foreach - tcl data formats confusion -

the motivation behind question learning...

i have done tcl programming , have working code, not understand why syntax working , not.

problem description: i'm writing code needs set voltages power , ground nets. after enter vdd nets string,

set power_nets "vdd=1.1 vdda=1.2 vref=1.1" 

then simple tcl code should construct , execute following commands:

set_vdd vdd 1.1 set_vdd vdda 1.2 set_vdd vref 1.1 

that all. seems trivial, have had difficulty implementing it. still not understand why code not work, although seems correct me.

working solution: working solution came following:

foreach item [split $power_nets] {     set net [lindex [split $item =] 0]     set voltage [lindex [split $item =] 1]     set_vdd $net $voltage } 

that's lot of code such simple operation. when written in more condensed form still works:

foreach item [split $power_nets] {     set_vdd [lindex [split $item =] 0] [lindex [split $item =] 1] } 

but still have feeling there room improvement here.

learning objective: settle solution optimal code (it both short , comprehensive)

foreach item [split $power_nets] {     set_vdd [split $item =] } 

unfortunately not work. tool interprets set_vdd command complains that

no value given parameter "voltage" (use -help full usage) : 

i not understand why not work. difference?

when replace set_vdd puts, print values. information there. isn't it?

nlv12345@acc3081 char_out_logs $ tclsh % set power_nets "vdd=1.1 vdda=1.2 vref=1.1" vdd=1.1 vdda=1.2 vref=1.1 % foreach item [split $power_nets] {     puts [split $item =] } vdd 1.1 vdda 1.2 vref 1.1 %  

the error message less optimal, problem you're passing 2 words out of split single argument set_vdd.

if tcl interpreter currently-supported version, can instead this:

foreach item [split $power_nets] {     set_vdd {*}[split $item =] } 

the {*} marker “take list — rest of word — , split separate arguments”. while it's formally not operator rather syntactic part of tcl language, calling “expansion operator” won't confuse lot.

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older, unsupported versions of tcl (8.4 , before) require use of eval this. you're ok with:

foreach item [split $power_nets] {     eval set_vdd [split $item =] } 

but safer this:

foreach item [split $power_nets] {     eval [linsert [split $item =] 0 set_vdd] } 

as can see, {*} simplifies things quite bit.

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however, i'd this:

foreach {item key value} [regexp -all -inline {(\w+)=([\d.]+)} $power_nets] {     set_vdd $key $value } 

like that, unexpected things in power_nets value won't cause trouble. otoh, if you're not used regular expressions perhaps not time start regexp…