[Richard Suchenwirth] - Tcl is somehow more than just a programming language. At times it feels like a quite powerful operating system, with commands that have their own "small languages" (''sed'', ''awk'' in Unix; [expr], [regexp]... in Tcl). But while implementing ''sed''s or ''awk''s functionality in C is hard work, in Tcl the creation of a custom "small language" is made easy by strong string processing commands. Hence I chose a small math language for my New Year's Eve fun project. The accepted language is based on [expr]'s, which is well known to Tcl'ers and able to express all C arithmetics (and more), so isn't exactly small. However, I added some functionalities discussed earlier on [the comp.lang.tcl newsgroup], plus some sugar to make it look more similar to conventional math notation: * allow multiple expressions, separated by semicolon * allow one infix assignment per expression, like ''i = j + 1'' * allow references to existing variables without prefixed dollar sign * allow omission of parens around simple function arguments * allow omission of the * operator after numeric constants * allow one fraction to be written with horizontal bar instead of / These effects took little effort, as they were reached by string manipulations on the arguments to ''math'', which transform them to valid [expr] language, and evaluate that in caller's scope. On the other hand, no tokenization like that of [expr] was done (where ''$i+$j'' is equivalent to ''$i + $j''), so the arguments have to be list elements separated by whitespace. At the place marked "more preprocessing here", you can add your own ideas. See the usage examples at end, and enjoy! proc math args { if {[llength $args]==1} {set args [lindex $args 0]} foreach mathcmd [split $args ";"] { set cmd "" if {[lindex $mathcmd 1]=="="} { set cmd [list set [lindex $mathcmd 0]] set expr [lrange $mathcmd 2 end] } else {set expr $mathcmd} set expr2 "expr \{(" set previous "" foreach i $expr { if [uplevel 1 info exists $i] {set i \$$i} if [regexp -- {--+} $i] {set i )/double(} if [isBuiltin $previous] {set i ($i)} if {[isNumeric $previous] && [regexp {^[$A-Za-z�_]} $i]} { set i *$i } # more preprocessing here.. set previous $i append expr2 $i } append expr2 ")\}" if {$cmd==""} { set cmd $expr2 } else { append cmd " \[$expr2\]" } set res [uplevel 1 $cmd] } set res ;# return last expression's result } proc isBuiltin word { expr [lsearch -exact { abs cosh log sqrt acos double log10 srand asin exp pow tan atan floor rand tanh atan2 fmod round ceil hypot sin cos int sinh} $word ]>=0 } proc isNumeric x {expr ![catch {expr $x*1}]} # testing, and usage examples: math { a = 1 * (2 - 1); b = sqrt 4; c = 3 a - b ------- a + b } puts c:$c ---- [Salt and Sugar] - [Arts and crafts of Tcl-Tk programming]