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From: eric.boudaillier@gmail.com (eric)
Newsgroups: comp.lang.tcl
Subject: Re: good to know: tcl static "regexp" is faster than tcl "string" operation
Date: Thu, 2 Jan 2025 11:04:50 +0000
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On Tue, 31 Dec 2024 18:33:41 +0000, aotto1968 wrote:

> ....
> On 31.12.24 14:46, Rich wrote:
>>
>> But neither is quite as fast as string match (athough regex is close):


This kind of regexp generates bytecode using string match instead.
The time difference between both is due to the if-else construct.

tcl::unsupported::disassemble proc test-1
ByteCode 0x0450C010, refCt 1, epoch 18, interp 0x0442C8C0 (epoch 18)
  Source "\n   if {[regexp ^:: $val]} {\n     return true\n   } e..."
  Cmds 4, src 81, inst 36, litObjs 3, aux 0, stkDepth 2, code/src 0.00
  Proc 0x04551488, refCt 1, args 1, compiled locals 1
      slot 0, scalar, arg, "val"
  Commands 4:
      1: pc 0-34, src 4-79        2: pc 0-5, src 9-23
      3: pc 9-20, src 34-44        4: pc 23-34, src 63-74
  Command 1: "if {[regexp ^:: $val]} {\n     return true\n   } else
{..."
  Command 2: "regexp ^:: $val..."
    (0) push1 0 	# "::*"
    (2) loadScalar1 %v0 	# var "val"
    (4) strmatch +0
    (6) nop
    (7) jumpFalse1 +16 	# pc 23
  Command 3: "return true..."
    (9) startCommand +12 1 	# next cmd at pc 21, 1 cmds start here
    (18) push1 1 	# "true"
    (20) done
    (21) jump1 +14 	# pc 35
  Command 4: "return false..."
    (23) startCommand +12 1 	# next cmd at pc 35, 1 cmds start here
    (32) push1 2 	# "false"
    (34) done
    (35) done

Eric

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