step -- step by single lines in the debugger

Usage:

step n
Inputs:
- n, an integer
Consequences:
- This command is active within the debugger. The current expression is executed and execution is continued until n lines of source code whose load depth is as large as errorDepth have been encountered. If n is omitted, then 1 is used. If n is negative then instead, n microsteps in the inner interpreter are executed and traced.

Description

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/demos/demo2.m2"

i2 : code f

o2 = ${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.
     m2:6:4-12:6: --source code:
     f = t -> (
          x := 1;
          error "debug me";
          y := t+1;
          z := 1/t;
          w := x+t;
          )

i3 : f 0
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:8:10:(3):[1]: error: debug me
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:8:10:(3): entering debugger (enter 'help' to see commands)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:8:5
-8:21: --source code:
     error "debug me";

ii4 : return
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:11:(3):[1]: --stepping limit reached
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:11:(3): entering debugger (enter 'help' to see commands)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:5
-9:13: --source code:
     y := t+1;

ii5 : current

oo5 = local-assign 2 0 2-OP + local-fetch 0 0
                              1

oo5 : PseudocodeClosure

ii6 : disassemble oo

oo6 = (local-assign 2 0 (2-OP + (local-fetch 0 0) 1))

ii7 : step(-3)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:11:(3):[1]: --evaluating: (local-assign 2 0 (2-OP + (local-fetch 0 0) 1))
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:11:(3):[1]: --evaluating: (2-OP + (local-fetch 0 0) 1)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:10:(3):[1]: --evaluating: (local-fetch 0 0)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:12:(3):[1]: --stepping limit reached
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:12:(3): entering debugger (enter 'help' to see commands)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:9:
12-9:13: --source code:
     y := t+1;

ii8 : step
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:10:11:(3):[1]: --stepping limit reached
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:10:11:(3): entering debugger (enter 'help' to see commands)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:10:
5-10:13: --source code:
     z := 1/t;

ii9 : step
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:10:11:(3):[1]: error: division by zero
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:10:11:(3): entering debugger (enter 'help' to see commands)
${prefix}/share/Macaulay2/Macaulay2Doc/demos/demo2.m2:10:
10-10:13: --source code:
     z := 1/t;

ii10 : t

oo10 = 0

For the programmer

The object step is a keyword.

The source of this document is in Macaulay2Doc/ov_debugging.m2:211:0.

step -- step by single lines in the debugger

Description

See also

For the programmer