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refactor: use switch statement in parser loop for readability

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Replaces the deeply nested if-chain inside the Pratt parser loop in `src/engine/parser.ts` with a `switch` statement over token types. Introduces a labeled `loop: for(;;)` to maintain accurate `continue`/`break` semantics while greatly enhancing the visual parsing and extensibility of the logic without hurting evaluation speed.

Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>
This commit is contained in:
google-labs-jules[bot] 2026-08-19 11:29:56 +00:00
parent 868a34497b
commit 7adbbb6754
1 changed files with 120 additions and 103 deletions
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153
src/engine/parser.ts
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@ -204,114 +204,131 @@ class Parser {
if (!lhs) return null; if (!lhs) return null;
for (;;) { loop: for (;;) {
tk = this.peek(); tk = this.peek();
if (!tk) break; if (!tk) break;
if (tk.t === "percent") { switch (tk.t) {
if (PREC.POSTFIX < minPrec) break; case "percent": {
if (PREC.POSTFIX < minPrec) break loop;
this.i++; this.i++;
lhs = { k: "pct", x: lhs }; lhs = { k: "pct", x: lhs };
continue; continue loop;
} }
if (tk.t === "bang") { case "bang": {
if (PREC.POSTFIX < minPrec) break; if (PREC.POSTFIX < minPrec) break loop;
this.i++; this.i++;
lhs = { k: "fact", x: lhs }; lhs = { k: "fact", x: lhs };
continue; continue loop;
} }
if (tk.t === "unit") { case "unit": {
if (PREC.POSTFIX < minPrec) break; if (PREC.POSTFIX < minPrec) break loop;
this.i++; this.i++;
lhs = { k: "unit", x: lhs, unit: tk.unit }; lhs = { k: "unit", x: lhs, unit: tk.unit };
continue; continue loop;
} }
if (tk.t === "currency") { case "currency": {
if (PREC.POSTFIX < minPrec) break; if (PREC.POSTFIX < minPrec) break loop;
this.i++; this.i++;
lhs = { k: "curr", x: lhs, code: tk.code }; lhs = { k: "curr", x: lhs, code: tk.code };
continue; continue loop;
} }
if (tk.t === "scale") { case "scale": {
if (PREC.POSTFIX < minPrec) break; if (PREC.POSTFIX < minPrec) break loop;
this.i++; this.i++;
lhs = { k: "scale", x: lhs, mult: tk.mult, label: "" }; lhs = { k: "scale", x: lhs, mult: tk.mult, label: "" };
continue; continue loop;
} }
if (tk.t === "op" && tk.op === "pow") { case "op": {
if (PREC.POW < minPrec) break; switch (tk.op) {
case "pow": {
if (PREC.POW < minPrec) break loop;
const save = this.i; const save = this.i;
this.i++; this.i++;
const r = this.parseExpr(PREC.POW); const r = this.parseExpr(PREC.POW);
if (!r) { this.i = save; break; } if (!r) { this.i = save; break loop; }
lhs = { k: "bin", op: "pow", l: lhs, r }; lhs = { k: "bin", op: "pow", l: lhs, r };
continue; continue loop;
} }
if (tk.t === "op" && (tk.op === "mul" || tk.op === "div" || tk.op === "mod")) { case "mul":
if (PREC.MUL < minPrec) break; case "div":
case "mod": {
if (PREC.MUL < minPrec) break loop;
const save = this.i; const save = this.i;
this.i++; this.i++;
const r = this.parseExpr(PREC.MUL + 1); const r = this.parseExpr(PREC.MUL + 1);
if (!r) { this.i = save; break; } if (!r) { this.i = save; break loop; }
lhs = { k: "bin", op: tk.op, l: lhs, r }; lhs = { k: "bin", op: tk.op, l: lhs, r };
continue; continue loop;
} }
if (tk.t === "pctop" && (tk.op === "of" || tk.op === "off" || tk.op === "on")) { case "plus":
if (!(lhs.k === "pct" || lhs.k === "var" || lhs.k === "pctop")) { case "minus": {
this.i++; if (PREC.ADD < minPrec) break loop;
continue;
}
if (PREC.MUL < minPrec) break;
const save = this.i;
this.i++;
const r = this.parseExpr(PREC.MUL + 1);
if (!r) { this.i = save; break; }
lhs = { k: "pctop", op: tk.op, l: lhs, r };
continue;
}
if (tk.t === "lparen" || tk.t === "const" || tk.t === "func" || (tk.t === "word" && this.vars.has(tk.raw))) {
if (PREC.MUL < minPrec) break;
const save = this.i;
const r = this.parseExpr(PREC.MUL + 1);
if (!r) { this.i = save; break; }
lhs = { k: "bin", op: "mul", l: lhs, r };
continue;
}
if (tk.t === "op" && (tk.op === "plus" || tk.op === "minus")) {
if (PREC.ADD < minPrec) break;
const save = this.i; const save = this.i;
this.i++; this.i++;
const r = this.parseExpr(PREC.ADD + 1); const r = this.parseExpr(PREC.ADD + 1);
if (!r) { this.i = save; break; } if (!r) { this.i = save; break loop; }
lhs = { k: "bin", op: tk.op, l: lhs, r }; lhs = { k: "bin", op: tk.op, l: lhs, r };
continue; continue loop;
} }
if (tk.t === "bitop") { }
if (PREC.BIT < minPrec) break; break loop;
}
case "pctop": {
if (tk.op === "of" || tk.op === "off" || tk.op === "on") {
if (!(lhs.k === "pct" || lhs.k === "var" || lhs.k === "pctop")) {
this.i++;
continue loop;
}
if (PREC.MUL < minPrec) break loop;
const save = this.i; const save = this.i;
this.i++; this.i++;
const r = this.parseExpr(PREC.BIT + 1); const r = this.parseExpr(PREC.MUL + 1);
if (!r) { this.i = save; break; } if (!r) { this.i = save; break loop; }
lhs = { k: "bit", op: tk.op, l: lhs, r }; lhs = { k: "pctop", op: tk.op, l: lhs, r };
continue; continue loop;
} }
if (tk.t === "conv") { if (tk.op.startsWith("as_pct") || tk.op.endsWith("what_is")) {
if (PREC.CONV < minPrec) break; if (PREC.CONV < minPrec) break loop;
const save = this.i;
this.i++;
const target = this.parseTarget();
if (!target) { this.i = save; break; }
lhs = { k: "conv", x: lhs, target: this.tryHistoricalDate(target) };
continue;
}
if (tk.t === "pctop" && (tk.op.startsWith("as_pct") || tk.op.endsWith("what_is"))) {
if (PREC.CONV < minPrec) break;
const save = this.i; const save = this.i;
this.i++; this.i++;
const r = this.parseExpr(PREC.ADD); const r = this.parseExpr(PREC.ADD);
if (!r) { this.i = save; break; } if (!r) { this.i = save; break loop; }
lhs = { k: "pctop", op: tk.op, l: lhs, r }; lhs = { k: "pctop", op: tk.op, l: lhs, r };
continue; continue loop;
}
break loop;
}
case "lparen":
case "const":
case "func":
case "word": {
if (tk.t === "word" && !this.vars.has(tk.raw)) break loop;
if (PREC.MUL < minPrec) break loop;
const save = this.i;
const r = this.parseExpr(PREC.MUL + 1);
if (!r) { this.i = save; break loop; }
lhs = { k: "bin", op: "mul", l: lhs, r };
continue loop;
}
case "bitop": {
if (PREC.BIT < minPrec) break loop;
const save = this.i;
this.i++;
const r = this.parseExpr(PREC.BIT + 1);
if (!r) { this.i = save; break loop; }
lhs = { k: "bit", op: tk.op, l: lhs, r };
continue loop;
}
case "conv": {
if (PREC.CONV < minPrec) break loop;
const save = this.i;
this.i++;
const target = this.parseTarget();
if (!target) { this.i = save; break loop; }
lhs = { k: "conv", x: lhs, target: this.tryHistoricalDate(target) };
continue loop;
}
} }
break; break;