expr; *p && *o == *p; p++)
+				o++;
+			if (!*p) {
+				/* found */
+				expr = o - 1;
+				break;
+			}
+			/* skip tail uncompared token */
+			while (*p)
+				p++;
+			/* skip zero delim */
+			p++;
+		}
+		op = p[1];
+
+		/* post grammar: a++ reduce to num */
+		if (lasttok == TOK_POST_INC || lasttok == TOK_POST_DEC)
+			lasttok = TOK_NUM;
+
+		/* Plus and minus are binary (not unary) _only_ if the last
+		 * token was as number, or a right paren (which pretends to be
+		 * a number, since it evaluates to one). Think about it.
+		 * It makes sense. */
+		if (lasttok != TOK_NUM) {
+			switch (op) {
+			case TOK_ADD:
+				op = TOK_UPLUS;
+				break;
+			case TOK_SUB:
+				op = TOK_UMINUS;
+				break;
+			case TOK_POST_INC:
+				op = TOK_PRE_INC;
+				break;
+			case TOK_POST_DEC:
+				op = TOK_PRE_DEC;
+				break;
+			}
+		}
+		/* We don't want a unary operator to cause recursive descent on the
+		 * stack, because there can be many in a row and it could cause an
+		 * operator to be evaluated before its argument is pushed onto the
+		 * integer stack. */
+		/* But for binary operators, "apply" everything on the operator
+		 * stack until we find an operator with a lesser priority than the
+		 * one we have just extracted. */
+		/* Left paren is given the lowest priority so it will never be
+		 * "applied" in this way.
+		 * if associativity is right and priority eq, applied also skip
+		 */
+		prec = PREC(op);
+		if ((prec > 0 && prec < UNARYPREC) || prec == SPEC_PREC) {
+			/* not left paren or unary */
+			if (lasttok != TOK_NUM) {
+				/* binary op must be preceded by a num */
+				goto err;
+			}
+			while (stackptr != stack) {
+				if (op == TOK_RPAREN) {
+					/* The algorithm employed here is simple: while we don't
+					 * hit an open paren nor the bottom of the stack, pop
+					 * tokens and apply them */
+					if (stackptr[-1] == TOK_LPAREN) {
+						--stackptr;
+						/* Any operator directly after a */
+						lasttok = TOK_NUM;
+						/* close paren should consider itself binary */
+						goto prologue;
+					}
+				} else {
+					operator prev_prec = PREC(stackptr[-1]);
+
+					convert_prec_is_assing(prec);
+					convert_prec_is_assing(prev_prec);
+					if (prev_prec < prec)
+						break;
+					/* check right assoc */
+					if (prev_prec == prec && is_right_associativity(prec))
+						break;
+				}
+				errcode = arith_apply(*--stackptr, numstack, &numstackptr, math_hooks);
+				if (errcode) goto ret;
+			}
+			if (op == TOK_RPAREN) {
+				goto err;
+			}
+		}
+
+		/* Push this operator to the stack and remember it. */
+		*stackptr++ = lasttok = op;
+ prologue:
+		++expr;
+	} /* while */
+}
+
+/*-
+ * Copyright (c) 1989, 1991, 1993, 1994
+ *      The Regents of the University of California.  All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Kenneth Almquist.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */