One useful way to debug code suspected of being in error is to insert an explicit error message, such as error "debug me", and start stepping from there, as in the following demonstration.
i1 : load "Macaulay2Doc/demo2.m2" |
i2 : code f o2 = /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:6:7-12:13: --source code: f = t -> ( x := 1; error "debug me"; y := t+1; z := 1/t; w := x+t; ) |
i3 : f 0 /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:8:6:(3):[1]: error: debug me /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:8:6:(3):[1]: --entering debugger (type help to see debugger commands) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:8:6-8:6: --source code: error "debug me"; |
ii4 : help --loading the Macaulay2 documentation from /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/ oo4 = --debugging control: return -- bypass current expression, return null, stop return x -- bypass current expression, return x, stop step -- step 1 line step n -- step n lines step (-n) -- trace n microsteps end (or eof char) -- enter debugger one level up continue -- leave the debugger, continuing execution -- with current expression break -- leave the debugger, returning to top level --debugging information: listLocalSymbols -- display local symbols and their values listUserSymbols -- display user symbols and their values current -- the current expression; initially, the one -- that produced an error code current -- source code of current expression value current -- execute current expression, obtain value disassemble current -- display microcode of current expression currentString -- the string being evaluated by 'value', if -- an error occurred within it -- emacs commands in *M2* buffer: RET -- on an file/position line, go to source |
ii5 : return /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:8:(3):[1]: --stepping limit reached /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:8:(3):[1]: --entering debugger (type help to see debugger commands) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:8-9:13: --source code: y := t+1; |
ii6 : disassemble current oo6 = (store 2 0 (2-OP + (fetch 0 0) 1)) |
ii7 : step(-3) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:8:(3):[1]: --evaluating: (store 2 0 (2-OP + (fetch 0 0) 1)) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:12:(3):[1]: --evaluating: (2-OP + (fetch 0 0) 1) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:11:(3):[1]: --evaluating: (fetch 0 0) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:13:(3):[1]: --stepping limit reached /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:13:(3):[1]: --entering debugger (type help to see debugger commands) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:9:13-9:13: --source code: y := t+1; |
ii8 : step /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:10:8:(3):[1]: --stepping limit reached /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:10:8:(3):[1]: --entering debugger (type help to see debugger commands) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:10:8-10:13: --source code: z := 1/t; |
ii9 : step /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:10:12:(3):[1]: error: division by zero /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:10:12:(3):[1]: --entering debugger (type help to see debugger commands) /builddir/build/BUILD/Macaulay2-1.3.1-r10737/Macaulay2/packages/Macaulay2Doc/demo2.m2:10:11-10:13: --source code: z := 1/t; |
ii10 : t oo10 = 0 |