MathAction #155 failed coercion between Expression Fraction Integer and Expression Float in exponents

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  - #155 failed coercion between Expression Fraction Integer and Expression Float in exponents <-- You are here.

This fails

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(1) -> exp(-0.02*t)

$\label{eq1}{e}^{-{{0.02}\ t}}$

(1)

Type: Expression(Float)

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% :: Expression Fraction Integer

$\label{eq2}{e}^{-{{\frac{1}{50}}\ t}}$

(2)

Type: Expression(Fraction(Integer))

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% :: Expression Float

$\label{eq3}{e}^{-{{0.02}\ t}}$

(3)

Type: Expression(Float)

But this works

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exp(-1*(1/50)*t)

$\label{eq4}{e}^{-{\frac{t}{50}}}$

(4)

Type: Expression(Integer)

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% :: Expression Float

$\label{eq5}{e}^{-{{0.02}\ t}}$

(5)

Type: Expression(Float)

Why are these expressions treated differently?

How can convert the first one to the second?

EXPR FRAC INT doesn't coerce to EXPR FLOAT --unknown, Tue, 10 May 2005 17:54:24 -0500 reply

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(1/2*x)::EXPR FRAC INT

$\label{eq6}{\frac{1}{2}}\ x$

(6)

Type: Expression(Fraction(Integer))

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%::EXPR FLOAT

$\label{eq7}{0.5}\ x$

(7)

Type: Expression(Float)

Is Axiom confused? I am. --Bill Page, Tue, 10 May 2005 18:35:04 -0500 reply

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exp(-0.02*t) :: Expression Fraction Integer

$\label{eq8}{e}^{-{{\frac{1}{50}}\ t}}$

(8)

Type: Expression(Fraction(Integer))

then why?

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exp(-1*(1/50)*t)

$\label{eq9}{e}^{-{\frac{t}{50}}}$

(9)

Type: Expression(Integer)

Is Axiom confused about the definition of the type Expression Integer? What exactly is it that is supposed to be an Integer in each case above?

redundancy --kratt6, Fri, 28 Dec 2007 13:22:59 -0800 reply

Category: Axiom Compiler => Axiom Library Status: open => rejected

Expression R builds expressions with coefficients from R. Since Expression is closed under division, EXPR INT and EXPR FRAC INT cover the same amount of expressions. It seems to be part of axiom's philosophy not to support redundant application of domain constructors, at least in the interpreter. Other examples are FRAC FRAC INT or COMPLEX COMPLEX INT.

Martin

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