Joseph Ferano
d6fc15474b
The author: "I think I prefer length over len, because then I'll use len as the variable name". One arm in check.ml, one row in the table beside it, and every (len x) in lib, test, examples, vendor, spike, docs, web, emacs, plan.org and NEXT.md rewritten. Shadowing and builtin/ had already taken most of the sting out: a (defn len ...) was legal and won in its own file, and builtin/len reached past it. What was left is that len was still a builtin — the defn earned a warning, and a wrapper had to say builtin/ at every inner call. Now there is nothing under the short name: len is an ordinary identifier in every position, which is what (let [len (length xs)] ...) wants. length takes over as shadowing's worked example rather than the feature losing one. shadow-builtin.flan, builtin-qualified.flan, pkgs/shadowed and the builtin/ rows in test_flan move to it and go on testing shadowing. A call to a len nothing defines is answered where an unknown function is, after every table and after the shadowing guard, so a program with its own len never reaches it. The sentence is said rather than guessed at — len and length are three edits apart and the did-you-mean's net is one — and the call is written back out through spell_arg, as-slice's spelling lifted out of it and now shared, so what is printed compiles. sand.flan:33 still calls the old name and is the author's to change; until it does, test_acceptance and test_session abort there. Both were run green against a copy with that one line changed. FIX.org says so.
64 lines
2.7 KiB
Plaintext
64 lines
2.7 KiB
Plaintext
;;;; (string b) — a [u8] seen as a string.
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;;;;
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;;;; The conversion emits no instructions: String and Slice _ are both %slice,
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;;;; 16 bytes at align 8. So what is worth testing is not arithmetic, it is the
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;;;; four places a zero-instruction reinterpretation could still be wrong about
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;;;; the *length* or about who owns the bytes.
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;;;;
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;;;; Run at -O2 and at -O0. The pair matters here for the same reason it
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;;;; matters for the literal-write sharp edge: a conversion that accidentally
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;;;; produced undefined behaviour would be a SIGSEGV at one level and a silent
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;;;; deletion at the other, and agreeing at one level alone proves nothing.
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;; puts and not a Flan printer: the point of this declaration is the *shim*,
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;; which takes ptr+len and NUL-terminates a copy. A shim that instead trusted
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;; the bytes to already be terminated would print the rest of the buffer for
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;; every sub-view below, and nothing inside Flan would notice.
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;;
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;; Its return is C's "some nonnegative value", not a number worth printing, so
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;; it is only shown as a sign — and it is printed through Flan's own writer,
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;; which shares stdout's buffer with puts, so the interleaving is stable.
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(declare-c c-puts [s string] i32 "puts")
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(defn shows [s string] ()
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(print "[")
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(print s)
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(print "] ")
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(print (length (bytes-view s)))
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(println ""))
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(defn main [] i32
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;; A number. The gap this closes: i64->bytes answers a [u8], every text
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;; parameter wants a string, and until now nothing joined them.
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(shows (string (i64->bytes 42)))
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(shows (string (i64->bytes -7)))
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(shows (string (i64->bytes 0)))
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;; An empty slice. Length 0, and no read of the pointer.
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(shows (string (slice (bytes-view "abc") 1 1)))
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;; A sub-view, whose length is not the underlying storage's. The bytes after
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;; index 5 are still there and must not appear.
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(let [s (bytes-view "hello world")]
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(shows (string (slice s 0 5)))
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(shows (string (slice s 6 11)))
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(shows (string (slice s 11 11))))
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;; Round trip: (bytes-view (string b)) is b, and both directions are the identity.
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(let [b (i64->bytes 1234567)]
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(print (length (bytes-view (string b))))
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(println ""))
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;; Across the declare-c boundary. The first is a sub-view — five bytes out of
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;; eleven, the sixth of which is a space and not a NUL — so a shim that did
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;; not copy would print "hello world" here.
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(let [s (bytes-view "hello world")]
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(print (if (>= (c-puts (string (slice s 0 5))) 0) "ok" "no"))
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(println ""))
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(print (if (>= (c-puts (string (i64->bytes 12345))) 0) "ok" "no"))
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(println "")
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;; And an empty one: the shim's copy of a zero-length slice is "".
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(print (if (>= (c-puts (string (slice (bytes-view "abc") 1 1))) 0) "ok" "no"))
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(println "")
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0)
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