--- rexxpub: defaults: rony.yaml logo: oorexx --- . slide cover # Procedural and Object-oriented Programming 6 . subtitle **Trace (Debug)** . cover-art . picture img/070_ooRexx_trace_debug_V14/p01-diagram-7.png . slide logo=rexx reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE – How Does Your Code Execute? . click - Understanding what your Rexx program does . after - Sometimes coding errors cannot be understood easily . click - Keyword statement **TRACE** and built-in function (BIF) **TRACE()** . after - Allows to temporarily have Rexx show in detail how it executes your statements . after - Allows to enter interactive mode that allows to inspect a specific location in your code . click - Most important options . plain steps level=2 | | | |---|---| | **N** | normal trace setting, only traces failures in commands | | **A** | show all statements that get executed | | **R** | show all statements and their final results | | **I** | show in detail all intermediate steps when executing a statement | . click - Prefixing an option with a question mark (**?**) causes **TRACE** to become interactive and to trace statements step by step at each press of the *\* key . after - Enter "**trace n**" to return to normal execution and stop interactive trace . slide reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE N – Example, 1 . after - Simple program, run twice with different output, default option **N** . after - Values change per run because of using the Rexx **random()**-BIF . after level=2 ```rexx /* default: "trace normal" in effect */ a=100+20 b=100+random(10,99) say "a*b:" a*b ``` . click level=2 Output of run # 1: . with level=2 ```output a*b: 16800 ``` . click level=2 Output of run # 2: . with level=2 ```output a*b: 17400 ``` . slide reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE A – Example, 2 . after - Running the program with **TRACE A** . after - Option **A** traces all statements (clauses) before execution . after group level=2 . after mark 1 pen=1 ```rexx { .numberLines } trace a /* show all statements */ a=100+20 b=100+random(10,99) say "a*b:" a*b ``` . end group . click label level=2 Output: . after steps=1,2,3,4 each=click level=2 ```output 2 *-* a=100+20 3 *-* b=100+random(10,99) 4 *-* say "a*b:" a*b a*b: 17040 ``` . slide reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE R – Example, 3 . after - Running the program with **TRACE R** . after - Option **R** traces all statements (clauses) and their final results . after group level=2 . after mark 1 pen=1 ```rexx { .numberLines } trace r /* show results */ a=100+20 b=100+random(10,99) say "a*b:" a*b ``` . end group . click label level=2 Output: . after steps=1-2,3-4,5-6,7 each=click level=2 ```output 2 *-* a=100+20 >>> "120" 3 *-* b=100+random(10,99) >>> "113" 4 *-* say "a*b:" a*b >>> "a*b: 13560" a*b: 13560 ``` . slide reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE I – Example, 4 . columns 6 6 . after - Running the program with **TRACE I** . after - Option **I** traces all intermediate results . after level=2 . after mark 1 pen=1 ```rexx { .numberLines } trace i /* show intermediates */ a=100+20 b=100+random(10,99) say "a*b:" a*b ``` . next column . click label Output: . after steps=7-16,17-23,24 each=click ```output 2 *-* a=100+20 >L> "100" >L> "20" >O> "+" => "120" >>> "120" >=> A <= "120" 3 *-* b=100+random(10,99) >L> "100" >L> "10" >A> "10" >L> "99" >A> "99" >F> RANDOM => "98" >O> "+" => "198" >>> "198" >=> B <= "198" 4 *-* say "a*b:" a*b >L> "a*b:" >V> A => "120" >V> B => "198" >O> "*" => "23760" >O> " " => "a*b: 23760" >>> "a*b: 23760" a*b: 23760 ``` . end columns . slide reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE I, TRACE N – Example, 5 . after - Running the program with **TRACE I** for tracing a single statement . after - **TRACE N** gets used to reset tracing to the default . after group level=2 . after mark 2 pen=1 . after mark 4 pen=1 ```rexx { .numberLines } a=100+20 trace i /* show intermediates */ b=100+random(10,99) trace n /* reset to normal */ say "a*b:" a*b ``` . end group . click label level=2 Output: . after steps=1-10,11,12 each=click ```output 3 *-* b=100+random(10,99) >L> "100" >L> "10" >A> "10" >L> "99" >A> "99" >F> RANDOM => "80" >O> "+" => "180" >>> "180" >=> B <= "180" 4 *-* trace n /* reset to normal */ a*b: 21600 ``` . slide reference="Cf. rexxref.pdf (2.29. TRACE, 7.4.66. TRACE)" # TRACE ?A – Example, 6 . after - Using **TRACE ?A** for tracing all statements in interactive mode . after - Interactive tracing allows for inspecting, changing values, tracing step by step . after group level=2 . after mark 1 pen=1 ```rexx { .numberLines } trace ?a /* show all statements, enter interactive mode */ a=100+20 b=100+random(10,99) say "a*b:" a*b ``` . end group . click label level=2 Output: . later id=#p8x17 numbered level=2 ```output +++ "WindowsNT COMMAND E:\tmp\06_ooRexx\19_trace_r_interactive.rex" 2 *-* a=100+20 +++ Interactive trace. "Trace Off" to end debug, ENTER to continue. +++ say a 120 a=100; trace r 3 *-* b=100+random(10,99) >>> "198" trace off a*b: 19800 ``` . click show #p8x17:1-3 . click show #p8x17:4 . click callout --> #p8x17:4 style="width:832px; max-width:none; box-sizing:border-box; font-size:19px" pin=top-left offset="311px 335px" Execution stops, manually adding a statement to display the current value of variable **a**, \ pressing ``{.key} continues. . click show #p8x17:5 . click show #p8x17:6 . click callout --> #p8x17:6 style="width:727px; max-width:none; box-sizing:border-box; font-size:19px" pin=top-left offset="418px 483px" Execution stops, manually adding two statements: changing variable **a** to **100** and\ changing tracing to trace results from now on, pressing ``{.key} continues. . click show #p8x17:7 . click show #p8x17:8 . click show #p8x17:9 . click callout --> #p8x17:9 style="width:649px; max-width:none; box-sizing:border-box; font-size:19px" pin=top-left offset="496px 554px" Execution stops, manually adding a single statement:\ set interactive tracing off, pressing ``{.key} continues. . click show #p8x17:10 . slide card logo=none # Contact