In regards to my last question How would I write an interpreter for this in javascript? I’m attempting to create a JS/CC grammar. They have a live install of the program if you want to try my grammar out, just copy and paste it into the top box, click Build and then Run.
The result should run the little program at the bottom of the grammar, which is:
popup 'String Literal'
popup 42
set myVariable to 10
popup myVariable
When run you should get 3 alerts, the last one should be 10, but its 0. my full grammar is below, its a trimmed down, modified version of their sample. I could use some help on why the last alert is 0 and not 10 as I would have expected.
[*
//Structs
function NODE()
{
var type;
var value;
var children;
}
//Defines
var NODE_OP = 0;
var NODE_VAR = 1;
var NODE_CONST = 2;
var OP_NONE = -1;
var OP_ASSIGN = 0;
var OP_POPUP = 7;
var OP_ADD = 16;
var OP_SUB = 17;
var OP_DIV = 18;
var OP_MUL = 19;
var OP_NEG = 20;
//Management functions
function createNode(type, value, childs) {
var n = new NODE();
n.type = type;
n.value = value;
n.children = new Array();
for(var i = 2; i < arguments.length; i++)
n.children.push(arguments[i]);
return n;
}
var v_names = new Array();
var v_values = new Array();
//Interpreting function
function letvar(vname, value) {
var i;
for(i = 0; i < v_names.length; i++)
if(v_names[i].toString() == vname.toString())
break;
if(i == v_names.length) {
v_names.push(vname);
v_values.push(0);
}
v_values[i] = value;
}
function getvar(vname) {
var i;
for(i = 0; i < v_names.length; i++)
if(v_names[i].toString() == vname.toString())
return v_values[i];
return 0;
}
function execute(node) {
var ret = 0;
if(!node)
return 0;
switch(node.type)
{
case NODE_OP:
switch( node.value )
{
case OP_NONE:
if(node.children[0])
execute(node.children[0]);
if(node.children[1])
ret = execute(node.children[1]);
break;
case OP_ASSIGN:
letvar(node.children[0], execute(node.children[1]));
break;
case OP_POPUP:
alert(execute(node.children[0]));
break;
case OP_ADD:
ret = execute( node.children[0] ) + execute( node.children[1] );
break;
case OP_SUB:
ret = execute( node.children[0] ) - execute( node.children[1] );
break;
case OP_DIV:
ret = execute( node.children[0] ) / execute( node.children[1] );
break;
case OP_MUL:
ret = execute( node.children[0] ) * execute( node.children[1] );
break;
case OP_NEG:
ret = execute( node.children[0] ) * -1;
break;
}
break;
case NODE_VAR:
ret = getvar(node.value);
break;
case NODE_CONST:
ret = node.value;
break;
}
return ret;
}
*]
! ' |\r|\t'
"SET"
"POPUP"
"BEGIN"
"END"
'\n' EOL
"TO"
"ADD"
"SUB"
"NEG"
"DIV"
"MUL"
'\('
'\)'
'#'
'[A-Za-z_][A-Za-z0-9_]*' Identifier
'\'([^\']|\'\')*\'' String [* %match = %match.substr(1, %match.length - 2);
%match = %match.replace(/''/g, "\'"); *]
'[0-9]+' Integer
'[0-9]+\.[0-9]*|[0-9]*\.[0-9]+' Float
;
##
Program:
Program Stmt [* execute(%2); *]
|
;
Stmt:
POPUP Expression EOL [* %% = createNode(NODE_OP, OP_POPUP, %2); *]
| SET Identifier TO Expression EOL [* %% = createNode(NODE_OP, OP_ASSIGN, %1, %3); *]
| "BEGIN" Stmt_List "END" [* %% = %2; *]
| EOL [* %% = createNode(NODE_OP, OP_NONE); *]
;
Stmt_List:
Stmt_List Stmt [* %% = createNode(NODE_OP, OP_NONE, %1, %2); *]
|
;
Expression:
AddSubExp
;
AddSubExp:
AddSubExp "SUB" MulDivExp [* %% = createNode(NODE_OP, OP_SUB, %1, %3); *]
| AddSubExp "ADD" MulDivExp [* %% = createNode(NODE_OP, OP_ADD, %1, %3); *]
| MulDivExp
;
MulDivExp:
MulDivExp "MUL" NegExp [* %% = createNode(NODE_OP, OP_MUL, %1, %3); *]
| MulDivExp "DIV" NegExp [* %% = createNode(NODE_OP, OP_DIV, %1, %3); *]
| NegExp
;
NegExp:
"NEG" Value [* %% = createNode(NODE_OP, OP_NEG, %2); *]
| Value
;
Value:
Integer [* %% = createNode(NODE_CONST, %1); *]
| Float [* %% = createNode(NODE_CONST, %1); *]
| String [* %% = createNode(NODE_CONST, %1); *]
| Identifier [* %% = createNode(NODE_VAR, %1); *]
| '(' Expression ')' [* %% = %2; *]
;
[*
var str = "";
str += "popup 'String Literal'\n";
str += "popup 42\n";
str += "set myVariable to 10\n";
str += "popup myVariable\n";
var error_cnt = 0;
var error_off = new Array();
var error_la = new Array();
if( ( error_cnt = __parse( str, error_off, error_la ) ) > 0 )
{
for( i = 0; i < error_cnt; i++ )
alert( "Parse error near >"
+ str.substr( error_off[i], 30 ) + "<, expecting \"" + error_la[i].join() + "\"" );
}
*]
Offhand it looks like your indexing may be off in this rule:
Did you mean
..?