.TH HAT-DETECT 1 local
.SH NAME
hat-detect \- find a bug by algorithmic debugging
.SH SYNOPSIS
.B hat-detect
prog[.hat]
.SH DESCRIPTION
.I hat-detect
is an interactive tool for finding bugs in the trace of a Haskell program
.I prog
supplied as its argument.  The user must answer a sequence of yes/no
questions.  Each question asked by hat-detect concerns the reduction
of a function application to a value.  You answer yes if the reduction
is correct with respect to your intentions, and <em>no</em> otherwise.
After a number of questions hat-detect reports an example equation
which is the cause of the observed faulty behaviour - that is, which
function definition is incorrect.

.SH INTERACTIVE COMMANDS
.PP
The hat-detect browser asks you questions, so the basic mode of
interaction is to type answers:
.TP
.B yes
Yes, the equation looks correct by my understanding of the meaning
of the function.
.TP
.B no
No, the equation looks incorrect.  Given the displayed arguments,
the function is returning the wrong result.
.PP
The following other commands are available.  They each begin with
a colon.
.TP
.B :show
Show the EDTs hat-detect is currently searching for bugs
.TP
.B :children
Show the children of the current reduction.

.TP
.B :quit
Exit the interactive tool.
.TP
.B :help
Shows help text giving an overview of the commands available.

.TP
.B :source
Shows (in a separate window) the source code for the reduction currently being queried.
.TP
.B :delta
Start the hat-delta browser in a new window, beginning with the currently
queried reduction.
.TP
.B :detect
or
.B :split
Start the hat-detect browser in a new window, beginning with the currently
queried reduction.
.TP
.B :explore
Start the hat-explore browser in a new window, beginning with the currently
queried reduction.
.TP
.B :trail
Start a hat-trail browser in a new window, beginning with the currently
queried reduction.


.SH FILES
.TP 25
.B @BINDIR@/hat-detect

.SH "SEE ALSO"
hmake(1), hat-trans(1), hat-delta(1), hat-stack(1), hat-observe(1), hat-trail(1)