I can't find the relevant thread now, but I'm sure you brought this issue up over a year ago. The code generated is supposed to be: var x = 10; var y = 10; var z = 10; var _cmp1 = y; x == _cmp1 && _cmp1 == z; The problem is that transformation is currently implemented as a hack on top of the compiler, and "=" wasn't one of the symbols in the special list that gets "corrected." I've pushed a patch that adds a fix to the hack, but I'm going to rework the implementation later. One issue this raises is order of evaluation. Doing that transformation on n expressions and preserving left-to-right evaluation order means introducing n temporary variables in the general case. This problem also comes up when defining setf expanders for places. At this point Parenscript might as well adopt the Scheme policy of "order of argument evaluation is undefined" officially. Also Henrik brings up a good point - the "=" form should expand to "===." "==" is more like EQUAL. Vladimir 2010/3/2 Daniel Gackle <danielgackle@gmail.com>:
(let ((x 10) (y 10) (z 10)) (= x y z))
is true Common Lisp, but the PS equivalent...
var x = 10; var y = 10; var z = 10; x == y == z;
... is false. The left operand of the second == is actually x==y, which evalutes to true, and true==z of course is false. An equivalent in CL might be:
(equal (equal x y) z)
Perverse side note: the above example doesn't work if you assign 1 to the variables because in JS, the following is true:
1 == true
I didn't know this. JS still manages to shock me sometimes.
Daniel
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