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Science Forum Index » Math - Symbolic Forum » odd behaviour of `if`
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| Author |
Message |
| kilian heckrodt |
 Posted: Tue Apr 24, 2007 7:40 pm |
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Guest
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Hi !
I'm getting bugged by somewhat odd (and for me unexpected) behaviour of
maple:
subs(i=5,`if`(i mod 5 = 0,1,i)) = 5, but `if`(5 mod 5 = 0,1,5) = 1
and in sum and product statement the `if` behaves like with the
substitution.
What's the reason for this behaviour and is there a workaround?
In other words how can if use the `if` in formulas/products/sums ? |
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| G. A. Edgar |
| Posted: Wed Apr 25, 2007 7:15 am |
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Guest
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In article <f0m82h$qcl$02$1@news.t-online.com>, kilian heckrodt
<kilianheckrodt@yahoo.com> wrote:
Quote: Hi !
I'm getting bugged by somewhat odd (and for me unexpected) behaviour of
maple:
subs(i=5,`if`(i mod 5 = 0,1,i)) = 5, but `if`(5 mod 5 = 0,1,5) = 1
and in sum and product statement the `if` behaves like with the
substitution.
What's the reason for this behaviour and is there a workaround?
In other words how can if use the `if` in formulas/products/sums ?
You want to evaluate `if`(i mod 5 = 0,1,i) before or after you
substitute i=5? It makes a difference. Use quotes ' ' to
delay evaluation. You can use "eval" instead of "subs" . I
prefer to use "piecewise" instead of "`if`" , but here
I guess it doesn't matter.
eval('`if`(i mod 5 = 0,1,i)',i=5);
1
eval(`if`(i mod 5 = 0,1,i),i=5);
5
eval(piecewise(i mod 5 = 0,1,i),i=5);
5
eval('piecewise(i mod 5 = 0,1,i)',i=5);
1
--
G. A. Edgar http://www.math.ohio-state.edu/~edgar/ |
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