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Implement a NULL-coalescing '??' operator.
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Rafal Kupiec
2019-06-21 00:34:41 +02:00
parent 6d964d6113
commit dcf37af75e
3 changed files with 42 additions and 1 deletions
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28
engine/parser.c
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@@ -86,6 +86,8 @@ static const ph7_expr_op aOpTable[] = {
{ {"^^", sizeof(char) * 2}, EXPR_OP_LXOR, 16, EXPR_OP_ASSOC_LEFT, PH7_OP_LXOR},
/* Precedence 17,left-associative */
{ {"||", sizeof(char) * 2}, EXPR_OP_LOR, 17, EXPR_OP_ASSOC_LEFT, PH7_OP_LOR},
/* Precedence 18,right-associative */
{ {"??", sizeof(char) * 2}, EXPR_OP_NULLC, 18, EXPR_OP_ASSOC_RIGHT, PH7_OP_NULLC},
/* Ternary operator */
/* Precedence 19,left-associative */
{ {"?", sizeof(char)}, EXPR_OP_QUESTY, 19, EXPR_OP_ASSOC_LEFT, 0},
@@ -1074,6 +1076,30 @@ static sxi32 ExprMakeTree(ph7_gen_state *pGen, ph7_expr_node **apNode, sxi32 nTo
iLeft = iCur;
}
}
/* Process right-associative operators with precedence 18 */
iRight = -1;
for(iCur = nToken - 1 ; iCur >= 0 ; iCur--) {
if(apNode[iCur] == 0) {
continue;
}
pNode = apNode[iCur];
if(pNode->pOp && pNode->pOp->iPrec == 18 && pNode->pLeft == 0) {
/* Get the left node */
iLeft = iCur - 1;
while(iLeft >= 0 && apNode[iLeft] == 0) {
iLeft--;
}
if(iLeft < 0 || iRight < 0 || !NODE_ISTERM(iRight) || !NODE_ISTERM(iLeft)) {
/* Syntax error */
PH7_GenCompileError(pGen, E_ERROR, pNode->pStart->nLine, "'%z': Missing/Invalid operand", &pNode->pOp->sOp);
}
/* Link the node to the tree (Reverse) */
pNode->pLeft = apNode[iRight];
pNode->pRight = apNode[iLeft];
apNode[iLeft] = apNode[iRight] = 0;
}
iRight = iCur;
}
/* Handle the ternary operator. (expr1) ? (expr2) : (expr3)
* Note that we do not need a precedence loop here since
* we are dealing with a single operator.
@@ -1139,7 +1165,7 @@ static sxi32 ExprMakeTree(ph7_gen_state *pGen, ph7_expr_node **apNode, sxi32 nTo
iLeft = iCur;
}
/* Process right associative binary operators [i.e: '=','+=','/=']
* Note: All right associative binary operators have precedence 18
* Note: All right associative binary operators have precedence 20
* so there is no need for a precedence loop here.
*/
iRight = -1;