if { 0 } { Arjen Markus (18 february 2004) Several languages, among which Fortran 90, have array operations, to use Fortran 90 syntax:
real, dimension(1:100) :: a, b, c
b = 1.0
do i = 1,size(a)
a(i) = i
enddo
c= b / a would fill the array b with the value 1.0, in the do-loop each element of a is given a value (otherwise the last assignment is pretty dull) and each element of the array c is assigned the reciprocal value of the corresponding element of a.
In other words: arrays need not be manipulated only through do-loops (or for-loops, if you like).
This intrigued me: can we get the same thing into Tcl? The answer is obvious: yes!
The script below does very little error handling and it is currently limited to one-dimensional arrays (i.e., Tcl lists of simple numbers) only. But it is just a proof of concept :)
Note that arrays here are not Tcl's hash tables, but numerically indexed collections - for which one best uses lists in Tcl.
AM It is not always easy to come up with words that have an unambiguous meaning. I did not want to use "list" as that would have reminded people too much of other list operations...
See also the NAP package and the LA package (to a lesser extent).
}
# numarray.tcl --
# Array operations on lists of numbers
#
proc merge { list1 list2 } {
set result {}
foreach e1 $list1 e2 $list2 {
lappend result $e1 $e2
}
return $result
}
proc numrange { varname vmin vmax vstep } {
upvar $varname var
if { $vmax < $vmin } {
return -code error "Minimum must be smaller than maximum"
}
if { $vstep <= 0.0 } {
return -code error "Step must be positive"
}
set value $vmin
set var {}
while { $value < $vmax+0.5*$vstep } {
lappend var $value
set value [expr {$value+$vstep}]
}
}
proc numset { varname expression } {
upvar $varname var
#
# Replace the substrings "$var" by a corresponding
# list value - if the variable is a list
#
set _length_ 1
while { [string first \$ $expression] >= 0 } {
regexp {\$(\w+)} $expression ==> _v_
catch { upvar $_v_ $_v_ }
if { [llength [set $_v_]] > 1 } {
set _length_ [llength [set $_v_]]
regsub {\$\w+} $expression "\[lindex \@$_v_ @_i_\]" expression
} else {
regsub {\$\w+} $expression "@$_v_" expression
}
}
set expression [string map {@ $} $expression]
set _result_ {}
for { set _i_ 0 } { $_i_ < $_length_ } { incr _i_ } {
lappend _result_ [expr $expression]
}
set var $_result_
}
#
# Simple test cases
#
catch { console show }
numrange v 0.0 10.0 1.1
puts "v: $v"
numset w {$v*$v}
set p 1.0
numset v {$v+$w+$p}
puts "w: $w"
puts "v: $v"
#
# Now some graphics
#
package require Tk
numrange phi 0.0 [expr {2.0*3.1415926}] [expr {0.02*3.1415926}]
numset rad {1.0+cos($phi)}
numset x {100 + 100 * $rad * cos($phi)}
numset y {200 + 100 * $rad * sin($phi)}
pack [canvas .c -bg white -width 400 -height 400]
.c create line [merge $x $y]]