51 lines
2.3 KiB
Plaintext
51 lines
2.3 KiB
Plaintext
;;;; A program that stops with something worth looking at in the frame.
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;;;;
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;;;; dev-break.flan proves an editor can find out *that* a program stopped and
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;;;; choose a restart; this one is about what the frame holds while it is
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;;;; stopped. One local of each shape the structural printer has an arm for —
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;;;; a parameter, a string, a struct, a fixed array, a bool — plus one that is
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;;;; bound only *after* the error, which is the case that must come back
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;;;; refused rather than rendered: its slot is storage nothing has written yet.
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(import agent "vendor:agent")
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(defstruct Point [x f32 y f32])
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(defstruct Boom [why i32])
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(defn look [n i64 label str] i64
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(let [p (Point {.x 1.5 .y 2.5})
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xs [10 20 30]
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flag (> n 0)
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;; Three bytes, for the three answers the character half has. A [u8]
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;; already renders as text, so a lone byte showing only its number is
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;; the one place the same data reads two ways — but only where a
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;; person is inspecting. [println] of a u8 stays a number.
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byte (u8 97) ; printable: 97 (\a)
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gap (u8 32) ; one the reader names: 32 (\space)
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ctl (u8 7)] ; no spelling: the number alone
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;; A loop, for its hidden bound: [dotimes] allocates a slot nobody named,
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;; and the listing must *hide* it rather than refuse it by an invented
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;; name — [s6] is not a variable anyone can find in this file.
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(dotimes [hop 0] (print ""))
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;; And a shadowing rebind. The checker suffixes the repeat as [label~2]
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;; so the debug info never claims one binding is the other; the listing
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;; keeps both raw spellings, because two rows both called [label] with
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;; nothing to tell them apart would be worse.
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(let [label "inner"]
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(restart-case
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(do (error (Boom {.why 7}))
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;; Never reached before the break, so [after] is a slot with nothing
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;; in it: the frame records a null for it and this is what "not bound
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;; yet" has to mean.
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(let [after (i64 99)] after))
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(carry-on [] 5)))))
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(defonce ticks i64)
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(defn main [] i32
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(agent/start "/tmp/flan-dev-locals-fallback.sock")
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(print (look 3 "hello")) (println "")
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(dotimes [i 4000]
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(agent/wait 5)
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(set ticks (+ ticks 1)))
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0)
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