Tcl

Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Demonstrates replacing capture groups for a regular expression.

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Tcl

load ./chilkat.dll

set success 0

set subject "John Anders, +_+_+ Mary Robins $$$$"
set pattern "(?<first>\\w+)\\s+(?<last>\\w+)"

set sb [new_CkStringBuilder]

CkStringBuilder_Append $sb $subject

set json [new_CkJsonObject]

CkJsonObject_put_EmitCompact $json 0

set timeoutMs 2000
set numMatches [CkStringBuilder_RegexMatch $sb $pattern $json $timeoutMs]
if {$numMatches < 0} then {
    # Probably an error in the regular expression.
    # Suggestion: Use AI to help create and/or diagnose regular expressions.
    puts [CkStringBuilder_lastErrorText $sb]
    delete_CkStringBuilder $sb
    delete_CkJsonObject $json
    exit
}

# Examine the matches:
puts [CkJsonObject_emit $json]

# There are 2 matches:

# {
#   "named": {
#     "first": 1,
#     "last": 2
#   },
#   "match": [
#     {
#       "group": [
#         {
#           "cap": "John Anders",
#           "idx": 0,
#           "len": 11
#         },
#         {
#           "cap": "John",
#           "idx": 0,
#           "len": 4
#         },
#         {
#           "cap": "Anders",
#           "idx": 5,
#           "len": 6
#         }
#       ]
#     },
#     {
#       "group": [
#         {
#           "cap": "Mary Robins",
#           "idx": 19,
#           "len": 11
#         },
#         {
#           "cap": "Mary",
#           "idx": 19,
#           "len": 4
#         },
#         {
#           "cap": "Robins",
#           "idx": 24,
#           "len": 6
#         }
#       ]
#     }
#   ]
# }

# To replace capture groups, write code to examine each capture group within
# each match, and provide a replacement string.
# Then call RegexReplace.

# For example, let's capitalize the first names, and add append "on" to the last name.
# After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

set firstNameIdx [CkJsonObject_IntOf $json "named.first"]
set lastNameIdx [CkJsonObject_IntOf $json "named.last"]

set sbTemp [new_CkStringBuilder]

set i 0
set numMatches [CkJsonObject_SizeOfArray $json "match"]
while {$i < $numMatches} {

    CkJsonObject_put_I $json $i

    # The replacement string for the first name will be all uppercase.
    CkJsonObject_put_J $json $firstNameIdx
    CkStringBuilder_Clear $sbTemp
    CkJsonObject_StringOfSb $json "match[i].group[j].cap" $sbTemp
    CkStringBuilder_ToUppercase $sbTemp
    CkJsonObject_UpdateSb $json "match[i].group[j].rep" $sbTemp

    # Append "on" to the last name.
    CkJsonObject_put_J $json $lastNameIdx
    CkStringBuilder_Clear $sbTemp
    CkJsonObject_StringOfSb $json "match[i].group[j].cap" $sbTemp
    CkStringBuilder_Append $sbTemp "on"
    CkJsonObject_UpdateSb $json "match[i].group[j].rep" $sbTemp

    set i [expr $i + 1]
}

# The JSON now has replacement strings:
puts [CkJsonObject_emit $json]

# {
#   "named": {
#     "first": 1,
#     "last": 2
#   },
#   "match": [
#     {
#       "group": [
#         {
#           "cap": "John Anders",
#           "idx": 0,
#           "len": 11
#         },
#         {
#           "cap": "John",
#           "idx": 0,
#           "len": 4,
#           "rep": "JOHN"
#         },
#         {
#           "cap": "Anders",
#           "idx": 5,
#           "len": 6,
#           "rep": "Anderson"
#         }
#       ]
#     },
#     {
#       "group": [
#         {
#           "cap": "Mary Robins",
#           "idx": 19,
#           "len": 11
#         },
#         {
#           "cap": "Mary",
#           "idx": 19,
#           "len": 4,
#           "rep": "MARY"
#         },
#         {
#           "cap": "Robins",
#           "idx": 24,
#           "len": 6,
#           "rep": "Robinson"
#         }
#       ]
#     }
#   ]
# }

# Call RegexReplace to update the StringBuilder with the replacements.
set success [CkStringBuilder_RegexReplace $sb $json]
if {$success == 0} then {
    puts [CkStringBuilder_lastErrorText $sb]
    delete_CkStringBuilder $sb
    delete_CkJsonObject $json
    delete_CkStringBuilder $sbTemp
    exit
}

puts "Result after doing replacements:"
puts [CkStringBuilder_getAsString $sb]

# Result after doing replacements:
# JOHN Anderson, +_+_+ MARY Robinson $$$$

delete_CkStringBuilder $sb
delete_CkJsonObject $json
delete_CkStringBuilder $sbTemp