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Re: [Axiom-developer] about Expression Integer
From: |
Ralf Hemmecke |
Subject: |
Re: [Axiom-developer] about Expression Integer |
Date: |
Fri, 24 Feb 2006 15:14:49 +0100 |
User-agent: |
Thunderbird 1.5 (X11/20051201) |
Hi Bill,
(4) -> Z:Float:=1
(4) 1.0
Type: Float
(5) -> Z::INT <---- this is a conversion of Float to INT
(5) 1
Type: Integer
Now, I learned something new. And maybe Axiom behaves here different
from Aldor.
In Aldor "Z::Integer" is just syntactic sugar for writing
"coerce(Z)@Integer" (which looks for a function
coerce: Float -> Integer
currently in scope and applies it).
In Aldor there is (almost) never a coercion (type cast) done
automatically. Of course you can write something like
aldor -gloop
#include "aldor"
#include "aldorinterp"
Z:SingleFloat := 1;
But there is no coercion involved. Since SingleFloat is of type
ArtithmeticType.
%10 >> SingleFloat has ArithmeticType
T @ Boolean
%11 >> ArithmeticType
@ Category == AdditiveType with
1: %
*: (%, %) -> %
^: (%, MachineInteger) -> %
commutative?: Boolean
one?: % -> Boolean
times!: (%, %) -> %
default
local copy?: Boolean == % has CopyableType
one?(a: %): Boolean == ..
times!(a: %, b: %): % == ..
The 1 is simply interpreted as the constant 1 in SingleFloat.
Now the following is also clear.
%14 >> Z := 2
.....^
[L14 C6] #1 (Error) No meaning for integer-style literal `2'.
%15 >> Z:=2.0
2 @ SingleFloat
%16 >> import from Integer
%17 >> Z := 2
.....^
[L17 C6] #1 (Error) There is no suitable interpretation for the expression 2
The context requires an expression of type SingleFloat.
The possible types of the right hand side (`2') are:
-- AldorInteger
I like that Aldor does nothing automatically.
Ralf
PS: To be correct there is one case that comes to my mind where the
Aldor compiler is a bit more relaxed.
See "Curtesy conversions" at
http://www.aldor.org/docs/HTML/chap7.html#6
- Re: [Axiom-developer] about Expression Integer, (continued)
- Re: [Axiom-developer] about Expression Integer, William Sit, 2006/02/21
- RE: [Axiom-developer] about Expression Integer, Bill Page, 2006/02/21
- RE: [Axiom-developer] about Expression Integer, Page, Bill, 2006/02/24
- RE: [Axiom-developer] about Expression Integer, Page, Bill, 2006/02/24
- Re: [Axiom-developer] about Expression Integer,
Ralf Hemmecke <=
- RE: [Axiom-developer] about Expression Integer, Page, Bill, 2006/02/24