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Closes #1547 , which was caused by misspelled/nonexistent types being interpreted as type variables. In #1550 I proposed one solution to the problem, namely, to stop implicitly quantifying types and require explicit `forall` on any polymorphic type. This PR represents an alternative solution: to keep implicit quantification but require all types to start with an uppercase letter, as in Haskell. I think I like this one better but I'm open to feedback. Specifically, with this PR: - All built-in type constructors (`Int`, `Cmd`, `Unit`, etc.) must start with a capital letter - Type variables: - Must start with a lowercase letter or underscore - May not be named a lowercase version of a type constructor, *e.g.* `int` - This is important so that old code with lowercase types is not silently accepted by parsing the former types as implicitly quantified type variables; even in cases where old code no longer typechecks, this will give better error messages. - Term variables: - May start with upper- or lowercase - May be named lowercase versions of type names, *e.g.* `let f : Int -> Int = \int. int + 1` is fine This PR obviously represents a bigger breaking change. Once we merge this we might consider adding an option to `swarm format` to be able to parse old code with lowercase types and then reformat it with uppercase, to aid in porting code. Once this is merged I will also regenerate the wiki pages that mention types. Closes #1550.
25 lines
539 B
Plaintext
25 lines
539 B
Plaintext
// A "cat" that wanders around randomly. Shows off use of the
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// 'random' command.
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let forever : Cmd Unit -> Cmd Unit = \c. c ; forever c in
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let repeat : Int -> Cmd Unit -> Cmd Unit =
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\n. \c. if (n == 0) {} {c ; repeat (n-1) c} in
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let randdir : Cmd Dir =
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d <- random 4;
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return (
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if (d == 0) {north}
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{if (d == 1) {east}
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{if (d == 2) {south} {west}}})
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in
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forever (
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n <- random 20;
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wait (10 + n);
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d <- randdir;
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turn d;
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dist <- random 10;
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repeat dist move;
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r <- random 5;
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if (r == 0) { say "meow" } {}
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)
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