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Stack handling for new expression evaluator

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git-svn-id: http://picoc.googlecode.com/svn/trunk@200 21eae674-98b7-11dd-bd71-f92a316d2d60
This commit is contained in:
zik.saleeba 2009-03-12 02:21:12 +00:00
parent 48a6472c68
commit 36e58ab475
1 changed files with 40 additions and 3 deletions
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43
expression.c
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@ -1,5 +1,10 @@
#include "picoc.h"
/* whether evaluation is left to right for a given precedence level */
#define IS_LEFT_TO_RIGHT(p) ((p) != 2 && (p) != 3 && (p) != 14)
/* local prototypes */
void ExpressionParseFunctionCall(struct ParseState *Parser, struct Value **Result, const char *FuncName);
@ -396,6 +401,24 @@ int ExpressionParse(struct ParseState *Parser, struct Value **Result)
}
#else
enum OperatorOrder
{
OrderPrefix,
OrderInfix,
OrderPostfix
};
/* a stack of expressions we use in evaluation */
struct ExpressionStack
{
struct ExprStack *Next; /* the next lower item on the stack */
struct Value *Val; /* the value for this stack node */
enum EvaluationOrder Order; /* the evaluation order of this operator */
enum LexToken Op; /* the operator */
short Precedence; /* the operator precedence of this node */
short LeftToRight; /* indicates left to right evaluation, otherwise right to left */
};
/* operator precedence definitions */
struct OpPrecedence
{
@ -433,13 +456,25 @@ void ExpressionStackCollapse(struct ParseState *Parser, struct ExpressionStack *
}
/* push an operator on to the expression stack */
void ExpressionStackPushOperator(struct ParseState *Parser, struct ExpressionStack **StackTop, enum OperatorOrder Order, enum LexToken Token, int Precedence)
void ExpressionStackPushOperator(struct ParseState *Parser, struct ExpressionStack **StackTop, enum OperatorOrder Order, enum LexToken Token, int Precedence, int LeftToRight)
{
struct ExpressionStack *StackNode = VariableAlloc(Parser, sizeof(struct ExpressionStack), FALSE);
StackNode->Next = *StackTop;
StackNode->Order = Order;
StackNode->Op = Token;
StackNode->Precedence = Precedence;
StackNode->LeftToRight = LeftToRight;
*StackTop = StackNode;
}
/* push a value on to the expression stack */
void ExpressionStackPushValue(struct ParseState *Parser, struct ExpressionStack **StackTop, struct Value *PushValue)
{
struct Value *ValueLoc = VariableAllocValueAndCopy(Parser, PushValue, FALSE);
struct ExpressionStack *StackNode = VariableAlloc(Parser, sizeof(struct ExpressionStack), FALSE);
StackNode->Next = *StackTop;
StackNode->Val = ValueLoc;
*StackTop = StackNode;
}
/* parse an expression with operator precedence */
@ -449,6 +484,7 @@ int ExpressionParse(struct ParseState *Parser, struct Value **Result)
bool PrefixState = false;
bool Done = false;
int BracketPrecedence = 0;
int LocalPrecedence;
int Precedence = 0;
struct ExpressionStack *StackTop = NULL;
@ -464,11 +500,12 @@ int ExpressionParse(struct ParseState *Parser, struct Value **Result)
if (Parser->Mode == RunModeRun)
{
Precedence = BracketPrecedence + OperatorPrecedence[(int)Token].PrefixPrecedence;
LocalPrecedence = OperatorPrecedence[(int)Token].PrefixPrecedence;
Precedence = BracketPrecedence + LocalPrecedence;
if (Token == TokenOpenBracket || Token == TokenLeftSquareBracket)
{ /* boost the bracket operator precedence, then push */
BracketPrecedence += BRACKET_PREDECENCE;
ExpressionStackPushOperator(Parser, &StackTop, OrderPrefix, Token, Precedence);
ExpressionStackPushOperator(Parser, &StackTop, OrderPrefix, Token, Precedence, IS_LEFT_TO_RIGHT(LocalPrecedence));
}
else
{ /* scan and collapse the stack to the precedence of this operator, then push */