John
e4c008bd4b
ast: - Document operators - Parameterize Pat with Annotation - Consolidate Path and Lit into "Value" (Expr) - Consolidate NamedRecord/Namedtuple into PatOp::TypePrefixed - Allow Pat<Pat,*> patterns - Additional helper functions on Expr and Pat lexer: - Support inner-doc comment syntax `//!` - Cleans up `///` or `//!` prefix parser: - Make Parse::Prec `Default` - Allow expression elision after `..`/`..=` - Fix Parser::consume not updating elide_do state - Add token splitting, to make `&&Expr` and `&&Pat` easier - error: Embed Pat precedence in ParseError
67 lines
2.1 KiB
Plaintext
67 lines
2.1 KiB
Plaintext
//! Sample doughlang code
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enum Expr {
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Atom (f64),
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Op (char, [Expr]),
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}
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fn execute(expr: Expr) -> f64 {
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match expr {
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Expr::Atom(value) => value,
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Expr::Op('*', [lhs, rhs]) => execute(lhs) * execute(rhs),
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Expr::Op('/', [lhs, rhs]) => execute(lhs) / execute(rhs),
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Expr::Op('%', [lhs, rhs]) => execute(lhs) % execute(rhs),
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Expr::Op('+', [lhs, rhs]) => execute(lhs) + execute(rhs),
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Expr::Op('-', [lhs, rhs]) => execute(lhs) - execute(rhs),
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// Expr::Op('>', [lhs, rhs]) => (execute(lhs) as u64 >> execute(rhs) as u64) as f64,
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// Expr::Op('<', [lhs, rhs]) => (execute(lhs) as u64 << execute(rhs) as u64) as f64,
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Expr::Op('-', [lhs]) => - execute(lhs),
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other => {
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panic("Unknown operation: " + fmt(other))
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}
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}
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}
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/// Formats an expression to a string
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fn fmt_expr(expr: Expr) -> str {
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match expr {
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Expr::Atom(value) => fmt(value),
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Expr::Op(operator, [lhs, rhs]) => fmt('(', fmt_expr(lhs), ' ', operator, ' ', fmt_expr(rhs), ')'),
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Expr::Op(operator, [rhs]) => fmt(operator, fmt_expr(rhs)),
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_ => println("Unexpected expr: ", expr),
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}
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}
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/// Prints an expression
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fn print_expr(expr: Expr) {
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println(fmt_expr(expr))
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}
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/// Parses expressions
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fn parse(line: [char], power: i32) -> (Expr, [char]) {
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fn map((expr, line): (Expr, [char]), f: fn(Expr) -> Expr) -> (Expr, [char]) {
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(f(expr), line)
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}
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line = space(line);
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let (lhs, line) = match line {
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['0'..'9', ..] => number(line),
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['(', ..rest] => match parse(rest, Power::None) {
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(expr, [')', ..rest]) => (expr, rest),
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(expr, rest) => panic(fmt("Expected ')', got ", expr, ", ", rest)),
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},
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[op, ..rest] => parse(rest, pre_bp(op)).map(|lhs| Expr::Op(op, [lhs])),
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_ => panic("Unexpected end of input"),
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};
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while let [op, ..rest] = space(line) {
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let (before, after) = inf_bp(op);
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if before < power {
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break;
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};
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(lhs, line) = parse(rest, after).map(|rhs| Expr::Op(op, [lhs, rhs]));
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};
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(lhs, line)
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}
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