bug I think, but a partial workaround
pD =: 1!:2&2
''[(pD@:('norm ',":)) :. (pD@:('inverse ',":))^:_1^:2 'abc'
inverse abc
inverse inverse abc
doesn't help with _1 0 , or _1 _1. Also affects ^:v
''[0 _1 (pD@:('norm ',":@:])) :. (pD@:('inverse ',":@:]))(^:[ ) 'abc'
norm abc
inverse abc
there is also a problem with any multiple argument:
''[ (pD@:('norm ',":@:])) :. (pD@:('inverse ',":@:]))^: 0 1 'abc'
norm abc
norm abc
can be partial fixed with removing 0s when the v argument contains multiple
items :
scalarize =: {.^:((,1) -: $)
power =: 2 : 'u^:(0 (scalarize@:-.~^:(1<#@:]) *) v"_) ^:([: | 0
scalarize@:-.~^:(1<#@:]) v"_)'
''[ (pD@:('norm ',":@:])) :. (pD@:('inverse ',":@:]))power _2 'abc'
inverse abc
inverse inverse abc
''[ (pD@:('norm ',":@:])) :. (pD@:('inverse ',":@:]))power 0 2 'abc'
norm abc
norm norm abc
''[ 0 _2 (pD@:('norm ',":@:])) :. (pD@:('inverse ',":@:]))power [ 'abc'
inverse abc
inverse inverse abc
just _1 _1 remains a problem, but could be fixed with nub.
----- Original Message -----
From: "[email protected]" <[email protected]>
To: [email protected]
Cc:
Sent: Tuesday, July 15, 2014 11:57:26 AM
Subject: [Jprogramming] Why does u^:_2 execute u?
u^:_1 executes the inverse of u, but u&:_2, or any other value
of n containing a negative value, executes u first. I am just wondering why
'' [ (>:@[ smoutput@('+',":)) :. (<:@[ smoutput@('-',":)) ^:(_1) 0
-0
'' [ (>:@[ smoutput@('+',":)) :. (<:@[ smoutput@('-',":)) ^:(_1 0) 0
+0
-0
'' [ (>:@[ smoutput@('+',":)) :. (<:@[ smoutput@('-',":)) ^:(_2) 0
+0
-0
-_1
The +0 lines are the surprise executions of u. The execution seems to mean
business:
[: :. (smoutput@('inverse ',":))^:_1 'abc'
inverse abc
[: :. (smoutput@('inverse ',":))^:_1 _1 'abc'
|domain error
| [: :.(smoutput@('inverse ',":))^:_1 _1'abc'
I just can't imagine what the business might be.
Henry Rich
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