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#154 integrate does not produce asinh ←	↑	→ #156 Axiom crashes when compiling simple Taylor code

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

Edit detail for #155 failed coercion between Expression Fraction Integer and Expression Float in exponents revision 2 of 2

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Editor: kratt6 Time: 2007/12/28 13:22:59 GMT-8
Note: redundancy

added:

From kratt6 Fri Dec 28 13:22:59 -0800 2007
From: kratt6
Date: Fri, 28 Dec 2007 13:22:59 -0800
Subject: redundancy
Message-ID: <20071228132259-0800@axiom-wiki.newsynthesis.org>

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

This fails

fricas

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

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

(1)

Type: Expression(Float)

fricas

% :: Expression Fraction Integer

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

(2)

Type: Expression(Fraction(Integer))

fricas

% :: Expression Float

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

(3)

Type: Expression(Float)

But this works

fricas

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

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

(4)

Type: Expression(Integer)

fricas

% :: 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

fricas

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

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

(6)

Type: Expression(Fraction(Integer))

fricas

%::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

fricas

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

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

(8)

Type: Expression(Fraction(Integer))

then why?

fricas

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