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rpncalc-v4
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fixed random throws + non-backtracing stream

This commit is contained in:
Aidan K. Ewart 2020-05-20 00:11:31 +01:00
parent e29e83789c
commit ccff5a14a3
1 changed files with 20 additions and 18 deletions
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38
parse.js
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@ -65,7 +65,7 @@ const attempt = (parser) => (stream) => {
const or = (a, b) => (stream) => {
let aout = a(stream);
if (aout.parsed === null) {
return b(stream);
return b(aout.stream);
} else {
return aout;
}
@ -74,15 +74,15 @@ const or = (a, b) => (stream) => {
/* (parser) */
const parens = (parser) => (stream) => {
let a = parseSyntax("(", stream);
if (a === null) {
return {parsed:null, stream:stream};
if (a.parsed === null) {
return {parsed:null, stream:a.stream};
}
let dat = parser(stream);
a = parseSyntax(")", stream);
if (a === null) {
let dat = parser(a.stream);
a = parseSyntax(")", dat.stream);
if (a.parsed === null) {
throw 'mismatched parens!';
}
return dat;
return {parsed:dat.parsed, stream:a.stream};
}
/* [parser] */
@ -90,6 +90,7 @@ const many = (parser) => (stream) => {
let parsed = [];
for (let i = parser(stream); i.parsed !== null; i = parser(stream)) {
parsed.push(i.parsed);
stream = i.stream;
}
return {parsed:parsed, stream:stream};
}
@ -160,30 +161,31 @@ const parseSyntax = (syntax, stream) => {
const parseName = (stream) => {
let id = parseIdent(stream);
if (id.parsed === null) {
return {parsed:null, stream:stream};
return {parsed:null, stream:id.stream};
}
let syn = parseSyntax(";", stream);
let syn = parseSyntax(";", id.stream);
if (syn.parsed === null) {
throw 'could not parse name!'
}
return {parsed:id.parsed.val, stream:stream};
return {parsed:id.parsed.val, stream:syn.stream};
}
/* takes in stream, outputs parsed item or null - FAILABLE */
const parseLambda = (stream) => {
let name = attempt(parseName)(stream).parsed;
if (name === null) {
name = "";
let name = attempt(parseName)(stream);
if (name.parsed === null) {
name.parsed = "";
}
let args = many(parseIdent)(stream).parsed;
if (parseSyntax("->", stream).parsed === null) {
let args = many(parseIdent)(name.stream);
let syn = parseSyntax("->", args.stream);
if (syn.parsed === null) {
throw 'no lambda body found!';
}
let body = parseExprs(stream).parsed; // .parsed should never be null, but anyway...
if (body === null) {
let body = parseExprs(syn.stream); // .parsed should never be null, but anyway...
if (body.parsed === null) {
throw 'no lambda body found!';
}
return {parsed:{type:"func", name:name, args:args, body:body}, stream:stream};
return {parsed:{type:"func", name:name.parsed, args:args.parsed, body:body.parsed}, stream:body.stream};
}
/* takes in stream, outputs parsed item or null */