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Operating Systems OS X (Apple) A fixed point basic calculator for DASH. Post 303025593 by wisecracker on Tuesday 6th of November 2018 02:03:46 PM
Old 11-06-2018
Quote:
Originally Posted by Corona688
Your use of printf "%f" is perhaps begging for trouble, that may convert to floating point and back. And even 64-bit floating point doesn't have the exactness of a 64-bit integer, some of those 64 bits get dedicated to mantissa et cetera.

dash gives +224466891.896745235 on my system, bash and ksh give +224466891.896745230, and zsh doesn't work at all, it gives "invalid floating point number" on printf "%s%.9f\n" "$MINUS" "$RESULT"
I wouldn't know where to start for floating point maths in pure 'dash' and I'll stick my neck out and say it cannot be done at all.

I don't use "%f" anywhere, I use "%.f" instead and 'shellcheck' shows no issues using 'dash' as the shell and changing it to 'sh' too.

I did quote that up 1,000,000.000000000, (1 Million), it is accurate to 9 decimal places and gets progressively worse to the upper/lower limits. Therefore IMO 8 places accuracy to at least 22 Million is acceptable for ordinary work

As for the code snippets I will try them out whilst working out multiply and divide; and I thought 'add' and 'subtract' were hard.
Doing it on the command line is not the same as working out the algorithms for limited language like 'dash'. All those 'bash'isms one takes for granted.

I have no idea why 'zsh' fails when the others work as per POSIX, I don't really intend to find out as dash is the important shell ATM...
(I have not got 'ash' so dunno if it works on that.)

EDIT:
Done manually...
Code:
Last login: Tue Nov  6 19:05:47 on ttys000
AMIGA:amiga~> cd Desktop/Code/Shell
AMIGA:amiga~/Desktop/Code/Shell> ./calc .000000277 - +.000000092
+0.000000185
AMIGA:amiga~/Desktop/Code/Shell> # Therefore SUM="000000185"
AMIGA:amiga~/Desktop/Code/Shell> FLOAT="000000185"
AMIGA:amiga~/Desktop/Code/Shell> INT=""
AMIGA:amiga~/Desktop/Code/Shell> NUMBER=$(( FLOAT/100 ))
-bash: 000000185: value too great for base (error token is "000000185")
AMIGA:amiga~/Desktop/Code/Shell> dash
AMIGA:\u\w> ./calc .000000277 - +.000000092
+0.000000185
AMIGA:\u\w> # Therefore SUM="000000185"
AMIGA:\u\w> FLOAT="000000185"
AMIGA:\u\w> INT=""
AMIGA:\u\w> NUMBER=$(( FLOAT/100 ))
dash: 6: Illegal number: 000000185
AMIGA:\u\w> exit
AMIGA:amiga~/Desktop/Code/Shell> _

Bazza...

Last edited by wisecracker; 11-06-2018 at 03:37 PM.. Reason: Manual reason for not using 'x%100'.
 

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Tk_GetDash(3)						       Tk Library Procedures						     Tk_GetDash(3)

__________________________________________________________________________________________________________________________________________________

NAME
Tk_GetDash - convert from string to valid dash structure. SYNOPSIS
#include <tk.h> int Tk_GetDash(interp, string, dashPtr) ARGUMENTS
Tcl_Interp *interp (in) Interpreter to use for error reporting. const char * string (in) Textual value to be converted. Tk_Dash *dashPtr (out) Points to place to store the dash pattern value converted from string. _________________________________________________________________ DESCRIPTION
These procedure parses the string and fills in the result in the Tk_Dash structure. The string can be a list of integers or a character string containing only ".,-_" or spaces. If all goes well, TCL_OK is returned. If string does not have the proper syntax then TCL_ERROR is returned, an error message is left in the interpreter's result, and nothing is stored at *dashPtr. The first possible syntax is a list of integers. Each element represents the number of pixels of a line segment. Only the odd segments are drawn using the "outline" color. The other segments are drawn transparent. The second possible syntax is a character list containing only 5 possible characters ".,-_ ". The space can be used to enlarge the space between other line elements, and can not occur as the first position in the string. Some examples: -dash . = -dash {2 4} -dash - = -dash {6 4} -dash -. = -dash {6 4 2 4} -dash -.. = -dash {6 4 2 4 2 4} -dash {. } = -dash {2 8} -dash , = -dash {4 4} The main difference of this syntax with the previous is that it is shape-conserving. This means that all values in the dash list will be multiplied by the line width before display. This assures that "." will always be displayed as a dot and "-" always as a dash regardless of the line width. On systems where only a limited set of dash patterns, the dash pattern will be displayed as the most close dash pattern that is available. For example, on Windows only the first 4 of the above examples are available. The last 2 examples will be displayed identically as the first one. KEYWORDS
dash, conversion Tk 8.3 Tk_GetDash(3)
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