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TechplexEngineer/grammar

Created July 5, 2019 13:00
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PEG Question
Raw
grammar
// Simple Arithmetics Grammar
// ==========================
//
// Accepts expressions like "2 * (3 + 4)" and computes their value.
Expression
= head:Term tail:(_ ("+" / "-") _ Term)* {
return tail.reduce(function(result, element) {
if (element[1] === "+") { return result + element[3]; }
if (element[1] === "-") { return result - element[3]; }
}, head);
}
Term
= head:Factor tail:(_ ("*" / "/") _ Factor)* {
return tail.reduce(function(result, element) {
if (element[1] === "*") { return result * element[3]; }
if (element[1] === "/") { return result / element[3]; }
}, head);
}
Factor
= "(" _ expr:Expression _ ")" { return expr; }
/ Integer
Integer "integer"
= _ [0-9]+ { return parseInt(text(), 10); }
_ "whitespace"
= [ \t\n\r]*
Raw
parser.js
module.exports = /*
* Generated by PEG.js 0.10.0.
*
* http://pegjs.org/
*/
(function() {
"use strict";
function peg$subclass(child, parent) {
function ctor() { this.constructor = child; }
ctor.prototype = parent.prototype;
child.prototype = new ctor();
}
function peg$SyntaxError(message, expected, found, location) {
this.message = message;
this.expected = expected;
this.found = found;
this.location = location;
this.name = "SyntaxError";
if (typeof Error.captureStackTrace === "function") {
Error.captureStackTrace(this, peg$SyntaxError);
}
}
peg$subclass(peg$SyntaxError, Error);
peg$SyntaxError.buildMessage = function(expected, found) {
var DESCRIBE_EXPECTATION_FNS = {
literal: function(expectation) {
return "\"" + literalEscape(expectation.text) + "\"";
},
"class": function(expectation) {
var escapedParts = "",
i;
for (i = 0; i < expectation.parts.length; i++) {
escapedParts += expectation.parts[i] instanceof Array
? classEscape(expectation.parts[i][0]) + "-" + classEscape(expectation.parts[i][1])
: classEscape(expectation.parts[i]);
}
return "[" + (expectation.inverted ? "^" : "") + escapedParts + "]";
},
any: function(expectation) {
return "any character";
},
end: function(expectation) {
return "end of input";
},
other: function(expectation) {
return expectation.description;
}
};
function hex(ch) {
return ch.charCodeAt(0).toString(16).toUpperCase();
}
function literalEscape(s) {
return s
.replace(/\\/g, '\\\\')
.replace(/"/g, '\\"')
.replace(/\0/g, '\\0')
.replace(/\t/g, '\\t')
.replace(/\n/g, '\\n')
.replace(/\r/g, '\\r')
.replace(/[\x00-\x0F]/g, function(ch) { return '\\x0' + hex(ch); })
.replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return '\\x' + hex(ch); });
}
function classEscape(s) {
return s
.replace(/\\/g, '\\\\')
.replace(/\]/g, '\\]')
.replace(/\^/g, '\\^')
.replace(/-/g, '\\-')
.replace(/\0/g, '\\0')
.replace(/\t/g, '\\t')
.replace(/\n/g, '\\n')
.replace(/\r/g, '\\r')
.replace(/[\x00-\x0F]/g, function(ch) { return '\\x0' + hex(ch); })
.replace(/[\x10-\x1F\x7F-\x9F]/g, function(ch) { return '\\x' + hex(ch); });
}
function describeExpectation(expectation) {
return DESCRIBE_EXPECTATION_FNS[expectation.type](expectation);
}
function describeExpected(expected) {
var descriptions = new Array(expected.length),
i, j;
for (i = 0; i < expected.length; i++) {
descriptions[i] = describeExpectation(expected[i]);
}
descriptions.sort();
if (descriptions.length > 0) {
for (i = 1, j = 1; i < descriptions.length; i++) {
if (descriptions[i - 1] !== descriptions[i]) {
descriptions[j] = descriptions[i];
j++;
}
}
descriptions.length = j;
}
switch (descriptions.length) {
case 1:
return descriptions[0];
case 2:
return descriptions[0] + " or " + descriptions[1];
default:
return descriptions.slice(0, -1).join(", ")
+ ", or "
+ descriptions[descriptions.length - 1];
}
}
function describeFound(found) {
return found ? "\"" + literalEscape(found) + "\"" : "end of input";
}
return "Expected " + describeExpected(expected) + " but " + describeFound(found) + " found.";
};
function peg$parse(input, options) {
options = options !== void 0 ? options : {};
var peg$FAILED = {},
peg$startRuleFunctions = { Expression: peg$parseExpression },
peg$startRuleFunction = peg$parseExpression,
peg$c0 = "+",
peg$c1 = peg$literalExpectation("+", false),
peg$c2 = "-",
peg$c3 = peg$literalExpectation("-", false),
peg$c4 = function(head, tail) {
return tail.reduce(function(result, element) {
if (element[1] === "+") { return result + element[3]; }
if (element[1] === "-") { return result - element[3]; }
}, head);
},
peg$c5 = "*",
peg$c6 = peg$literalExpectation("*", false),
peg$c7 = "/",
peg$c8 = peg$literalExpectation("/", false),
peg$c9 = function(head, tail) {
return tail.reduce(function(result, element) {
if (element[1] === "*") { return result * element[3]; }
if (element[1] === "/") { return result / element[3]; }
}, head);
},
peg$c10 = "(",
peg$c11 = peg$literalExpectation("(", false),
peg$c12 = ")",
peg$c13 = peg$literalExpectation(")", false),
peg$c14 = function(expr) { return expr; },
peg$c15 = peg$otherExpectation("integer"),
peg$c16 = /^[0-9]/,
peg$c17 = peg$classExpectation([["0", "9"]], false, false),
peg$c18 = function() { return parseInt(text(), 10); },
peg$c19 = peg$otherExpectation("whitespace"),
peg$c20 = /^[ \t\n\r]/,
peg$c21 = peg$classExpectation([" ", "\t", "\n", "\r"], false, false),
peg$currPos = 0,
peg$savedPos = 0,
peg$posDetailsCache = [{ line: 1, column: 1 }],
peg$maxFailPos = 0,
peg$maxFailExpected = [],
peg$silentFails = 0,
peg$result;
if ("startRule" in options) {
if (!(options.startRule in peg$startRuleFunctions)) {
throw new Error("Can't start parsing from rule \"" + options.startRule + "\".");
}
peg$startRuleFunction = peg$startRuleFunctions[options.startRule];
}
function text() {
return input.substring(peg$savedPos, peg$currPos);
}
function location() {
return peg$computeLocation(peg$savedPos, peg$currPos);
}
function expected(description, location) {
location = location !== void 0 ? location : peg$computeLocation(peg$savedPos, peg$currPos)
throw peg$buildStructuredError(
[peg$otherExpectation(description)],
input.substring(peg$savedPos, peg$currPos),
location
);
}
function error(message, location) {
location = location !== void 0 ? location : peg$computeLocation(peg$savedPos, peg$currPos)
throw peg$buildSimpleError(message, location);
}
function peg$literalExpectation(text, ignoreCase) {
return { type: "literal", text: text, ignoreCase: ignoreCase };
}
function peg$classExpectation(parts, inverted, ignoreCase) {
return { type: "class", parts: parts, inverted: inverted, ignoreCase: ignoreCase };
}
function peg$anyExpectation() {
return { type: "any" };
}
function peg$endExpectation() {
return { type: "end" };
}
function peg$otherExpectation(description) {
return { type: "other", description: description };
}
function peg$computePosDetails(pos) {
var details = peg$posDetailsCache[pos], p;
if (details) {
return details;
} else {
p = pos - 1;
while (!peg$posDetailsCache[p]) {
p--;
}
details = peg$posDetailsCache[p];
details = {
line: details.line,
column: details.column
};
while (p < pos) {
if (input.charCodeAt(p) === 10) {
details.line++;
details.column = 1;
} else {
details.column++;
}
p++;
}
peg$posDetailsCache[pos] = details;
return details;
}
}
function peg$computeLocation(startPos, endPos) {
var startPosDetails = peg$computePosDetails(startPos),
endPosDetails = peg$computePosDetails(endPos);
return {
start: {
offset: startPos,
line: startPosDetails.line,
column: startPosDetails.column
},
end: {
offset: endPos,
line: endPosDetails.line,
column: endPosDetails.column
}
};
}
function peg$fail(expected) {
if (peg$currPos < peg$maxFailPos) { return; }
if (peg$currPos > peg$maxFailPos) {
peg$maxFailPos = peg$currPos;
peg$maxFailExpected = [];
}
peg$maxFailExpected.push(expected);
}
function peg$buildSimpleError(message, location) {
return new peg$SyntaxError(message, null, null, location);
}
function peg$buildStructuredError(expected, found, location) {
return new peg$SyntaxError(
peg$SyntaxError.buildMessage(expected, found),
expected,
found,
location
);
}
function peg$parseExpression() {
var s0, s1, s2, s3, s4, s5, s6, s7;
s0 = peg$currPos;
s1 = peg$parseTerm();
if (s1 !== peg$FAILED) {
s2 = [];
s3 = peg$currPos;
s4 = peg$parse_();
if (s4 !== peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 43) {
s5 = peg$c0;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c1); }
}
if (s5 === peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 45) {
s5 = peg$c2;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c3); }
}
}
if (s5 !== peg$FAILED) {
s6 = peg$parse_();
if (s6 !== peg$FAILED) {
s7 = peg$parseTerm();
if (s7 !== peg$FAILED) {
s4 = [s4, s5, s6, s7];
s3 = s4;
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
while (s3 !== peg$FAILED) {
s2.push(s3);
s3 = peg$currPos;
s4 = peg$parse_();
if (s4 !== peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 43) {
s5 = peg$c0;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c1); }
}
if (s5 === peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 45) {
s5 = peg$c2;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c3); }
}
}
if (s5 !== peg$FAILED) {
s6 = peg$parse_();
if (s6 !== peg$FAILED) {
s7 = peg$parseTerm();
if (s7 !== peg$FAILED) {
s4 = [s4, s5, s6, s7];
s3 = s4;
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
}
if (s2 !== peg$FAILED) {
peg$savedPos = s0;
s1 = peg$c4(s1, s2);
s0 = s1;
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
return s0;
}
function peg$parseTerm() {
var s0, s1, s2, s3, s4, s5, s6, s7;
s0 = peg$currPos;
s1 = peg$parseFactor();
if (s1 !== peg$FAILED) {
s2 = [];
s3 = peg$currPos;
s4 = peg$parse_();
if (s4 !== peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 42) {
s5 = peg$c5;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c6); }
}
if (s5 === peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 47) {
s5 = peg$c7;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c8); }
}
}
if (s5 !== peg$FAILED) {
s6 = peg$parse_();
if (s6 !== peg$FAILED) {
s7 = peg$parseFactor();
if (s7 !== peg$FAILED) {
s4 = [s4, s5, s6, s7];
s3 = s4;
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
while (s3 !== peg$FAILED) {
s2.push(s3);
s3 = peg$currPos;
s4 = peg$parse_();
if (s4 !== peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 42) {
s5 = peg$c5;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c6); }
}
if (s5 === peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 47) {
s5 = peg$c7;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c8); }
}
}
if (s5 !== peg$FAILED) {
s6 = peg$parse_();
if (s6 !== peg$FAILED) {
s7 = peg$parseFactor();
if (s7 !== peg$FAILED) {
s4 = [s4, s5, s6, s7];
s3 = s4;
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
} else {
peg$currPos = s3;
s3 = peg$FAILED;
}
}
if (s2 !== peg$FAILED) {
peg$savedPos = s0;
s1 = peg$c9(s1, s2);
s0 = s1;
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
return s0;
}
function peg$parseFactor() {
var s0, s1, s2, s3, s4, s5;
s0 = peg$currPos;
if (input.charCodeAt(peg$currPos) === 40) {
s1 = peg$c10;
peg$currPos++;
} else {
s1 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c11); }
}
if (s1 !== peg$FAILED) {
s2 = peg$parse_();
if (s2 !== peg$FAILED) {
s3 = peg$parseExpression();
if (s3 !== peg$FAILED) {
s4 = peg$parse_();
if (s4 !== peg$FAILED) {
if (input.charCodeAt(peg$currPos) === 41) {
s5 = peg$c12;
peg$currPos++;
} else {
s5 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c13); }
}
if (s5 !== peg$FAILED) {
peg$savedPos = s0;
s1 = peg$c14(s3);
s0 = s1;
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
if (s0 === peg$FAILED) {
s0 = peg$parseInteger();
}
return s0;
}
function peg$parseInteger() {
var s0, s1, s2, s3;
peg$silentFails++;
s0 = peg$currPos;
s1 = peg$parse_();
if (s1 !== peg$FAILED) {
s2 = [];
if (peg$c16.test(input.charAt(peg$currPos))) {
s3 = input.charAt(peg$currPos);
peg$currPos++;
} else {
s3 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c17); }
}
if (s3 !== peg$FAILED) {
while (s3 !== peg$FAILED) {
s2.push(s3);
if (peg$c16.test(input.charAt(peg$currPos))) {
s3 = input.charAt(peg$currPos);
peg$currPos++;
} else {
s3 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c17); }
}
}
} else {
s2 = peg$FAILED;
}
if (s2 !== peg$FAILED) {
peg$savedPos = s0;
s1 = peg$c18();
s0 = s1;
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
} else {
peg$currPos = s0;
s0 = peg$FAILED;
}
peg$silentFails--;
if (s0 === peg$FAILED) {
s1 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c15); }
}
return s0;
}
function peg$parse_() {
var s0, s1;
peg$silentFails++;
s0 = [];
if (peg$c20.test(input.charAt(peg$currPos))) {
s1 = input.charAt(peg$currPos);
peg$currPos++;
} else {
s1 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c21); }
}
while (s1 !== peg$FAILED) {
s0.push(s1);
if (peg$c20.test(input.charAt(peg$currPos))) {
s1 = input.charAt(peg$currPos);
peg$currPos++;
} else {
s1 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c21); }
}
}
peg$silentFails--;
if (s0 === peg$FAILED) {
s1 = peg$FAILED;
if (peg$silentFails === 0) { peg$fail(peg$c19); }
}
return s0;
}
peg$result = peg$startRuleFunction();
if (peg$result !== peg$FAILED && peg$currPos === input.length) {
return peg$result;
} else {
if (peg$result !== peg$FAILED && peg$currPos < input.length) {
peg$fail(peg$endExpectation());
}
throw peg$buildStructuredError(
peg$maxFailExpected,
peg$maxFailPos < input.length ? input.charAt(peg$maxFailPos) : null,
peg$maxFailPos < input.length
? peg$computeLocation(peg$maxFailPos, peg$maxFailPos + 1)
: peg$computeLocation(peg$maxFailPos, peg$maxFailPos)
);
}
}
return {
SyntaxError: peg$SyntaxError,
parse: peg$parse
};
})();
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