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ref: 450ec696ee46f79159395a89c9a97bc8354616ba
parent: c3779afdd6452b40c27359a88af548e93635b595
author: Ori Bernstein <[email protected]>
date: Fri Dec 6 06:53:44 EST 2019

hoc: don't nest calls to follow() when lexing ++/+= and --/-= (#287)

The code had a nested use of the follow() function that could cause +=+
and -=- to register as ++ and --.  The first follow() to execute could
consume a character and match and then the second follow() could consume
another character and match.  For example i-=-10 would result in a syntax
error and i-=- would decrement i.

(imported from plan9port commit f1dd3f065a97f57bf59db2e3284868e181734159)

--- a/sys/src/cmd/hoc/hoc.y

+++ b/sys/src/cmd/hoc/hoc.y

@@ -214,8 +214,8 @@

 		return STRING;

 	}

 	switch (c) {

-	case '+':	return follow('+', INC, follow('=', ADDEQ, '+'));

-	case '-':	return follow('-', DEC, follow('=', SUBEQ, '-'));

+	case '+':	return follow('+', INC, '+') == INC ? INC : follow('=', ADDEQ, '+');

+	case '-':	return follow('-', DEC, '-') == DEC ? DEC : follow('=', SUBEQ, '-');

 	case '*':	return follow('=', MULEQ, '*');

 	case '/':	return follow('=', DIVEQ, '/');

 	case '%':	return follow('=', MODEQ, '%');