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 |