Tcl - a new example for data reformatting

Archive - Originally posted on "The Horse's Mouth" - 2015-10-10 06:23:31 - Graham Ellis
Tcl is an excellent language for combing through and reformatting data - though rarely a first choice language for such tasks if users aren't doing other things with it too.

Towards the end of last week's Learning to program in TCL course, a "side task" requirement came up to reformat our course diary into a .csv file so that a reseller who sells our courses to fill gaps / niches in his own more generic schedule.

Data of the form
30,11,2015 EL 8
needs to be transformed into data of the form

  ELFULL,30/11/2015,09:00,04/12/2015,17:00,Standard,1,1,SN12 7NY,En-GB,1350,1350,GBP,Well House,Learning to Program in Perl,Other (IT)Code

Complete program [here] and sample data [here].

The main code is as simple as

  loadDataWH "diary" intoHere

  saveDataQA "qa.csv" intoHere

so you can see that even in Tcl, we're using good, structured programming techniques - in this case letting me provide a number of different input formats and a number of output genereators.

Other points of note ...

• calculating end date from start date, allowing for month and year ends:

  set starts [clock scan "$day,$month,$year 12 00" -format "%d,%m,%Y %H %M"]

  set ends [expr $starts + ($courselength -1) * 3600 * 24]

  set eday [clock format $ends -format %e]

  set emonth [clock format $ends -format %m]

  set eyear [clock format $ends -format %Y]

reduces day, month, year of start to seconds from 1.1.1970, adds the number of days of the course (*3600*24) to make it seconds, and converts back. Much easier than trying to work out month lengths, especially for February in leap years.

• course names ending in "P" are 4 days and "L" are five days:

  set courselength 5

  set courseformat {Learning to Program in %s}

  if {[regexp {P$} $coursecode]} {

    set courselength 4

    set courseformat {%s Programming}

  }

• use of upvar to pass big chunks of data out of and into procs effectively and easily.

• allowing blank lines on input to be ignored

if {[string length $lyne] < 1} continue

• ... and many other useful techniques, worth a study!

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Tcl - a new example for data reformatting