From: Bart Schaefer <schaefer@brasslantern.com>
To: <zsh-workers@zsh.org>
Subject: Floating point modulus
Date: Sat, 10 Jan 2015 23:10:17 -0800 [thread overview]
Message-ID: <150110231017.ZM24021@torch.brasslantern.com> (raw)
In-Reply-To: <54B20E23.8090900@eastlink.ca>
On Jan 10, 9:46pm, Ray Andrews wrote:
}
} Speaking of testing, I can't get modulus to work nohow.
}
} $ echo $(( 2.5 ));
} 2.5
}
} $ echo $(( 2.5 % 2 ));
} 0
}
} ... If I'm doing something stupid there ...
Zsh implements the C modulus operator (%) directly, and it's defined
only on integers. If you try that in C it won't even compile:
error: invalid operands to binary %
Consequently the operands are silently converted to integers, instead
of the shell throwing an error.
The expectation is that you will know that zsh math is C math (same
as for why things are integer by default) and that you must do:
$ zmodload zsh/mathfunc
$ echo $(( fmod(2.5, 2) ))
0.5
The following patch would instead silently substitute the fmod() call
when using the % operator on a float. I won't commit it without some
further discussion from the group. With more effort it could be made
to do this only when FORCE_FLOAT is in effect, though I'm not sure
how many such special-cases we want to manage.
diff --git a/Src/math.c b/Src/math.c
index 438a170..6d096e0 100644
--- a/Src/math.c
+++ b/Src/math.c
@@ -288,11 +288,11 @@ static int type[TOKCOUNT] =
{
/* 0 */ LR, LR|OP_OP|OP_OPF, RL, RL, RL|OP_OP|OP_OPF,
/* 5 */ RL|OP_OP|OP_OPF, RL, RL, LR|OP_A2IO, LR|OP_A2IO,
-/* 10 */ LR|OP_A2IO, LR|OP_A2, LR|OP_A2, LR|OP_A2IO, LR|OP_A2,
+/* 10 */ LR|OP_A2IO, LR|OP_A2, LR|OP_A2, LR|OP_A2, LR|OP_A2,
/* 15 */ LR|OP_A2, LR|OP_A2IO, LR|OP_A2IO, LR|OP_A2IR, LR|OP_A2IR,
/* 20 */ LR|OP_A2IR, LR|OP_A2IR, LR|OP_A2IR, LR|OP_A2IR, BOOL|OP_A2IO,
/* 25 */ BOOL|OP_A2IO, LR|OP_A2IO, RL|OP_OP, RL|OP_OP, RL|OP_E2,
-/* 30 */ RL|OP_E2, RL|OP_E2, RL|OP_E2, RL|OP_E2, RL|OP_E2IO,
+/* 30 */ RL|OP_E2, RL|OP_E2, RL|OP_E2, RL|OP_E2, RL|OP_E2,
/* 35 */ RL|OP_E2IO, RL|OP_E2IO, RL|OP_E2IO, RL|OP_E2IO, RL|OP_E2IO,
/* 40 */ BOOL|OP_E2IO, BOOL|OP_E2IO, RL|OP_A2IO, RL|OP_A2, RL|OP_OP,
/* 45 */ RL, RL, LR|OP_OPF, LR|OP_OPF, RL|OP_A2,
@@ -1133,7 +1133,9 @@ op(int what)
* Any integer mod -1 is the same as any integer mod 1
* i.e. zero.
*/
- if (b.u.l == -1)
+ if (c.type == MN_FLOAT)
+ c.u.d = fmod(a.u.d, b.u.d);
+ else if (b.u.l == -1)
c.u.l = 0;
else
c.u.l = a.u.l % b.u.l;
next prev parent reply other threads:[~2015-01-11 7:10 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-09 12:43 PATCH: hist: remove wrong NULL terminator Mikael Magnusson
2015-01-09 17:45 ` Ray Andrews
2015-01-09 18:33 ` Lawrence Velázquez
2015-01-09 18:36 ` Lawrence Velázquez
2015-01-09 19:38 ` Mikael Magnusson
2015-01-09 21:39 ` Ray Andrews
2015-01-09 22:30 ` Peter Stephenson
2015-01-09 23:39 ` Ray Andrews
2015-01-10 0:39 ` Bart Schaefer
2015-01-10 7:45 ` Ray Andrews
2015-01-10 22:04 ` Lawrence Velázquez
2015-01-10 22:50 ` Ray Andrews
2015-01-11 1:58 ` Bart Schaefer
2015-01-11 5:46 ` Ray Andrews
2015-01-11 7:10 ` Bart Schaefer [this message]
2015-01-11 17:33 ` Floating point modulus Peter Stephenson
2015-01-11 19:25 ` Bart Schaefer
2015-01-11 19:25 ` Ray Andrews
2015-01-11 20:00 ` Bart Schaefer
2015-01-11 20:58 ` Ray Andrews
2015-01-11 21:34 ` Peter Stephenson
2015-01-12 0:18 ` Ray Andrews
2015-01-12 10:03 ` Peter Stephenson
2015-01-11 19:36 ` Bart Schaefer
2015-01-11 20:01 ` Peter Stephenson
2015-01-11 20:04 ` Bart Schaefer
2015-01-11 20:25 ` Peter Stephenson
2015-01-12 0:02 ` Ray Andrews
2015-01-12 2:23 ` Bart Schaefer
2015-01-12 2:46 ` Bart Schaefer
2015-01-12 9:56 ` Peter Stephenson
2015-01-12 13:49 ` Peter Stephenson
2015-01-12 16:35 ` Bart Schaefer
2015-01-12 16:45 ` Peter Stephenson
2015-01-12 11:36 ` Vincent Lefevre
2015-01-10 7:08 ` PATCH: hist: remove wrong NULL terminator Bart Schaefer
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