This is a little utility to help generating a lot of similar procs or methods that might be necessary when evaluating a Parser Tools peg grammar.
#!/usr/bin/env tclkit8.6
#
# parser-actions.tcl
#
# Many parser generators allow code to be associated with the grammar rules and
# executed as the rules are recognized. This script is a helper program to allow
# action templates to be associated with [Parser Tools] peg grammar rules.
#
# When the peg parser returns the AST, it is executed as a tcl script. This
# allows the names of the PEG rules to be directly used as parser actions. Each
# parser rule corresponds to a proc (or method) of the parser. In the grammar there
# are many rules which share the same code, specifically many non-terminal rules whose
# value is the concatenated values of their child rules and leaf rules whose values
# are the underlying string or token that the rule matched.
#
# This proc allows the grammar file to "declare" the type of a rule in a following
# comment. The rule type is then associated with a template for that type and the
# method is declared with the rule/action name and the code from the template.
#
proc parser-actions { file actions } {
set reply {}
foreach line [split [read [open $file]] \n] {
switch -regexp -matchvar match $line {
{ *([a-zA-Z0-9_]+)[ \t]*<-[^;]*; *# *action ([a-zA-Z0-9_]+)[ \t]*} {
append reply [string map [list %action [lindex $match 1]] \
[dict get $actions [lindex $match 2]]] \n
}
{ *([a-zA-Z0-9_]+)[ \t]*<-} { set action [lindex $match 1] }
{; *# *action ([a-zA-Z0-9_]+)[ \t]*$} {
append reply [string map [list %action $action] \
[dict get $actions [lindex $match 1]]] \n
}
}
}
set reply
}
set parser [lindex $argv 0] ;# A [Parser Tools] peg file w/annotations in comments.
set action [lindex $argv 1] ;# A file containing a dict of template procs.
puts [parser-actions $parser \
[regsub -all -line -- {((^[ \t]*)|([ \t]+))#.*$} [read [open $action]] { }]]